Chondrosarcoma in the Parapharyngeal Space; Site of Origin an Enigma

Abstract

Chondrosarcoma of the head and neck region is a rare disease, representing approximately 0.1% of all head and neck neoplasms. We present a case of a 30 year old male who presented with swelling in the right retroauricular region since 4 years. Magnetic resonance imaging and computed tomography showed lesion with its epicentre in the post styloid compartment of right parapharyngeal space with superior extent around the petrous apex. The surgical procedure considered was excision. Surgical excision was challenging in view of difficult surgical access due to close and intricate relation with neurovascular structures of head and neck and an unsual pattern of spread.

Introduction

Chondrosarcomas are a heterogeneous group of malignant tumors formed by tumor cells that produce cartilagenous matrix [1]. Chondrosarcoma of the head and neck region is a rare disease, representing approximately 0.1% of all head and neck neoplasms [2]. It commonly originates in the bones of the head and neck. It is an unusual neoplasm that is slow-growing and represents only 1–3% of all cases of chondrosarcoma [3]. The most common site of occurrence of these tumours in head and neck region is maxilla followed by mandible, nasal cavity, larynx, skull base and cervical vertebrae [4]. 66% of skull base chondrosarcomas occur within the Petrooccipital fissure [5]. Given their usually slow growth rate, they are capable of reaching sizable dimensions, promoting bone erosion, and significant displacement of neurovascular structures. Computed tomography (CT) and magnetic resonance imaging (MRI) are employed to evaluate the tumor on presentation. Calcification is present in approximately 50% of tumors, typically in rings and arcs [6]. MRI is useful to demonstrate the soft tissue extent of the tumor and to delineate the extent of the intraosseous and soft tissue involvement preoperatively [1, 7]. These tumors are primarily managed by surgical excision but achieving a clear margin is seldom possible. Though not responsive to radiation but can be considered in post surgical patients with minimal residual disease.

Case Report

1. 30 year old male patient presented with a swelling in post aural region for 4 years with a recent onset of pain for 2 months with no other functional or neurological deficits (Fig. 1a). General examination was grossly normal. Function of all cranial nerves were assessed and was found to be normal. Local examination revealed a 3 × 2.5 cm ovoid swelling present in the right post-auricular region, not warm, non tender, firm in consistency, fixed and immobile in all directions, with ill-defined antero-superior margin, smooth surface, non-compressible, non-pulsatile, overlying skin normal with no sinus/fistula. Computed Tomography of the neck revealed a large hypodense lesion measuring ~ 5 × 3.4 × 4.2 cm (ap × tr × cc) in size in the post styloid compartment of right Parapharyngeal space extending into paravertebral space with peripheral calcification. Superiorly it is reaching up to skull base causing bone changes in the form of erosion of occipital and mastoid bone, with expansion of the jugular fossa. The transverse process and foramen of the atlas however are well preserved and the image shown in Ib gives a false impression of destruction of transverse process of atlas as a result of partial volume averaging (Fig. 1b). Magnetic Resonance Imaging confirmed a T1 isointense/T2 hyperintense lesion in the similar location, anteriorly the lesion was closely abutting the deep lobe of right parotid gland with maintained fat planes, superiorly the lesion was reaching up to petrous occipital fissure (Fig. 1c). Fine needle aspiration cytology from the lesion revealed pleomorphic adenoma. In view of the unusual site, slides were reviewed and were consistent with pleomorphic adenoma. Patient was planned for surgical excision under general anaesthesia after proper informed consent. The standard infratemporal fossa Fisch approach was used with incision site marked as shown in Fig. 1a. After elevating the flaps, superficial parotidectomy was done. Mass was seen extending deep to the mastoid tip which was drilled for better exposure. Intra-operative findings revealed ~ 6 × 5 cm globular swelling in the right retroauricular region with extension into the post styloid compartment of right Parapharyngeal space, posteriorly extending in the paravertebral space till the transverse process of C1 vertebra and superiorly till the basiocciput (Fig. 2a). Facial nerve trunk and its branches were identified and preserved (Fig. 2b). Post-operatively patient developed marginal mandibular nerve paresis which improved subsequently. Functions of all other cranial nerves were intact post-operatively. Post-operative histopathology revealed lobules of moderately cellular tumour composed of closely packed chondrocytes having mild to moderate nuclear atypia (Fig. 2c). Stroma showed myxoid changes with focal calcification. Findings were consistent with Chondrosarcoma, Grade II. Immunohistochemistry was not performed. All of the 5 lymph nodes from level II were free of tumour. Post-operative MRI revealed minimal residual disease close to basi-occiput. The lesion was left behind as it was inaccessible. Post-operatively patient was subjected to adjuvant chemoradiation. He received conformational dose of 6600 cGy 6 weeks after surgery along with concomitant Cisplatin and Adriamycin based chemotherapy. He received 3 cycles of chemotherapy. Patient had severe nausea and vomiting after the first cycle which was medically managed. The patient is now under close follow-up post operatively and is doing well without signs and symptoms of any progression, and has recovered fairly well from chemoradiation associated morbidity.

