Abstract
There are no evidence-based guidelines as to whether computed tomography (CT) or endoscopy should be selected as the first-line procedure when a nasal tumor is suspected in a dog or a cat and only one examination can be performed. Computed tomography and rhinoscopic features of 17 dogs and 5 cats with a histopathologically or cytologically confirmed nasal tumor were retrospectively reviewed. The level of suspicion for nasal neoplasia after CT and/or rhinoscopy was compared to the definitive diagnosis. Twelve animals underwent CT, 14 underwent rhinoscopy, and 4 both examinations. Of the 12 CT examinations performed, 11 (92%) resulted in the conclusion that a nasal tumor was the most likely diagnosis compared with 9/14 (64%) for rhinoscopies. Computed tomography appeared to be more reliable than rhinoscopy for detecting nasal tumors and should therefore be considered as the first-line procedure.
Résumé
Examen de première intention lors de suspicion de tumeur nasale: scanner où rhinoscopie? Une étude pilote. Lors de suspicion de tumeur nasale chez le chien et le chat, il n’existe à ce jour aucun consensus quant à l’examen de première intention à privilégier entre la tomodensitométrie et l’endoscopie lorsqu’un seul examen peut être réalisé. Les caractéristiques tomodensitométriques et endoscopiques de 17 chiens et 5 chats avec un diagnostic de tumeur nasale confirmé histologiquement ou cytologiquement ont été analysées rétrospectivement. Le degré de suspicion de tumeur nasale permis par l’endoscopie et/ou le scanner a été comparé au diagnostic final. Un examen tomodensitométrique a été réalisé chez 12 animaux, une rhinoscopie chez 14 et les deux examens ont été couplés dans quatre cas. L’examen scanner a conclu qu’une tumeur nasale était le diagnostic le plus probable dans 11 cas sur 12 (92 %), et la rhinoscopie dans 9 cas sur 14 (64 %). L’examen scanner apparait plus fiable que la rhinoscopie pour détecter les tumeurs nasales, et de ce fait devrait être considéré comme le meilleur examen de première intention.
(Traduit par les auteurs)
Introduction
Primary nasal tumors are rare, but they constitute 70% of chronic nasal diseases in dogs and 40% in cats (1,2). Early diagnosis facilitates therapy and improves prognosis (3). Suspicion of a nasal tumor is based on history, clinical signs, and clinical examination. Endoscopy and computed tomography (CT) of the nasal cavity both provide useful information for the diagnostic and therapeutic plan, even if the definitive diagnosis requires histopathological or cytopathological analyses. Rhinoscopy allows direct gross visualization of the nasal mucosa and visual control of biopsy (4,5). Computed tomography allows evaluation of bone integrity with bone lysis being strongly associated with nasal tumors (3,6,7). It also provides an accurate assessment of the extent and metastatic spread of the tumor to regional lymph nodes and the lung field, and is useful for planning radiation therapy (8–11).
For financial reasons, it is not always possible to perform both CT and rhinoscopy in a patient with a suspected nasal tumor. The major concern of some owners is to investigate the possibility of a neoplasm, the answer determining their willingness to pursue subsequent examinations and treatments. Rhinoscopy and CT are also not always both available. There is no consensus as to whether CT or rhinoscopy is the best first-line procedure when a nasal tumor is considered.
The objective of this retrospective study was to compare the level of suspicion of a nasal neoplasm obtained by CT and/or rhinoscopy in 17 dogs and 5 cats with a final histopathological or cytological diagnosis of nasal neoplasia, in an effort to provide preliminary recommendations for practioners suspecting a nasal neoplasm and dealing with the choice between the 2 procedures.
Materials and methods
Dogs and cats with primary nasal tumors diagnosed histologically or cytologically from 2007 to 2010 were eligible for inclusion, provided that they had also undergone CT examination of the nasal cavities and/or rhinoscopy. Twenty-two cases were selected; 12 underwent CT, 14 rhinoscopy, and 4 both examinations.
