Metastatic atypical meningioma to the parotid gland - A cytopathological correlation

Abstract

The tumors involving the parotid gland are mainly primary, with metastatic lesions comprising only 5% of malignant salivary gland neoplasms. We are presenting a rare case of metastatic meningioma to the parotid in a 51-year-old male with a past medical history of recurrent atypical meningioma involving the frontal lobe. For the past 1.5 years, routine imaging showed parotid lesions with interval growth including a 2.0 cm dominant tender preauricular parotid mass. The chronicity and the number of lesions made malignancy unlikely. The differential diagnosis included non-specific lesions such as intraparotid lymph nodes and benign neoplasms. Fine needle aspiration of the parotid mass was performed to show loosely cohesive fragments and singly scattered neoplastic cells with mild nuclear pleomorphism and oncocytic cytoplasm. The main cytomorphologic differential diagnosis included oncocytic and myoepithelial-rich tumors. The neoplastic cells were immunoreactive to p63, calponin and SSTR2A and were negative for cytokeratins, progesterone receptor, S100, DOG-1, EMA, synaptophysin, and chromogranin. The cytology slides and the parotid gland mass resection were compared to the previous meningioma resection specimen which showed a similar morphology of the oncocytic tumor cells in some areas. The overall morphologic and immunohistochemical findings of the parotid tumor were consistent with metastatic meningioma. Extracranial metastases from intracranial tumors are extremely rare. Meningiomas arise from the dura matter, constitute 15% of primary brain tumors, and metastasize at an estimated rate of 0.1%. Despite how uncommon metastatic meningioma is, our case emphasizes the critical role of clinical history when evaluating parotid gland lesions.

Keywords: Meningioma; Metastasis to the parotid gland.