Malignant epithelioid peripheral nerve sheath tumor arising in a benign schwannoma

The case of a patient with malignant degeneration of a solitary abdominal schwannoma and endobronchial metastasis is presented. The patient presented clinically with dyspnea referable to her lung mass, anorexia, and night sweats. The lung mass, initially diagnosed as a large-cell undifferentiated carcinoma, was later found to be histologically identical to the malignant portion of the abdominal tumor. The light microscopic, electron microscopic, and immunoperoxidase staining characteristics of the tumor are reported, and previous reports in the literature are reviewed.

Common leukocyte antigen staining of a primitive sarcoma

A 4-year-old boy presented with symptoms of tracheal obstruction and was found to have a polypoid tracheal mass, which was studied by biopsy. Light microscopy showed a tumor composed of small cells with round to oval dark nuclei, clumped chromatin, one to two nucleoli, and small, variable amounts of indistinct pink cytoplasm. In other areas the tumor had a loose, spindle appearance, with some cells showing more elongated nuclei, and fibrillar pink cytoplasm consistent with strap cells. Cross striations were not found. Electron microscopy showed desmosomes and 7 to 10 nm cytoplasmic filaments forming dense bodies. The findings are most consistent with a primitive sarcoma, probably rhabdomyosarcoma. Immunoperoxidase with three monoclonal antibodies for common leukocyte antigen showed diffuse membraneous staining with fresh-frozen tissue. All other lymphocyte and monocyte marker studies were negative. We believe that this case of anticommon leukocyte antigen staining, a rhabdomyosarcoma, represents the first report of a false positive reaction with monoclonal antibody to common leukocyte antigen.