The following characteristics at first presentation were extracted from the database for each patient: signalment, systemic clinical signs, respiratory signs (nasal discharge, sneezing, dyspnea, stertor, coughing), facial distortion, epiphora, and mandibular lymphadenomegaly. Final diagnosis was obtained by sampling during rhinoscopy or immediately after CT examination. For the patients that had both examinations, rhinoscopy was performed immediately after CT. For the patients that had surgical tumor removal leading to subsequent histopathological diagnosis, the surgery was performed less than 19 d after CT examination or rhinoscopy. All histological and cytological material was assessed by a board-certified pathologist or a senior pathologist with > 20 years experience in endoscopic biopsy reading. The tumor type was retrieved from the cytological or histological reports.
All CT examinations were performed with the patient under general anesthesia, using a helical 2-slice CT scanner (GE HiSpeed NX/i Pro; Network Imaging Systems, Charlotte, North Carolina, USA) 120kV, 440 mA, rotation 0.7s. Computed tomographic acquisitions were performed before and after IV injection of iodinated contrast medium (iohexol Omnipaque® 240 mg/mL; GE Healthcare, Princeton, New Jersey, USA) at 2 mL/kg body weight (BW). Slice thickness varied from 1 mm to 3 mm according to patient size. Computed tomographic data were all interpreted at the time of original examination by the same radiologist and before a histopathological diagnosis was made. Computed tomography reports and CT images were retrospectively reviewed independently by 2 of the authors (MF and MH) in 2-steps.
The first step was to record the following CT characteristics for each case: bone lysis (nasal turbinates, paranasal bones, vomer bone, nasal septum, and cribriform plate); mass-like effect in nasal cavity; lateralization of bony and nasal tissue lesions; presence of abnormal soft tissue attenuation in sinuses, nasopharynx, retrobulbar space, maxillary recesses and tympanic bullae; features consistent with metastatic spread to mandibular and retropharyngeal lymph nodes. Lymph node characteristics suspicious of malignancy were defined as heterogeneous contrast enhancement and enlargement. Enhancement characteristics of nasal and sinus lesions were classified as none or present, and the enhancing pattern as heterogeneous or homogeneous.
In the next step, reviewers classified the lesions for each animal as being highly suggestive of a nasal tumor, consistent with a nasal tumor, or providing no evidence of a nasal tumor. This was based on the radiological reports as well as the retrospectively analyzed images and CT features discussed. In cases of disagreement, a consensus was reached. The CT features considered as highly suggestive of a nasal neoplasm were extensive lysis of bone and nasal turbinates associated with an ipsilateral soft-tissue attenuating mass-effect in the nasal cavity, possibly associated with local or regional lymphadenopathy. Computed tomography features consistent with a nasal neoplasm were a soft-tissue mass effect in the nasal cavity associated with minimal or no lysis of bone and turbinates and without any sign of metastatic spread (6,12,13). Computed tomographic features were considered not to be consistent with a nasal tumor when no sign of a nasal soft tissue mass or bony involvement was seen, but there was at least 1 of turbinate destruction without mass effect, mucosal thickening, sinusal or choanal lesions.
Rhinoscopy was performed under general anesthesia. One of 2 internists, who each had > 10 y experience using endoscopy, performed the rhinoscopic examinations. An anterograde approach with a rigid endoscope (Optomed®; 21 cm length, 3.5 mm diameter, 2 mm canal diameter; Les Ulis, France) was combined with a retrograde approach with a flexible endoscope (Optomed® type VO-143; 140 cm length, 9.8 mm diameter, 2.8 mm canal diameter) for dogs weighing more than 15 kg; Optomed® type EF-B14L; 70 cm length, 3.7 mm diameter for cats and dogs weighing < 15 kg. Endoscopic reports at the time of the original examination associated with rhinoscopic static images were retrospectively reviewed independently by 2 of the authors (MF and MH).
The first step was to record for each patient the following features: abnormalities of the nasal mucosa (well-circumscribed mass, diffuse rough proliferative appearance, diffuse erosive appearance, and hyperemia), presence of exudates and lateralization of these lesions.
