Malignant Transformation of a Benign Oncocytoma of the Submandibular Gland: A Case Report

Abstract

Oncocytic carcinoma arising in the submandibular gland is an extremely rare tumor and only 11 cases have been reported previously. We report on a 51-year-old man with a previously benign oncocytoma in the submandibular gland that transformed from a benign morphology to malignant cellular atypia and mitosis. To our knowledge, the current report is the first published case of a malignant transformation from benign oncocytoma to oncocytic carcinoma of the submandibular gland. The proliferative activity of the tumor cells was evaluated immunohistochemically using antibodies against Ki-67.

Cytopathology approach to rare salivary gland lesions with oncocytic features

“…This explains why oncocytes in general and oncocytomas in particular are observed most frequently in patients above the age of 50 . Oncocytomas mostly occur in the parotid gland; however, cases of submandibular gland and minor salivary gland involvement have been reported as well . They are thought to arise from reserve cells in the intercalated ducts of the salivary glands, and possess an extremely low malignant potential, with rare reports of recurrence, malignant transformation, local invasion, or metastasis .…”

“…26,29,30 Oncocytomas mostly occur in the parotid gland; however, cases of submandibular gland and minor salivary gland involvement have been reported as well. [29][30][31] They are thought to arise from reserve cells in the intercalated ducts of the salivary glands, 32 and possess an extremely low malignant potential, with rare reports of recurrence, malignant transformation, local invasion, or metastasis. 28,33 Cases arising from the submandibular gland have not been found to recur after surgery, 28 suggesting that submandibular oncocytomas have a favorable prognosis.…”

Oncocytoma of the Submandibular Gland: Diagnosis and Treatment Based on Clinicopathology

“…Oncocytomas of the salivary gland are rare benign neoplasms that comprise 3-4% of head and neck tumors [ 5 , 20 ]. The majority of salivary gland tumors arise in the parotid gland (70%), followed by minor salivary glands (22%) and submandibular glands (8%) [ 5 ]. Submandibular oncocytoma is a very rare benign tumor that arises primarily in older Caucasian individuals aged 50–70 years.…”

“…In 33 cases to date, only one reported malignant differentiation from a benign lesion [ 23 ]. Characteristics of malignant transformation include local invasion into muscular, perineural, and lymphatic structures as well as microscopic features including nuclear atypia, cellular polymorphism, mitoses, and focal necrosis [ 5 ].…”

“…Oncocytomas are rare benign neoplasms composed of oncocytes or polyhedral cells with eosinophilic cytoplasm made up of abundant mitochondria and dark centrally located nuclei [ 1 – 3 ]. Hürthle first described oncocytes in a canine thyroid gland in 1894 [ 4 , 5 ]. The term “oncocytoma” was first used by Schaefer to describe “granular swollen cells” in ducts and acini of salivary glands [ 1 , 6 ].…”