Collision Tumour Comprising Desmoplastic Ameloblastoma and Squamous Odontogenic Tumour in the Anterior Maxilla: A Case Report

Abstract

Collision tumours, characterized by the simultaneous occurrence of two distinct neoplasms within the same anatomical site, are exceedingly rare in oral pathology. This case report presents an uncommon collision tumour involving desmoplastic ameloblastoma and squamous odontogenic tumour in the anterior maxilla of a 52-year-old male from the Indian population. Desmoplastic ameloblastoma is a variant of ameloblastoma known for its unique histopathological features, while squamous odontogenic tumour is a benign epithelial odontogenic tumour with distinctive clinical behaviour. The rarity of this occurrence emphasizes the need for accurate diagnosis and effective treatment strategies. This report discusses the clinical presentation, radiographic findings, and histopathological characteristics of this collision tumour. Through the presentation of this case, we aim to contribute to the understanding of these rare entities and their management considerations.

Introduction

Collision tumours are exceedingly rare occurrences in the field of oral and maxillofacial pathology, characterized by the presence of two distinct neoplasms within the same anatomical location. Desmoplastic ameloblastoma (DA) and squamous odontogenic tumour (SOT) are both uncommon odontogenic tumours, each possessing distinct histopathological and clinical features. Desmoplastic ameloblastoma is a variant of ameloblastoma with unique histological characteristics, while squamous odontogenic tumour is a benign neoplasm of epithelial odontogenic origin. Herein, we present a case report of a 52-year-old male from the Indian population who presented with a collision tumour composed of desmoplastic ameloblastoma and squamous odontogenic tumour in the anterior maxilla. This case not only highlights the rarity of such an occurrence but also underscores the importance of accurate diagnosis and appropriate management strategies for these intriguing entities. In this report, we discuss the clinical, radiographic, and histopathological aspects of this unusual collision tumour, providing valuable insights for clinicians and pathologists encountering similar cases.

Case Report

52 years old Indian male presented with a painless swelling that started appearing 6 months earlier in the right side of his upper jaw; slow growing and seemingly asymptomatic, until recently the adjacent teeth became misaligned, mobile, and tender on vertical percussion.

On further intraoral inspection and palpation, the bony hard swelling was measured approximately 2.5 × 2 cm in the right anterior maxillary region, involving primarily the alveolus and encroaching the gingivobuccal sulcus (Fig. 1).

Fig. 1.

Bony hard swelling the right anterior maxillary region

Facial asymmetry was noted, with diffuse swelling in the right upper lip region, obliterating the right nasolabial fold and elevating right ala of nose (Fig. 2).

Fig. 2.

Facial asymmetry present

Digital orthopantomogram revealed an ill-defined mixed area of radiopacity and radiolucency, involving the alveolus from 11 to 13 with significant displacement of roots of the teeth. An impacted supernumerary tooth was also noted in the region (Fig. 3).

Fig. 3.

Digital orthopantomogram

In the axial section of CT scans, a well-demarcated area of radiolucency with coarse dense septa noted in the right anterior maxilla, with the buccal cortical plate expanded significantly as compared with the palatal cortex being uninvolved (Fig. 4).

Fig. 4.

Axial section of CT scan

Patient's medical history was unremarkable other than hypertension for which he is under medication. Incisional biopsy was performed and the sections stained with haematoxylin–eosin revealed the presence of numerous irregular islands of neoplastic, well-differentiated squamous epithelium dispersed in the abundantly dense fibrous connective tissue stroma having moderate number of plump, spindle shaped fibroblasts, multiple trabeculae of woven bones and very few chronic inflammatory cells. Peripheral cells in the epithelial islands are not palisaded and rather flattened in shape. Epithelial islands often contain polygonal cells with hyperchromatic nuclei. Polygonal epithelial cells are eosinophilic with centrally placed nuclei and possess well-defined intercellular junctions. This histopathology was suggestive of Squamous Odontogenic Tumour (SOT) (Fig. 5A, B).

Fig. 5.

a, b Photomicrographs (10×, H and E stain) showing presence of irregular neoplastic odontogenic epithelial islands having peripherally placed flattened epithelial cells and centrally placed squamous epithelium with distinct intracellular bridges within densely packed stroma

Following the diagnosis from incisional histopathology, a partial maxillectomy was planned under general anaesthesia to excise the lesion with 1 cm safe margins. Overlying mucosa was sacrificed and sampled with the final specimen. Surgical defect was closed primarily (Fig. 6).

Fig. 6.

Excision with 1 cm safe margin

Post-operative gross specimen was completely processed and evaluated keeping in mind the previous histopathological features. Surprisingly, the sections stained with conventional haematoxylin and eosin revealed numerous neoplastic odontogenic epithelial follicles and islands composed of peripherally arranged tall-columnar ameloblast like cells with reverse nuclear polarity encasing inner mass of stellate reticulum like cells. Stroma was densely fibrous or desmoplastic (Fig. 7A, B).

Fig. 7.

a, b Photomicrographs (a 10×, H and E stain) showing presence of ameloblastoma like follicles with tall-columner ameloblast like cells with reverse nuclear polarity and central zone of stellet reticulum like cells with desmoplastic connective tissue stroma and (b 10×, H and E stain) concomitant presence of sot like squamous epithelial islands

This was suggestive of Desmoplastic Ameloblastoma (DA) in association with SOT.

