Oral adenosquamous carcinoma (ASC) is a rare and aggressive type of squamous cell carcinoma (SCC). It is characterized by a squamous component originating at the mucosa and a deep glandular component. ASC may be misdiagnosed as SCC by superficial incisional biopsy including only the squamous component. ASC has a worse prognosis than general variants of SCC, so accurate diagnosis is essential for patient survival. We present a case report of a large ASC arising in the buccal mucosa, first mistaken as general SCC.

Adenosquamous carcinoma (ASC) is a rare malignant epithelial tumor in the oral cavity. It is regarded as a variant of squamous cell carcinoma (SCC) because ASC originates from the surface epithelium, has similar clinical features, and includes SCC portion which is histologically identical to the traditional form. This case report deals with two cases of ASC occurring in the oral mucosa of old male patients. Both case has tubular structures lined by cuboidal, basaloid, or small round cells under the conventional SCC component, which was reminiscent of the glandular differentiation of adenocarcinoma. On immunohistochemical studies, the glandular component of ASC showed positivity to CK-pan, CK7 and HMWCK, while the dysplastic squamous cells exhibited negativity to CK7. Accordingly, CK7 as well as morphological findings can lead towards differentiating ASC from other variants with gland-like structures, such as basaloid squamous cell carcinoma and adenoid squamous cell carcinoma.