Synchronous pleomorphic adenoma in the infratemporal fossa and contralateral submandibular gland and endoscopic removal

Abstract

The objective of this article is to elucidate on our experience with the first case reported in the literature of a synchronous presentation of pleomorphic adenoma (PA) in infratemporal fossa as well as the contralateral submandibular gland. PA most commonly arises from the major salivary glands but has also been reported to arise from minor salivary glands in unusual sites such as the nasal septum, main stem bronchus, trachea, lacrimal gland, external auditory canal, etc. However, it seldom involves the infratemporal fossa and extremely few cases are reported in the literature and coexistent contralateral synchronous PA is nowhere reported in literature. The infratemporal fossa tumour posed a diagnostic dilemma and therapeutic challenge because of its concealed location which we dealt successfully with endoscopic sublabial trans maxillary approach.

Background

The infratemporal fossa is a rare site for tumours and its anatomic location makes them to remain asymptomatic and undiagnosed for a long time. Some of the common tumours involving the infratemporal fossa are nasopharyngeal carcinoma, adenoid cystic carcinoma and juvenile angiofibroma.¹ Salivary gland tumours represent 3% of all head and neck tumours. Only 6% of the pleomorphic adenoma (PA) arise from the minor salivary glands mainly in the palatal mucosa of oral cavity.² They are also found infrequently in the nasal cavity, pharynx, larynx, trachea and lacrimal glands.³ Infratemporal space is an extremely rare location for PA, and only two cases have been reported in the English literature so far.^{1 3} One case of carcinoma ex PA is also reported to arise from infratemporal fossa.⁴ We describe a remarkable lesion in the infratemporal fossa with the first report of synchronous occurrence of PA in contralateral submandibular gland.

Case presentation

A 34-year-old man was admitted to our hospital complaining of swelling in the left side of his face for 3 months associated with on and off dull aching pain. There was a diffuse swelling in the left cheek. A small mucosal elevation was noted in the left retromolar trigone and a biopsy taken from that was suggestive of PA (figure 1). There was also a 2×2 cm firm nodular swelling palpable in the right submandibular region which the patient was ignorant before our examination. Fine-needle aspiration cytology from that neck swelling was suggestive of benign salivary neoplasm.

Figure 1.

Left retromolar lesion.

Investigations

CT was performed and showed a hypodense lesion measuring 5×3 cm in the left infratemporal fossa (figure 2A). The lesion was close to the ramus of mandible and the lateral pterygoid muscles and was causing anterior bowing of posterolateral wall of maxilla. There was no destruction or erosion of the adjacent bone. MRI with contrast was also performed which revealed the heterogeneous non-enhancing soft-tissue mass in the left infratemporal fossa along with a well-defined lesion in right submandibular gland suggestive of PA (figure 2B).

Figure 2.

(A) Axial contrast-enhanced CT shows a well-demarcated mass in left Infratemporal fossa (star) with anterior bowing of posterolateral wall of maxilla (arrow). (B) Coronal T1-weighted image shows the left infratemporal mass (star) along with a well-circumscribed mass in right submandibular gland (arrow).

Differential diagnosis

Not relevant as this is first such case being reported.

Treatment

Surgical excision was planned. Left sublabial incision was made in superior gingival periosteum of maxilla. It was elevated and anterolateral and posterolateral wall of the maxilla was exposed. Using endoscope, the tumour was traced from the left retromolar trigone into the left infratemporal fossa. Posterolateral wall of maxilla was drilled out for access into the infratemporal fossa hugging the lateral wall (figure 3A, B). The tumour was delineated from all its surroundings and removed en bloc. In the same sitting, a skin crease incision was placed in the right side of neck and submandibular gland excision was done and both the specimens (figure 4A, B) were sent for histopathological examination which were reported as PA.

Figure 3.

(A) The posterolateral wall of maxilla (arrow) drilled out under endoscopic view to access Infratemporal fossa tumour (star). (B) The mass is delivered via sublabial transmaxillary approach.

Figure 4.

(A) Infratemporal fossa specimen. (B) Submandibular gland specimen.

Outcome and follow-up

The immediate postoperative period was uneventful. The patient was given nasogastric tube feeds and was started with oral feeds from seventh postoperative day and discharged from the hospital and was kept on routine follow-up every year. He is symptom free for 2 years

Discussion

Salivary gland tumours represent 3% of all head and neck tumours.² Minor salivary gland tumours account for 22% of all salivary gland neoplasms with only 18% of them being benign.⁵ The PA is the most common benign major salivary gland neoplasm, accounting for 85% of all salivary gland tumours. They also account for 40%–70% of benign minor salivary gland tumours which are found infrequently in the nasal cavity, pharynx, larynx, trachea and lacrimal glands.⁶ They may arise along the cheek, along the Stenson’s duct and in accessory parotid tissue independent from the body of the gland,⁷ in the parapharyngeal space arising either de novo or from the deep lobe of the parotid gland and continuing through the stylomandibular tunnel into the parapharyngeal space.⁸ They can even develop in salivary gland inclusions within the lymph nodes in the neck.⁷ Its occurrence from the infratemporal fossa is extremely rare and only a few cases are reported in the literature.^{1 3 6}

