Warthin tumor (WT) is a common, benign, salivary gland neoplasm; it consists of a bilayered oncocytic epithelium lining a ductal, papillary, and cystic arrangement in an abundant lymphoid stroma. WTs mainly occur in the parotid gland and affect males in their sixth to seventh decade of life [
1]. WTs can show squamous metaplasia of the tumor epithelium; Seifert
et al. have reported metaplastic WTs with large areas of squamous metaplasia [
2]. Metaplastic WTs are rare, and their incidence ranges from 0% (0/278 cases) [
3] to 7.6% (21/275 cases) [
2]. Metaplastic WTs can also be called infarcted WTs because they are occasionally accompanied by extensive necrosis, fibrosis, and inflammation [
4]. Metaplastic WTs may develop mucinous epithelial metaplasia [
5,
6], which can pathologically mimic a low-grade mucoepidermoid carcinoma (MEC). WTs rarely coexist with malignant epithelial neoplasms, such as the squamous cell carcinoma (the most common [
7]) and MEC; 27 cases of MEC in or coexisting with WT have been described [
7‐
21]. Pathological differentiation of a metaplastic WT from a MEC can be difficult because some metaplastic WTs have been reclassified as MECs based on clinicopathological and genetic studies [
17,
22]. Thus, the use of a pathological diagnosis only has limitations in distinguishing metaplastic WTs from MECs. Most MECs are genetically characterized by a t(11;19)(q21;p13) translocation and a
CRTC1-
MAML2 gene fusion or a t(11;15)(q21;q26) translocation and a
CRTC3-
MAML2 gene fusion [
23]. Typical WTs and metaplastic WTs are considered to have no translocations seen in MECs [
22,
24‐
26]; however, a few opposite results have been previously reported [
27,
28]. Fluorescence
in situ hybridization (FISH) to detect
MAML2 gene rearrangement appears to serve as one of the useful tools to clarify whether the metaplastic portions of WTs are different from the MECs or whether they could be the origin of MECs. The present case is of an infarcted WT with MEC-like metaplasia, and it appears to be the third reported case [
5,
6]. We performed a pathological and genetic evaluation to make the distinction between tumor metaplasia and MEC.