Sarcomatoid carcinoma of the pancreas: a case report with immunohistochemical study.

Sarcomatoid carcinoma of the pancreas is an uncommon neoplasm. The immunohistochemical characteristics of this unique type of pancreatic tumor were studied. Histologically, there was diffuse proliferation of atypical spindle cells that had hyperchromatic, short, spindle-shaped nuclei and pale cytoplasm. A few tiny foci of small tubular structures were seen in connection with the atypical spindle-shaped cells. Immunohistochemical examination showed that the spindle cells were positive for epithelial cell markers (cytokeratin AE3, cytokeratin AE1, epithelial membrane antigen) and DF3 (MUC1 apomucin-related antigen (ARA)), and were negative for markers such as vimentin, desmin, neuron-specific enolase, and myoglobin. DF3 antigen is known to be expressed in invasive ductal carcinoma of the pancreas and liver, as well as of the breast. Other MUC1-ARA (MY.1E12, MUC1 glycoprotein, HMFG-1, HMFG-2) and anti-CA19-9 were also detected in the present case. Thus, this tumor was diagnosed as anaplastic carcinoma (sarcomatoid carcinoma).