Synchronous occurrence of multiple salivary gland tumours is extremely uncommon. PAs have been reported as occurring synchronously and metachronously within major salivary glands, but synchronous occurence of PA in a major salivary gland such as submandibular gland and minor salivary gland in infratemporal fossa has never been reported before. After an extensive PubMed search, we could come across only a single reported case in the international literature of a metachronous mixed tumour of bilateral parotid and submaxillary gland but not involving any minor salivary gland sites. This case report is the first in the English language literature where a synchronous PA is found in Infratemporal fossa and contralateral submandibular gland. The most likely aetiological factor associated with the development of two PAs in different sites is the irradiation delivered to the head and neck region in childhood.⁹ Interestingly, our patient did not have any history of exposure to radiation.

The clinical presentations of infratemporal fossa tumours are usually delayed as these tumours remain silent for a long time. A bulge in superior gingivobuccal sulcus has been reported to be the frequent initial manifestation of tumour.^{1 10} Our patient presented with a swelling in the left maxillary region as well as a bulge in the superior gingivobuccal sulcus near the retro molar trigone.

Imaging plays a vital role in assessment of an Infratemporal fossa lesions. CT scan with contrast enhancement helps to determine the extent of disease, local spread and also type of tumour.¹¹ MRI with contrast can lucidly evaluate the soft tissues involvement, intracranial extension also can suggest the origin of the tumour, but this is arduous in large tumours and those with multiple extensions.¹² MRI angiography or conventional arteriography may help to rule out a suspected vascular tumour.¹¹

The histopathology of both the specimens in our case confirmed PA. The probability of a superficial lobe tumour invading through the mandibular notch into this region was ruled out by imaging and surgical details. Though the deep lobe of the parotid gland and the infratemporal fossa are anatomically close structures, the possibility of deep lobe tumours spreading to the infratemporal fossa seems to be rare. Also, the extension from deep lobe of parotid tumours is distinguishable from de novo lesion in the infratemporal region by a fine lucent line depicting the compressed layer of fibroadipose tissue between the tumour and deep lobe of parotid.¹³ These findings were all corroborated in our case which indicated that the tumour was probably from ectopic minor salivary gland within the infratemporal fossa.

Numerous surgical approaches to the infratemporal fossa have been described such as lateral preauricular and postauricular approaches, anterior transmaxillary and inferior transmandibular approaches.¹⁴ Anterior surgical approaches to the infratemporal fossa include the sublabial transmaxillary approach, maxillary swing, Le Fort osteotomies and facial translocation.¹² Jeyanthi et al¹ used the lateral approach to manage the first reported case of infratemporal fossa PA and they accessed the infratemporal fossa via a zygomatic arch access osteotomy and coronoidotomy. A hemicoronal incision with preauricular extension was used to expose the zygomatic arch and a Weber-Fergusson incision was used to expose the intraoral part of the tumour.

Endoscopic endonasal transpterygoid approaches have been described to access the lateral recess of the sphenoid sinus and was then expanded to manage lesions of the middle cranial fossa and infratemporal fossa1.^15–17 Youssef et al¹⁸ considered endoscopic endonasal transpterygoid approach to be one of the most effective surgical solutions for most of benign and some malignant tumours that involve the infratemporal fossa and middle cranial fossa after their study on cadavers.

Anterior antrostomy, well known as the Caldwell- Luc approach, was named after American and French surgeons who independently described the sublabial approach to the maxillary antrum through the canine fossa. Although it is out of routine Ear Nose and Throat practice for treatment of Maxillary sinusitis, Gurey et al³ found it suitable for dealing with Infratemporal fossa tumour and they performed a typical anterior antrostomy and continued their dissection using endoscope through the posterolateral wall of the maxillary sinus in order to enter the infratemporal fossa and excise the tumour. Tanrivermis Sayit et al⁴ were also able to remove a Carcinoma ex PA from infratemporal fossa using the sublabial approach. We used the same approach in our patient as well and we were able to successfully manage the tumour by excising it en bloc. The advantages of this approach were manifold and noteworthy. It was a scar-less surgery with less morbidity to the patient, which led to faster recovery postoperatively. It also reduced the costs of treatment by decreasing the operation time to less than 45 min and also by decreasing the duration of hospital stay. However, as Kassam et al have postulated, scrupulous understanding of endoscopic anatomy of Infratemporal fossa with sharp skills in endoscope manoeuvrability are vital in avoiding surgery-related complications.¹⁹

The prognosis of a PA in both the reported cases was good. Because of its obscure location, follow-up of patient with only clinical monitoring may not be sufficient. Periodic radiological evaluation is recommended.

Learning points.

• The location of infratemporal fossa is extremely rare for pleomorphic adenoma.

• Synchronous occurrence of pleomorphic adenoma in contralateral major salivary gland is extraordinary.

• Management of the tumour using sublabial approach with endoscopic assistance gives less morbid, more precise and complete clearance under expert hands.