Adenosquamous carcinoma of the pancreas: a clinicopathologic series of 25 cases.

BACKGROUND: Adenosquamous carcinoma is a rare aggressive subtype of pancreatic adenocarcinoma. We describe the clinical, pathologic, and molecular characteristics of 25 of these lesions, the largest series to date.
METHODS: Twenty-five cases of adenosquamous carcinoma of the pancreas diagnosed between 1961 and 1994 were retrieved from the files of the Endocrine Registry of the Armed Forces Institute of Pathology. Histologic features were reviewed, histochemical, immunohistochemical, and molecular (k-ras) studies were performed, and patient follow-up was obtained.
RESULTS: The patients included 17 men and eight women, aged 28 to 82 years (mean, 65.4 y). The patients usually experienced weight loss (n = 17) or painless jaundice (n = 11), while also presenting with other abdominal symptoms. The tumors affected the head most frequently (n = 17), followed by the tail (n = 9) or body (n = 4). Five cases involved more than one anatomic region of the pancreas. Microscopically, all tumors demonstrated dual differentiation toward adenocarcinoma and squamous cell carcinoma. All cases tested were immunoreactive with keratin (AE1:AE3 and CK1), whereas other keratin markers were variably expressed: CK5/6 (88%), CK7 (68%), Cam5.2 (41%), and CK20(26%). CA-19-9 (84%) and CEA (74%) were positive in the majority of the cases. K-ras oncogene mutations were identified in seven of 13 cases. All patients died from their disease an average of 5.8 months after diagnosis (range, 1 to 33 months).
CONCLUSIONS: Adenosquamous carcinoma of the pancreas represents a distinct clinical and pathologic entity, demonstrating the expected immunoprofile and k-ras oncogene mutation of a ductal origin, with a worse prognosis than ductal adenocarcinoma.