A case of pleomorphic adenoma of the submandibular gland with remarkable cystic formation

Abstract

Pleomorphic adenoma is the most frequent benign tumor derived from salivary glands. Usually, this tumor presents as a painless and solid mass. In this report, we describe an extremely rare case of pleomorphic adenoma of the submandibular gland with remarkable cystic formation. The patient was a female in her fifties who had a painless mass that had persisted for 20 years in the left submandibular region. CT and MRI revealed the existence of a large cystic mass in the submandibular gland. The patient was histopathologically diagnosed as pleomorphic adenoma by needle biopsy, and then the left submandibular gland was surgically removed under general anesthesia. Histopathological examination of the excised specimen showed remarkable cystic formation in the tumor parenchyma including the duct-like bilayered structure. Immunohistochemical staining revealed that the tumor cells expressed cytokeratin (AE1/AE3) and α-SMA, and S-100 protein was mainly expressed in the stromal cells. Furthermore, the Ki-67 labeling index of the tumor cells was less than 1%. The cystic wall mainly consisted of duct-like bilayered epithelium and α-SMA was expressed only in the basal layer. These histopathological findings suggested that the cystic lesion in this case might have been formed by enlargement of the duct-like structure in the tumor tissue. The histopathological diagnosis was finally pleomorphic adenoma. There has been no evidence of recurrence as of 1 year and 9 months after the operation.