For the next step, reviewers classified the lesions for each animal as being highly suggestive of a nasal tumor, consistent with a nasal tumor, or providing no evidence of a nasal tumor. This was based on the endoscopic reports and the retrospectively analyzed rhinoscopic features discussed. In case of disagreement, a consensus was reached. The rhinoscopic features that were highly suggestive of a nasal neoplasm were a well-circumscribed mass identified by anterograde or retrograde approach. Rhinoscopic features consistent with a nasal tumor were a diffuse rough proliferative appearance of the mucosa without any well-circumscribed mass or an erosive appearance of the mucosa without any evidence of a fungal plaque lesion. A nasal neoplasm was considered unlikely when the nasal mucosa appeared inflammatory (edema, hyperemia) without any mass lesion or erosion (4,14).
For the 4 patients that underwent both procedures, the results of the 2 examinations were analyzed separately by 2 of the authors (MH and MF), as previously described.
The error frequencies of diagnostic conclusions stated after CT and rhinoscopy were compared using Fisher’s test. For statistical analysis P ≤ 0.05 was considered significant.
Results
Medical records of 40 patients presented for chronic nasal disease and with nasal neoplasia being the main differential diagnosis after initial clinical examination over a 3-year period were reviewed. Eighteen patients did not fulfil the inclusion criteria; 2 had a maxillary bony neoplasm associated with secondary nasal invasion and 16 did not have histological or cytological confirmation of a nasal neoplasm. Records for the remaining 22 patients (17 dogs and 5 cats) were reviewed. All the included dogs belonged to dolichocephalic or mesocephalic breeds: there were 4 terriers (23.5%), 3 German shepherd dogs (17.6%), one each of the following breeds of dogs: golden retriever, Labrador retriever, Weimaraner, poodle, collie, doberman, dogo Argentino, Tibetan spaniel, and 2 crossbreeds. Two of the 5 cats belonged to brachycephalic breeds: 1 Persian and 1 British shorthair. The 3 other cats were domestic shorthairs.
There were 12 male dogs (70.6%), 6 entire, 3 neutered and 3 of unknown status; 5 female dogs (29.4%), 1 entire, 1 neutered, and 3 of unknown status; 3 neutered male cats and 2 female cats, 1 neutered and 1 entire. The dogs were between 5.8 y and 13.2 y old [mean +/− standard deviation (SD) = 10.1 y +/− 2.2 y] and the cats between 2.1 y and 14.1 y old (mean +/− SD = 9.2 y +/− 4.8 y).
Final diagnosis was obtained by endoscopy-guided biopsy (n = 11), histology of a nasal mass extracted by nasal flushing (n = 1), surgical biopsy (n = 2, one of whom also had previous conclusive endoscopy guided-biopsy), CT-guided fine-needle aspiration (FNA) of a nasal lesion (n = 4), blinded biopsy with rhinoscopic biopsy forceps (n = 2), postmortem examination (n = 1) or FNA of a regional mandibular lymph node (n = 1). Eighteen of 22 patients (81.8%) were diagnosed with nasal carcinoma (7 adenocarcinomas, 5 transitional carcinomas, 2 squamous cell carcinomas, 2 neuro-endocrinal carcinomas, 1 anaplastic carcinoma, and 1 carcinoma of undetermined type). Three patients (13.6%) were diagnosed with nasal sarcoma and 1 cat (4.5%) with nasal B-cell lymphoma (Table 1).
Table 1.
