High-Grade Mucoepidermoid Carcinoma Ex-Pleomorphic Adenoma of the Parotid Gland: Case Report and Review of Literature

Abstract

Background: Mucoepidermoid carcinoma ex-pleomorphic adenoma (MECxPA) is an extremely rare salivary gland malignancy. With only nine prior reported cases, this entity represents a challenging histopathological diagnosis. Methods: We present a case of a 71-year-old male with an enlarging left neck mass over several months. CT showed both a parapharyngeal space mass and a separate level II neck mass. Results: The patient underwent resection of the left parapharyngeal mass and ipsilateral selective level II-IV lymphadenectomy. The final pathologic diagnosis was metastatic high-grade mucoepidermoid carcinoma ex-pleomorphic adenoma. Conclusions: We describe a novel presentation of high-grade mucoepidermoid carcinoma ex-pleomorphic adenoma as a metastatic parapharyngeal mass.

Carcinoma ex pleomorphic adenoma: A diagnostic challenge on cytology

“…Salivary duct carcinoma is a rare but aggressive malignancy and histologically resembles the ductal carcinoma of breast . In this case, malignant tumor cells were strongly positive for CK‐7 and GCDFP‐15, indicating Ca ex PA with salivary duct carcinoma as the malignant component . Staining for myoepithelial marker p63 was positive focally in benign myoepithelial cells.…”

“…Ca ex PA may not be clinically symptomatic and may present as benign pleomorphic adenoma . The signs and symptoms associated with carcinomatous transformation of PA include rapid growth, change in consistency, pain and facial nerve paralysis . The patient in our case presented with rapid increase in the size of a longstanding parotid mass along with history of weight loss.…”

“…15 In this case, malignant tumor cells were strongly positive for CK-7 and GCDFP-15, indicating Ca ex PA with salivary duct carcinoma as the malignant component. 6,13 Staining for myoepithelial marker p63 was positive focally in benign myoepithelial cells. The malignant tumor cells being negative for CK-5/6 ruled out squamous cell carcinoma.…”

“…13 For the determination of the specific nature of malignant salivary tumor as well as a precise classification and grade, FNAC cannot be relied upon. 8 The reasons could be the needle miss in a hetereogeneous tumor, 6 the malignant component can be missed in cases where it is too small and the benign component may be missed in cases where the entire gland is being replaced by carcinoma. 14 In this case, multiple passes were done from different sites and a provisional diagnosis of Ca ex PA was suggested in cytological smears which showed pleomorphic malignant cells in a background of pleomorphic adenoma.…”

Mucoepidermoid Carcinoma Ex-Pleormorphic Adenoma of Parotid Gland: A Rare Variant with Cytodiagnostic Handicap

“…It develops in 6% of all pleomophic adenomas and is defined as a carcinoma that arises in the epithelial and/or myoepithelial component of the tumor (1). This entity accounts for about 11% of all salivary gland malignancy and often involves patients in their sixth to seventh decades of life and exhibits variable gender predilection (2). The rarity of this malignancy coupled with a subtle presentation mimicking the benign counterpart poses a challenge in terms of diagnosis and timely management.…”