Adenosquamous carcinoma of the pancreas: cytologic features in 14 cases

Adenosquamous carcinoma (ASCa) is a rare subtype of ductal adenocarcinoma of the pancreas with what to the authors' knowledge are limited cytologic descriptions. In the current study, the authors describe their experience with the fine-aspiration biopsy (FNAB) diagnosis of ASCa and characterize cytologic features in 14 cases.

Fourteen cases of ASCa were identified from pathology case files. Cytologic material was examined for cellularity, grade, tumor cell necrosis, and specific features of glandular and squamous differentiation.

The 10 females and 4 males had an average age of 70 years. Nine patients (64%) were reported to have Stage IV disease at the time of presentation. All tumors were high grade, with moderate to high cellularity. Tumor cell necrosis was noted in 12. Nine of the 14 cases (64%) demonstrated predominantly squamous differentiation with keratinization. Seven of these nine contained at least focal intracellular mucin or honeycombed glandular sheets. Two of the nine had rare cytoplasmic vacuoles as the only evidence of glandular differentiation. Five cases (36%) were predominantly glandular. All but one of these five cases contained atypical to malignant keratinized cells. One of the five cases lacked keratinization but had tumor cells with dense cytoplasm; the diagnosis of ASCa was confirmed on histology. In 13 patients for whom followup was known, 12 had died of disease (mean, 5.6 months) and 1 was alive at 13 months of follow-up.

A specific diagnosis of ASCa is possible when aspirates show evidence of both squamous and glandular differentiation, although one component often predominates and features of dual differentiation may be focal. A purely squamous tumor should raise the suspicion of a metastasis, but also may represent undersampling of an ASCa.