Comparative morphologic diagnosis, rhinoscopy, and computed tomography conclusions
| Patient, species | Morphologic diagnosis | Endoscopy conclusion | Computed tomography conclusion |
|---|---|---|---|
| 1, dog | Adenocarcinoma | No evidence | Consistent with |
| 2, dog | Neuro-endocrinal carcinoma | No evidence | Consistent with |
| 3, dog | Carcinoma | Highly suggestive | Highly suggestive |
| 4, cat | Adenocarcinoma | Highly suggestive | No evidence |
| 5, dog | Transitional carcinoma | Highly suggestive | |
| 6, dog | Adenocarcinoma | Highly suggestive | |
| 7, cat | Adenocarcinoma | Highly suggestive | |
| 8, dog | Adenocarcinoma | Consistent with | |
| 9, doga | Transitional carcinoma | No evidence | Consistent with |
| 10, dog | Transitional carcinoma | Consistent with | |
| 11, dog | Adenocarcinoma | Highly suggestive | |
| 12, dog | Transitional carcinoma | Highly suggestive | |
| 13, dog | Adenocarcinoma | No evidence | |
| 14, cat | Sarcoma | No evidence | |
| 15, dog | Sarcoma | Consistent with | |
| 16, dog | Squamous cell carcinoma | Consistent with | |
| 17, dog | Neuro-endocrinal carcinoma | Highly suggestive | |
| 18, dog | Squamous cell carcinoma | Highly suggestive | |
| 19, cat | Anaplastic carcinoma | Consistent with | |
| 20, dog | Sarcoma | Highly suggestive | |
| 21, cat | B-cell lymphoma | Highly suggestive | |
| 22, dog | Transitional carcinoma | Highly suggestive |
No evidence = No evidence for a tumor; Consistent with = Consistent with a tumor; Highly suggestive = Highly suggestive of a tumor.
This patient had 2 successive rhinoscopic examinations (1 and 2).
Clinical signs at first presentation (Table 2)
Table 2.
Clinical signs at first presentation
| Clinical signs | Animals with CT (n = 12) (%) | Animals with rhinoscopy (n = 14) (%) | Total of affected animals (n = 22) (%) |
|---|---|---|---|
| Respiratory signs | 12/12 (100) | 14/14 (100) | 22/22 (100) |
| Chronic nasal discharge | 11/12 (91.6) | 13/14 (92.9) | 21/22 (95.5) |
| Unilateral | 8/12 (66.7) | 6/14 (42.9) | 12/22 (57.1) |
| Hemorrhagic | 10/12 (83.3) | 8/14 (57.1) | 16/22 (76.2) |
| Serous | 4/12 (33.3) | 7/14 (50) | 10/22 (47.6) |
| Mucopurulent | 7/12 (58.3) | 4/14 (28.6) | 9/22 (42.9) |
| Sneezing | 7/12 (58.3) | 11/14 (78.6) | 15/22 (68.2) |
| Dyspnea | 7/12 (58.3) | 10/14 (71.4) | 14/22 (63.6) |
| Snoring/stertor | 7/12 (58.3) | 9/14 (64.3) | 12/22 (54.5) |
| Coughing | 2/12 (16.7) | 4/14 (28.6) | 6/22 (27.3) |
| Facial distortion | 4/12 (33.3) | 6/14 (42.9) | 10/22 (45.5) |
| Pain on manipulation | 2/12 (16.7) | 1/14 (7.1) | 3/22 |
| Ocular discharge | 5/12 (41.7) | 2/14 (14.3) | 6/22 (27.3) |
| Unilateral | 5/12 | 5/22 (22.7) | |
| Mandibular lymphadenomegaly | 3/12 (25) | 1/14 (7.1) | 4/22 (18.2) |
| Unilateral | 3/12 | 3/22 | |
| Systemic signs | 5/12 (41.7) | 6/14 (42.9) | 9/22 (40.9) |
| Lethargy | 3/12 (25) | 4/14 (28.6) | 7/22 (31.8) |
| Weight loss | 2/12 (16.7) | 4/14 (28.6) | 5/22 (22.7) |
| Anorexia | 3/12 (25) | 2/14 (14.3) | 4/22 (18.2) |
The first column considers only patients that had CT examination (alone or coupled to rhinoscopy), the second column considers only patients that had rhinoscopy (alone or coupled to CT), and the third column considers all the study group. Percentages are in brackets.
All 22 animals had respiratory symptoms and 21 (95.5%) had chronic nasal discharge. Ten (45.5%) animals showed facial distortion (Figures 1A, 1B). Six (27.3%) had ocular discharge (Figure 1B), which was unilateral in 5 cases (22.7%). Four patients (18.2%) had mandibular lymphadenopathy, which was unilateral in 3 cases. Nine of 22 animals (40.9%) showed systemic signs and none showed neurological signs or dysphagia.
Figure 1.
