Pulmonary adenosquamous carcinoma with mucoepidermoid carcinoma-like component with characteristic p63 staining pattern: either a novel subtype originating from bronchial epithelium or variant mucoepidermoid carcinoma

Abstract

Background: Our previous study found unique adenosquamous carcinomas (ADSQs) containing a mucoepidermoid carcinoma (MEC)-like component and a characteristic p63 staining pattern. This study focused on these unique ADSQs.

Methods: Thirty ADSQ cases were studied histologically and by immunohistochemistry for TTF-1 and p63. Of these 30 ADSQs, eight were selected as unique ADSQs. The clinicopathological characteristics of these ADSQs were further studied, and the gene rearrangement of mammalian mastermind-like 2 (MAML2) was investigated by fluorescence in situ hybridization (FISH) for differentiation from pulmonary MEC.

Results: The clinicopathological characteristics between the eight ADSQs and the other ADSQ cases showed no statistically significant differences, except for serum CEA level. Histologically, the eight ADSQs contained varying degrees of the MEC-like component, which consisted of solid nests with mucin-filled cysts or a cribriform-like structure. Immunohistochemically, p63-positive nuclei characteristically encircled the tumor nests, although TTF-1 was completely negative. All unique ADSQs not only had a variable degree of squamous cell carcinoma component in addition to the MEC-like component, but also contained a small tubular adenocarcinoma component in three tumors. FISH analysis revealed no MAML2 gene rearrangement in the eight ADSQs.

Conclusions: Of the 30 ADSQs investigated in this study, eight contained a MEC-like component with a characteristic p63 basilar staining pattern similar to that of bronchial basal cells. These unique ADSQs shared clinical characteristics with ordinary ADSQs, but clinicopathologically differed from pulmonary ordinary MEC. Therefore, these unique ADSQs may be either a novel ADSQ subtype originating from bronchial epithelium or variant-type MEC.

Keywords: Adenosquamous carcinoma; Bronchial basal cell; Lung cancer; Mammalian mastermind-like 2; Mucoepidermoid carcinoma; p63.