Fig. 1.

a Surgical approach and incision. b Computed tomography showing origin and spread with classic rim-arc calcification. c Magnetic resonance image showing origin and pattern of spread

Fig. 2.

a Intra-operative delineation of mass and drilling of mastoid tip. b Facial nerve trunk and its anterior and posterior division. c Histopathological image of chondrocytes in myxoid background

Discussion

Our patient presented with a swelling in the right retroauricular region. Imaging analysis showed a heterogenous soft tissue density with peripheral calcification in the post styloid compartment of the right Parapharyngeal space with wideneing of petro-occipital fissure. It is hypothesised that the tumor originated at the level of Petro occipital suture line and extended inferiorly along the path of least resistance into the potential parapharyngeal space. Contrast Enhanced CT showed a clear demarcation between the tumor and the deep lobe of parotid.

The usual course of spread of any mass in the Parapharyngeal space is through the stylomandibular tunnel. However, in our case the mass has taken an unusual course by widening the paravertebral space between the mastoid tip and first cervical vertebra. So instead of presenting as a neck mass, patient presented with a retroauricular swelling. This presentation and pattern of spread is rarely encountered.

Another dilemma was that the pre-operative Fine needle aspiration cytology was pleomorphic adenoma and patient was planned for surgical excision. Intra-operatively we encountered a part of the lesion extending into the skull base in the region of petro-occipital complex. The tumor was removed completely from the parapharyngeal space, however at the probable the point of its origin near the petro occipital region a part of the tumour was left due lack of space for surgical manoeuvrability and risk of injury to neurovascular bundles. Additionally aggressive resection would have lead to post-operative morbidity for a benign pathology. Post operative histopathology however showed chondrosarcoma grade II. Previous FNA slides were re- reviewed due to discrepancy in the histopathology report, however it was again reported as pleomorphic adenoma and it was concluded that the probable site of aspiration may not have been appropriate.

Based on the radiology lateral skull base lesions (LSBTs) can be kept as differential diagnosis. Most LSBTs are benign (65–75%), and they usually originate from the salivary glands comprising 40–50% of the total. The rest are neurogenic (20%) or otherwise (20%) [8]. Manifestations of LSBTs include a mass in the oropharynx or the upper neck, changes in voice, cranial nerve deficits, and so forth. However, in some cases, LSBTs may go undetected for a long time, and they usually present as an asymptomatic mass [9]. A variety of surgical approaches have been described for management of LSBTs, the most common among them including the transmandibular, the transmaxillary, transparotid-transcervical and the transcervical approaches. The decisive factor that affects the option of the surgical approach is which one will maximize exposure for intact tumor excision while minimizing functional and aesthetic deficits.

Evans et al. [10] classified them in 3 degrees, from I to III histological grades. Though, the most common site of chondrosarcomas in the head and neck is the maxilla, there are a few case reports in literature suggesting its origin at the cranial base [4]. Skull base chondrosarcomas are usually low grade and have an indolent growth pattern. Chondrosarcoma is most common between the third and fourth decades of life [1]. Diagnosis is always a challenge because cartilaginous neoplasms have different histologic patterns, from benign chondroid tumors to malignant undifferentiated neoplasms. Identifying the exact site of origin is of utmost importance for adequate surgical excision and adjuvant therapy. The consensus is that surgical treatment is the most effective therapy for chondrosarcoma. Dissection of the cervical lymph node is not routinely performed due to a low incidence of lymph node metastases. Generally, radiation is performed for palliative cases, unresectable cases or as an adjunctive therapy in cases of residual disease, but not as an initial or single treatment. Chemotherapy has limited effect on chondrosarcoma. In high-grade mesenchymal chondrosarcoma cases with early local recurrence and aggressive behavior or potential metastasis, it can be employed as an adjuvant therapy. The main prognostic factors are surgical resection, stage, grade and primary site.

Conclusion

Identifying the site of origin of the lesion and its pattern of spread is of paramount importance in chondrosarcomas as maximal tumor resection with function preservation is the choice of surgical approach.

Funding

Nil.

Compliance with Ethical Standards

Conflict of interest

There are no potential conflicts of interest.

Informed Consent

An informed consent was obtained from the patient included in the study.