Facial distortion and epiphora in a cat with a high-grade large B-cell lymphoma. The cat was presented with chronic respiratory difficulties and chronic nasal discharge. Marked facial distortion (A, B, arrows) and bilateral ocular discharge (B, white arrowheads) were present.
Computed tomographic features (Table 3)
Table 3.
Computed tomography features
| Characteristics | Animals with CT (n = 12) (percentage) |
|---|---|
| Bone lysis | 11/12 (91.7) |
| Turbinates | 10/12 (83.3) |
| Unilateral | 8/12 (66.7) |
| Paranasal bones | 9/12 (75) |
| Vomer bone | 6/12 (50) |
| Septum | 2/12 (16.7) |
| Cribriform plate, brain invasion | 1/12 (8.3) |
| Nasal mass-like effect | 11/12 (91.7) |
| Heterogeneous enhancement | 9/12 (75) |
| Homogeneous enhancement | 2/12 (16.7) |
| Moderate contrast uptake | 7/12 (58.3) |
| Marked contrast uptake | 4/12 (33.3) |
| Sinuses soft tissue attenuation | 11/12 (91.7) |
| Non enhancing — sinusal fluid | 10/12 (83.3) |
| Mildly enhancing — sinusal mass | 1/12 (8.3) |
| Soft tissue attenuation of extra-nasal structures | 10/12 (83.3) |
| Nasopharynx | 9/12a (72.2) |
| Retrobulbar | 4/12 (33.3) |
| Maxillary recesses | 2/12 (16.7) |
| Tympanic bullae | 1/12 (8.3) |
| Mandibular lymph node enlargement and heterogeneous enhancement | 1/12 (8.3) |
One cat had only a nasopharyngeal mass without any bony or nasal cavity involvement.
Nasal CT was performed in 9 dogs and 3 cats. Bone lysis was observed in 11 cases (91.7%). Turbinate destruction was seen in 10 animals (83.3%). The paranasal bones were eroded in 9 animals (75%). In 1 of them the cribriform plate was eroded with evidence of brain parenchyma invasion (Figure 2B).
Figure 2.
Post-contrast transverse CT scans at the level of the frontal sinuses and olfactory lobes of a dog with nasal adenocarcinoma (A) progressing cranially (B). Fluid accumulation in the left frontal sinus is apparent (A, B, *). Soft tissue attenuating material with extension to left sphenoid sinus and rostral left brain, with lysis of the calvarium (B, arrow) and cribiform plate (not depicted).
A nasal mass effect was observed in 11/12 cases, which were all enhanced after contrast medium administration, heterogeneously in 9 cases and homogeneously in 2. Eight of these 11 cases had nasopharyngeal extension (72.7%) and 4 had retrobulbar extension (36.4%). Only 2 of these had exophthalmia at physical examination. One cat had a nasopharyngeal mass effect, without any bony or nasal cavity involvement. For the 11 animals with bony lysis and nasal mass effect, the lesions were unilateral in 7 animals (63.6%).
Abnormal soft tissue attenuation of the sinuses was present in 11 patients (91.7%) (Figures 2A, 2B). Of these, 10 were non-enhancing, consistent with mucus buildup secondary to obstruction by the nasal mass, or sinusitis. Only 1 patient had a mildly enhancing sinus soft-tissue lesion, consistent with a sinusal mass.
Mandibular and retropharyngeal lymph nodes were assessed for each patient. Features were suggestive of metastatic spread in 1 case in which the right mandibular lymph node was enlarged, associated with heterogeneous and rim enhancement. Spread of the nasal sarcoma was diagnosed after cytological examination of fine-needle aspirate of this lymph node.
Examination by CT resulted in the classification highly suggestive of a tumor in 6 cases and consistent with a tumor in 5 cases (Table 1). There was no evidence of tumor in 1 case, in which CT revealed a well-circumscribed soft tissue attenuating mass in the nasopharynx without any involvement of the surrounding structures, which was suggestive of a polyp. Nasal tumor was therefore considered as the primary differential diagnosis in 11 of the 12 patients (91.7%) examined by CT. The CT 95% confidence interval was 61.5% to 99.8%.
