Warthin-like mucoepidermoid carcinoma of the parotid gland: Clinicopathological observation and literature review

Abstract

Warthin tumor (WT)-like mucoepidermoid carcinoma resembles the histologic pattern of WT and pathologists unaware of this possibility may misdiagnose it as WT with squamous and mucous epithelium metaplasia or WT malignant transfer into mucoepidermoid carcinoma. The present study reported a case of a 41-year-old Chinese female with a solitary mass in the left parotid gland. In this case, microscopic observation revealed prominent lymph node stroma and multiple cystic structures similar to those seen in WT. However, it lacked the two layers of oncocytic epithelial tissue characteristic of WT. Furthermore, fluorescence in situ hybridization detected MAML2 rearrangement in the case. Considering the histological findings, this case was diagnosed as WT-like mucoepidermoid carcinoma. The present case report provides pathological and clinical features to differentiate it from WT malignant transition into mucoepidermoid carcinoma, WT with squamous and mucous epithelium metaplasia and non-sebaceous lymphadenoma-like mucoepidermoid carcinoma. In conclusion, WT-like mucoepidermoid carcinoma as a special subtype of mucoepidermoid carcinoma has special histological characteristics, which required further observations and more case reports to clearly define this variant.

Warthin-like Variant of Mucoepidermoid Carcinoma of the Parotid Gland

“…2 Only 28 cases are reported in the literature and most appear to have a slow biological behavior with no recurrence or metastasis after total parotidectomy. 3 Although the literature supports classifying WL-MEC as a low-grade form of MEC, in the current case, the authors decided to still mention the grade in the diagnosis to facilitate communication with the managing clinical service as the management of WL-MEC follows that of conventional MEC wherein low-grade lesions are treated with surgery alone. 3 Because of the presence of oncocytes in a dense lymphoid background, the most cogent morphological differential diagnosis is a Warthin Tumor -a benign salivary gland tumor characterized by glandular spaces lined by oncocytes and similarly surrounded by abundant lymphocytes.…”

“…3 Although the literature supports classifying WL-MEC as a low-grade form of MEC, in the current case, the authors decided to still mention the grade in the diagnosis to facilitate communication with the managing clinical service as the management of WL-MEC follows that of conventional MEC wherein low-grade lesions are treated with surgery alone. 3 Because of the presence of oncocytes in a dense lymphoid background, the most cogent morphological differential diagnosis is a Warthin Tumor -a benign salivary gland tumor characterized by glandular spaces lined by oncocytes and similarly surrounded by abundant lymphocytes. The most helpful finding in distinguishing the two is that WL-MEC lacks the well-arranged, bilayered oncocytic epithelium characteristic of Warthin Tumor (WT) and is instead characterized by a haphazard proliferation of the tumor cells.…”

“…The most helpful finding in distinguishing the two is that WL-MEC lacks the well-arranged, bilayered oncocytic epithelium characteristic of Warthin Tumor (WT) and is instead characterized by a haphazard proliferation of the tumor cells. 3 In addition, the infiltrative border of a carcinoma differs from the wellcircumscribed and encapsulated one of a benign lesion such as WT.…”