Abstract
Oncocytomas are unusual neoplasms of the head and neck that occur mainly in the parotid gland. The authors report a case of bilateral submandibular gland oncocytoma in a patient with multiple endocrine neoplasia 2B syndrome and neurofibromatosis type 1. Histopathology of the resection specimens demonstrated lymphovascular invasion but no other aggressive features. This was a highly unusual feature in an otherwise rare benign tumour.
Oncocytes are large epithelial cells with an eosinophilic granular cytoplasm containing many mitochondria. Within a background of oncocytosis, which is common in ageing salivary glands, a spectrum of rare neoplastic and non-neoplastic changes may occur.
These changes, thought to be due to acquired progressive mitochondrial dysfunction, include nodular oncocytic hyperplasia, oncocytic cystadenoma or oncocytoma, with or without myxoid change or metaplasia . Histopathological categorisation of these changes is often difficult . Rarer still are the sequelae of recurrence, local invasion or malignant neoplasms, such as malignant metastasising oncocytoma and oncocytic adenocarcinoma . Oncocytomas are rare benign monomorphic adenomas, accounting for 0.1–1.5% of all salivary gland tumours . They mainly affect the parotid gland and only 8–11% have been reported to originate in the submandibular gland.
There are no previous reports of true bilateral submandibular gland oncocytoma in the English literature. The authors present such a case, in a patient with multiple endocrine neoplasia 2B (MEN2B) syndrome and neurofibromatosis type 1 (NF1).
Case report
A 61-year-old Caucasian woman with MEN2B syndrome and NF1, under review for nodular thyroid disease was found to have bilateral submandibular gland masses on ultrasound as an incidental finding. On further questioning, the patient reported long-standing mild tenderness of both submandibular glands but no other salivary symptoms.
The patient had an extensive medical and surgical history, attributable to her MEN2B and NF1 conditions. This included subtotal colectomy with ileo-rectal anastamosis for obstruction due to ganglioneuromas, colorectal polyposis, somatostatinoma of ampulla of Vater, benign nodular thyroid disease diagnosed radiologically with no thyroid removed, right phaeochromocytoma with adrenectomy, and multiple excisions of neurofibromata. She had received no previous head and neck radiotherapy.
On examination there was mild diffuse enlargement of both submandibular glands on bimanual palpation, the left was larger than the right, both were slightly tender. Otherwise the examination was unremarkable with normal secretion of saliva intra-orally. The patient had multiple 1–2 cm diameter cutaneous neurofibromata on her trunk and a probable basal cell carcinoma (BCC) on her left cheek.
Computerised tomography (CT) with contrast of the soft tissues of the head and neck demonstrated homogenously enhancing nodules within both submandibular glands, and the patient was subsequently referred to the department of oral and maxillofacial surgery. Figure 1 is the coronal view of the right and left submandibular glands.
A provisional differential diagnosis of pleomorphic adenoma or metastases from her previous somatostatinoma was made, but ultrasound-guided fine needle aspiration cytology (FNAC) from the left gland confirmed bilateral oncocytoma. A decision was made to excise both submandibular glands electively.
The submandibular glands were both excised under a single general anaesthetic using a standard submandibular approach with a sub-capsular dissection to preserve the marginal branch of the facial nerve. At operation, the masses gave the impression of being firm, lobulated and well encapsulated within the glands, which were only mildly enlarged. The BCC was simultaneously excised from the patient’s left cheek and closed primarily.
The patient made an uneventful recovery with no marginal mandibular nerve compromise. At 1 year review, there has been no evidence of recurrence.
Histopathology
The glands were fixed in 10% formal saline, routinely processed and stained with haematoxylin and eosin (HE). The macroscopic appearance of the specimen demonstrated well-circumscribed brown masses, bilaterally encapsulated within fibrous tissue within the submandibular gland parenchyma, which was bilaterally pale in appearance.
Microscopic examination revealed, in the left submandibular gland, a well-demarcated and encapsulated tumour forming nodules and acinar structures with intervening fibrosis and calcification in the stroma ( Fig. 2 ). It was excised with clear margins.
The tumour cells had mildly enlarged nuclei with no significant pleomorphism, central prominent nucleoli and abundant granular eosinophilic cytoplasm ( Fig. 3 ). Mitoses were inconspicuous. There was no transcapsular, perineural or local invasion, but several foci of vascular invasion were identified, in which tumour deposits were present within one venule and surrounding lymphatics, as shown in Fig. 4 . The remaining parenchyma showed focal oncocytic metaplasia. Overall, the features were consistent with oncocytoma. The tumour was negative for thyroid transcription factor, thyroglobulin, synaptophysin, CD56 and somatostatin, thus ruling out neuroendocrine tumours, which may appear oncocytoid or have mixed oncocytic features .