Discussion

Desmoplastic ameloblastoma remains to be one of nature's secrets due to the dearth of case series. It was first described by Eversole et al. who labelled it as an “ameloblastoma with pronounced desmoplasia or DA” [1]. In 2005, WHO (World Health Organization) classified it as a variant of ameloblastoma with typical clinical, imaging and histological features [2]. But in 2017, it was considered as one of the histological variants of conventional ameloblastoma. [3]

Desmoplastic ameloblastoma (DA) constitutes 0.9% to 12.1% of all ameloblastomas [4]. The age distribution of DA is 3rd to 5th decades of life with a mean age of 41.9 years (range 17–70 years). Usually there is equal gender distribution, but some reports suggest male preponderance [1, 5]. Data from different geographical regions seem to suggest a bio-geographical pattern in that the relative frequency of DA is slightly higher in Asian population. [6]

The anterior premolar area of the jaws is typically affected by DA, with equal incidence in the mandible and maxilla [7, 8]. This is in contrast to the traditional ameloblastomas which typically develop in the mandibular posterior region [9]. Due to its prevalence in maxilla it is much more challenging. Firstly, because of the thin cortical plates of maxilla the lesion easily enters the maxillary sinus and grows rapidly as there is no physical barrier [12]. Secondly, the proximity of important anatomical structures like pterygopalatine fossa and orbit makes its clearance difficult [13]. In our case, the patient was a 52-year-old male patient with the lesion involving the right anterior maxilla region.

It is thought that periodontal membrane of the associated tooth is the main cause why desmoplastic ameloblastoma occurs. Moreover, some contend that epithelial rests of Malassez may be the cause of desmoplastic ameloblastoma [10].

DA’s are usually presented as a painless, swelling of the tooth bearing areas of the jaws [8]. There is buccal cortical plate expansion with tooth displacement in almost 92% of the cases and root resorption in 33% of cases [11]. The size of the tumour varies between 1.0 and 8.5 cm in diameter [14]. The patient in this case report had a slow enlarging painless growth of approximately 2.5 × 2.0 cm with buccal expansion and displacement of the teeth.

Radiologically DA’s are usually present as mixed radiolucent/radiopaque lesion with calcified foci at the periphery in 64% of cases, whereas radiolucent in 36%. The osseous metaplasia within the thick fibrous septa gives a mixed a mixed radiograph picture rather than mineralized product of tumor. [8]

Reichart et al. in their study found that 51% of the tumours were unilocular and rest were multilocular [15], but Effiom and Odukoya stated that multilocular radiolucency is the predominant radiographic presentation of the desmoplastic ameloblastoma. [16]

According to B.R Chrcanovic et al. 70% of the DA’s are ill-defined, without capsule, suggestive of an infiltrative process. Thompson et al. [21], stated that the resorption of the normal lamellar bone trabeculae at the periphery of this lesion is probably caused by tumour expansion, and the production of new bone around these resorbed trabeculae represents an attempt to repair the damage caused by tumour expansion. This, and the infiltration of the collagenous tumour stroma between these trabeculae, could account for the in-distinct borders seen on conventional radiographs [17]. Bone expansion with tooth displacement and knife-edge resorption of the roots of the involved teeth are also appreciated in radiology [19]. Radiologically DA’s mimic fibro osseous lesions, odontogenic myxoma, chronic sclerosing osteomyelitis, ameloblastic fibroma and if well-circumscribed, an ossifying fibroma [17]. A characteristic CBCT feature of DA is the honeycomb-like appearance formed by coarse trabecular septa [18]. In our case report, there was unilocular radiolucency with buccal plate expansion and coarse dense septa. Resorption of the roots and loss of periodontal space was also appreciated.

Histopathology is necessary for a conclusive diagnosis before surgery for proper treatment. DA’s are potentially aggressive due to 1) potential to grow to a large size; 2) the common location in the maxilla leading to an early invasion of adjacent structures; 3) the diffuse radiographic appearance, and 4) histologic finding of bone invasion. [8]

Considering the infiltrative, ill-defined, non-capsulated nature of the lesion, simple curettage or enucleation is insufficent [16]. Therefore, block excision is the most widely accepted form of treatment [20]. Simple curettage leaves islands of tumour within the bone, which later manifest as recurrences. Keszler et al. reported a higher recurrence rate (21.4%) for desmoplastic variant than the other types (10.1%) of ameloblastoma [21].

Reasons for recurrence is the lack of reliable diagnosis before operation. Secondly, DA is frequently present with ill-defined border making the exact interface of the lesion with normal bone difficult to investigate. Lastly, its prevalence in maxilla may produce an early invasion of the adjacent structures [22].

Conclusion

Desmoplastic variant of ameloblastoma is a rare entity. As the clinical and radiological findings mimic other benign lesions a proper histological diagnosis is must before surgery. because of owing to the aggressiveness and ill-defined boundaries a surgical resection is the treatment of choice to lower the chances of recurrence.

Declarations

Conflict of interest

The authors have no conflicts of interest to declare. All co-authors have seen and agree with the contents of the manuscript and there is no financial interest to report. We certify that the submission is original work and is not under review at any other publication.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed consent

Informed consent was obtained from all individual participants included in the study.