Adenosquamous carcinoma of the pancreas: A clinicopathologic series of 25 cases

Background: Adenosquamous carcinoma is a rare aggressive subtype of pancrea tic adenocarcinoma, We describe the clinical, pathologic, and molecular cha racteristics of 25 of these lesions, the largest series to date. Methods: T wenty-five cases of adenosquamous carcinoma of the pancreas diagnosed betwe en 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 pe rformed, 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 u sually experienced weight loss (n = 17) or painless jaundice (n = II), whil e also presenting with other abdominal symptoms. The tumors affected the he ad 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. Microsco pically, all tumors demonstrated dual differentiation toward adenocarcinoma and squamous cell carcinoma. All cases tested were immunoreactive with ker atin (AE1:AE3 and CK1), whereas other keratin markers were variably express ed: 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 mutati ons were identified in seven of 13 cases. AH patients died from their disea se an average of 5.8 months after diagnosis (range, 1 to 33 months). Conclu sions: Adenosquamous carcinoma of the pancreas represents a distinct clinic al and pathologic entity, demonstrating the expected immunoprofile and k-ra s oncogene mutation of a ductal origin, with a worse prognosis than ductal adenocarcinoma.