Polypoid tumor of the esophagus.

Five cases of an uncommon esophageal tumor consisting of a mucosal squamous cell carcinoma that surrounds a polypoid mass of spindle cells were examined. The spindle cell component was composed of elongated cells with blunt nuclei, admixed with multinucleated giant cells. Reticulin fibers enveloped individual cells, and abundant collagen was present. Thirteen to 69 mitotic figures occurred per 10 high-power fields. Electron microscopy showed dilated cisternae of rough endoplasmic reticulum and peripheral intermediate filaments within the cytoplasm. Intermediate-type junctions (zonulae adherens) and subplasmalemmal linear densities connected some cells. No tonofibrillar bundles or desmosomes (maculae adherens) were present. Immunoperoxidase stains detected no keratin in the spindle cells. Alpha-1-antichymotrypsin and alpha-1-antitrypsin were in the spindle cells in five of five and three of five cases, respectively. The absence of desmosomes, tonofibrillar bundles, and keratin and the presence of alpha-1-antitrypsin and alpha-1-antichymotrypsin favor fibrohistiocytic differentiation of the spindle cell component.