Immunohistochemical characteristics of adenosquamous carcinoma of the pancreas.

Six patients with adenosquamous carcinoma (ASqC) of the pancreas were studied clinicopathologically and immunohistochemically. In five of six ASqC tumors, both malignant squamous and glandular elements were reactive with CA 19-9, ST 439, and keratin antibodies. In contrast, a portion of the glandular element in the remaining one ASqC was reactive with CA 19-9 and ST 439 antibodies, but that of the squamous cell carcinoma (SqCC) was not reactive. However, SqCC of this tumor was intensely reactive with keratin antibody. These immunohistochemical results suggest that the histogenesis in one ASqC tumor was different from that of the other 5 ASqCs, and that this tumor may be a collision tumor rather than transformation to SqCC from adenocarcinoma, which is a very rare pattern of histogenesis in ASqC. The patients with ASqC of the pancreas showed shorter survivals following operations because of systemic metastasis including liver metastasis.