Sarcomatoid carcinoma of the pancreas presenting as gastric carcinoma: clinicopathologic and ultrastructural findings.

The clinicopathologic and ultrastructural features of a sarcomatoid carcinoma of the pancreas presenting initially as gastric carcinoma are described. By light microscopy, the tumor contained cellular patterns similar to those present in tumors of mesenchymal origin. Spindle cell areas arranged in a storiform pattern were present. Ultrastructurally, bundles of cytoplasmic microfilaments were present in the cell cytoplasm and were similar in distribution to those found on fine structural examination in tumors of mesenchymal origin. Rows of desmosomes were found between cells supporting an epithelial origin for this tumor. Following initial therapy, metastatic tumor produced polypoid lesions in the small intestine resulting in recurrent small bowel intussuceptions. Our findings indicate that sarcomatoid carcinoma of the pancreas, by both light and ultrastructural examination, is a heterogenous tumor at the cellular level and may be a cause of repeated intussuception when intraluminal compromise occurs.