A final diagnosis of nasal neoplasm was obtained by CT-guided FNA of the nasal lesion (n = 4), surgical biopsy (n = 2), subsequent endoscopy-guided biopsy (n = 2), blind biopsy with rhinoscopic biopsy forceps (n = 2), postmortem examination (n = 1), or FNA of the mandibular lymph node (n = 1). Nine of 12 patients were diagnosed with nasal carcinoma (2 adenocarcinomas, 2 neuro-endocrinal carcinomas, 1 each transitional carcinoma, anaplastic carcinoma, and carcinoma of undetermined type), 2 with nasal sarcoma and 1 with nasal B-cell lymphoma.
Rhinoscopic features (Table 4)
Table 4.
Rhinoscopic features
| Characteristics | Animals with rhinoscopy (n = 14) (percentage) |
|---|---|
| Abnormal nasal mucosa | 14/14 (100) |
| Well-circumbscribed and mobile nasal mass | 6/14 (42.9) |
| Friable mass from choanae | 1/14 (7.1) |
| Diffuse rough proliferative aspect of mucosa | 7/14 (50) |
| Diffuse erosive appearance of nasal turbinates | 3/14 (21.4) |
| Mucosal hyperemia | 6/14 (42.9) |
| Exudates | 5/14 (35.7) |
Rhinoscopy was performed under general anesthesia in 11 dogs and 3 cats.
The nasal mucosa was abnormal in all cases, multiple abnormalities often reported in the same animal. The lesions were unilateral in 7 of 14 animals. The mucosa had a diffuse rough proliferative appearance in 7 patients (Figure 3A). A well-circumscribed and mobile mass was seen in 6 cases (42.9%) (Figures 3A, 3B). A non-lateralized friable mass protruding from the choanae was identified in 1 cat. The nasal turbinates in 3 patients showed a diffuse erosive appearance (21.4%). Protracted hemorrhage following biopsy was a complication in 1 dog and led to temporary insertion of a Foley catheter.
Figure 3.
Endoscopic image of pathological right side (A) and left side (B) of nasal cavities in 2 dogs with carcinoma-type epithelial tumors, both presented for bilateral nasal discharge with epistaxis. A well-circumscribed and mobile mass with rough proliferative mucosal aspect can be observed in the right part of the nasal cavity of the first dog (A, asterisk). A white mass extending from the cartilageneous junction of the nasal bone to the choanae is seen in the left side of the nasal cavity of the second dog (B, *).
Rhinoscopic examinations were highly suggestive of a tumor in 7 cases, consistent with a tumor (the primary differential diagnosis) in 2 cases, consistent with both a tumor and an inflammatory process in 1 case and there was no evidence of a tumor in 4 cases (Table 1). After endoscopy, nasal tumor was therefore considered as the primary differential diagnosis in 9 of the 14 patients (64.3%) examined. The endoscopy 95% confidence interval was 41.9% to 91.6%.
A final diagnosis of nasal neoplasm was obtained by endoscopy-guided biopsy (n = 11), surgical biopsy obtained during surgical excision of the nasal mass (n = 2, one of whom had also a previous diagnostic endoscopy-guided biopsy), or histology on nasal mass extracted by nasal flushing (n = 1). Thirteen of 14 patients were diagnosed with nasal carcinoma (7 adenocarcinomas, 4 transitional carcinomas, 1 each neuro-endocrinal carcinoma and carcinoma of undetermined type); and 1 with nasal sarcoma.
Among the 4 patients that had no endoscopic evidence of a nasal tumor, a traumatic foreign body was suspected to be responsible for inflammatory abnormalities of the mucosa in 1 case but CT images were highly suggestive of a nasal tumor. In another, rhinoscopy was consistent with a nasopharyngeal polyp, which was subsequently found to be neoplastic by histological assessment. In 2 other patients, endoscopic examinations resulted in chronic inflammatory processes as the main differential diagnosis, whereas nasal CT was highly suggestive of a tumor in 1 and not performed in the other.
Error frequencies of diagnostic conclusions stated after CT and rhinoscopy were not significantly different between the modalities for the 18 animals that had undergone only 1 diagnostic procedure (P = 0.48).
Three dogs and 1 cat underwent both procedures. In these cases, agreement between the modalities was observed in only 1 dog, both being highly suggestive of a nasal tumor. This patient was diagnosed with nasal carcinoma of undetermined type via endoscopy-guided biopsy. Diagnostic conclusions were different for the 3 other cases. In 2 dogs, CT was consistent with a tumor, whereas there was no rhinoscopic evidence of a tumor. Surgical biopsies concluded nasal adenocarcinoma and neuro-endocrinal carcinoma, respectively. In the cat, endoscopy was highly suggestive of a tumor, whereas CT suggested a nasopharyngeal polyp. Endoscopy-guided biopsy showed there was a nasal adenocarcinoma.
Discussion
This study focused on dogs and cats with cytologically or histologically confirmed nasal neoplasm. All but one had chronic nasal discharge that was mostly unilateral and hemorrhagic. Chronic sneezing, dyspnea, and stertor were also common findings, in accordance with the literature (3,7). Almost half the study group had facial distortion, a feature reported to be uncommon in dogs with nasal neoplasia (7). This could be due to the tumors in our study being more advanced than those in this previous report.
Computed tomography contributed to a nasal tumor being considered as the primary differential diagnosis in 11/12 patients. This procedure therefore appeared very reliable to reinforce a clinical suspicion of nasal neoplasia. A nasal mass-effect, regional bony lysis and soft tissue attenuation of the sinuses were strong indicators of nasal neoplasia, each encountered in 11/12 (91.7%) cases. Similarly, a previous study described a nasal mass effect in 17/19 (89.5%) dogs with a nasal tumor (6) and the literature indicates that bone lysis and soft tissue attenuation of the sinuses are strong predictive indicators of nasal tumors (3,6,7,14). Computed tomographic findings of extension to the nasopharynx were frequently observed (8/12, 67% of patients) as previously reported (3,7). Only 1 patient in our study had cribriform plate erosion although this feature has been reported in 40% of cats and 42% to 46% of dogs with nasal tumors (3,6,7). This discrepancy cannot be explained by potentially having earlier stages of tumor development in our study group, because the high rate of facial distortion would suggest the opposite. Cribriform plate disruption also depends on the epicentre of the nasal neoplasm, and the tumors in our study group may have been more rostrally located than in previous studies. Another possible explanation is that the inclusion criteria required pathological diagnosis, so it is possible that patients with cribriform plate lysis by a mass were not sampled because CT features were considered pathognomonic of a neoplasm.
Images consistent with metastatic spread are valuable to reinforce the presumptive diagnosis of a tumor, but these were encountered in only 1 of 12 dogs in this study. For this dog, fine-needle aspiration confirmed metastatic spread of a nasal sarcoma in mandibular lymph nodes.
The only false negative CT result was observed in a cat. In this case, a non-enhancing, minimally destructive adenocarcinoma was mistaken for a nasopharyngeal polyp, whereas the rhinoscopic appearance was in favor of a tumor. Another study reported 2 cats with choanal masses diagnosed by rhinoscopy with an apparently normal nasopharyngeal lumen on CT (3). The authors suggested that the nasopharyngeal masses were not completely surrounded by air and therefore could not be differentiated from surrounding tissue within the nasal cavity on CT images.
Nasal tumor was the primary differential diagnosis in 9 of 14 (64.3%) patients which underwent rhinoscopy. Observing a mass-like lesion during rhinoscopy is generally considered highly suggestive of a nasal tumor (3,4,7). Such an observation was made in half the study group, either in the nasal cavity (6/14, 42.9%) or protruding from the choanae (1/14, 7.1%). Other common rhinoscopic findings such as rough proliferative aspect (7/14) or diffuse erosive appearance (3/14, 21.4%) of the nasal mucosa were less specific observations. An inflammatory process was considered more probable than a neoplastic infiltration in 4/14 (28.6%) animals subsequently classified as false negatives. The fifth false negative was attributed to a cat with a choanal mass judged consistent with a nasopharyngeal polyp during rhinoscopy, but categorized as neoplastic by histopathology.
The rate of suspicion of a nasal tumor as the primary differential diagnosis was lower following rhinoscopy (9/14, 64.3%) than CT (11/12, 91.7%). The difference did not reach statistical significance, but CT tended to be more reliable than rhinoscopy for detecting nasal tumors, which is consistent with previous reports (3,6,7). This finding should be interpreted with caution because of the small size of the study group, the heterogeneity of the sample population and the diversity of neoplasia types. The greater diagnostic adequacy of CT could also have been overestimated due to possible bias when deciding which first-line procedure to use. Computed tomography might have been preferred over rhinoscopy when there was a stronger suspicion of neoplasia, and thus in the most advanced cases. The selection of cases in this study required a final diagnosis of nasal neoplasia that was histologically or cytologically confirmed. It was therefore possible to establish the false negative rates associated with CT and/or endoscopy with certainty. However, it impeded establishing the false positive rates of both modalities since this would have required the inclusion of all cases of nasal disease with a confirmed etiology.
For both CT and endoscopy, the most likely diagnosis was based on an independent review of in-depth reports, static images, and the conclusions from the original report. Conclusions from the report could have influenced experimenters, but interpreting only retrospectively static images would have introduced a bias. Either one radiologist or 2 internists, all experienced operators, performed the original examinations, so the original reports could be considered reliable and uniform. There was also a strong agreement between the level of suspicion provided by objective CT and rhinoscopic criteria defined in the materials and methods and the original overall conclusions, so that a source of bias appeared improbable.
Only 4 animals underwent both CT and endoscopy, which is the major limitation of our study. Ideally, both procedures should have been performed in each patient to allow a direct systematic comparison of diagnostic adequacy of both modalities. This limitation is due to the retrospective nature of the study and financial constraints of owners that impeded complete investigations for most cases. However in the 4 cases for which both procedures were implemented, CT again appeared more reliable than rhinoscopy for identifying nasal neoplasia.
These 4 cases were not included in the statistical analysis because Fisher’s test can only be applied to unpaired populations. Potentially the difference in error frequency might have changed, but the impact is probably negligible considering the small number of animals that had both procedures.
The most significant factor making rhinoscopy less reliable than CT for the diagnosis of nasal tumors is probably the presence of exudates and hemorrhage, produced by the tumor or the procedure, that can impede complete and accurate rhinoscopic examination (4,14). Protracted hemorrhage after biopsy was a complication in only 1 case in our study, consistent with a previous report in which only 2% of the population had this complication (4). Rhinoscopy can also be frustrating in cats which have a small nasal cavity relative to the size of the insertion tube of the endoscope.
One clear advantage of endoscopy over CT is that it allows visualization for non-surgical minimally invasive biopsies. Therefore, rhinoscopy may still be the better diagnostic test for nasal neoplasia. However, our study cannot address the comparative reliability of endoscopy-guided biopsy versus blind or CT-guided biopsy, as inclusion criteria excluded cases for which endoscopic biopsies sampled non diagnostic peritumoral tissue.
In patients with facial distortion, a blinded biopsy procedure only, without further examination, could have been justified to reduce expenses for owners who do not wish to pursue treatment.
The results of this study highlight the complementary nature of CT and endoscopy when dealing with a suspicion of a nasal tumor. Both examinations should be performed whenever possible, although our findings appear to indicate that CT is the better first-line procedure when a choice has to be made. Endoscopy is useful for providing additional information in cases with equivocal CT features, normal CT features with a strong suspicion of nasal tumor and for performing biopsies under visual control. However, definitive diagnosis still requires histopathological or cytological analyses.
Further work would involve a larger prospective study systematically coupling CT and endoscopy, studying dogs and cats separately, and ideally distinguishing between tumor types.
Acknowledgments
The authors thank Ms. M. L. Delignette-Muller for her help in statistical analysis and Dr. A. King for her assistance in reviewing the manuscript. CVJ
Footnotes
Use of this article is limited to a single copy for personal study. Anyone interested in obtaining reprints should contact the CVMA office (hbroughton@cvma-acmv.org) for additional copies or permission to use this material elsewhere.
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