Spindle cell rhabdomyosarcoma. A prognostically favorable variant of rhabdomyosarcoma.

Twenty-one cases of embryonal rhabdomyosarcoma, composed mainly of elongated spindle cells arranged in a fasciculated or storiform pattern, were retrieved from the files of the German-Italian Cooperative Soft Tissue Sarcoma Study. The term spindle cell rhabdomyosarcoma is proposed to designate this histotype. Spindle cell rhabdomyosarcoma predilected male patients (18 males, three females) and involved mostly the paratesticular area (12 cases) and the head and neck region (six cases). Histologically, all cases were characterized by a uniform proliferation of elongated spindle cells with eosinophilic and fibrillar cytoplasm mimicking smooth muscle fibers; immunocytochemical studies disclosed high expression of the muscle markers titin, desmin, and myoglobin. Clinical information was available in 17 cases; according to the Intergroup Rhabdomyosarcoma Study (IRS) grouping system, 13 were classified in group I, two in group II, and two in group III. Sixteen patients were well and alive 24 to 100 months after diagnosis; one patient died from disease progression 24 months after diagnosis. Analysis of our results determined that spindle cell rhabdomyosarcoma constitutes a rare variant of the embryonal form, showing a high degree of skeletal muscle differentiation and a low malignant potential; it should therefore be distinguished from classical forms of embryonal rhabdomyosarcoma.

Small-cell carcinoma of gallbladder. An immunocytochemical and ultrastructural study.

An unusual carcinoma of the gallbladder in a seventy-one-year-old woman displayed features of a well-differentiated adenocarcinoma, atypical carcinoid and small cell undifferentiated carcinoma. The patient died from progressive hepatic failure four months after surgery. Autopsy showed bulky liver masses and several peritoneal nodules exclusively composed of small, hyperchromatic cells. The neuroendocrine nature of the small cell component of the tumor was documented by the presence of neurosecretory granules at the ultrastructural level and by immunocytochemical positivity to NSE and Synaptophysin. The epithelial markers, cytokeratin and CEA, were also positive in the carcinoid and in the undifferentiated portions of the tumor. A common endodermal origin is suggested for carcinoid and small cell carcinoma of the gallbladder.

Therapy associated differentiation in rhabdomyosarcomas.

The morphologic and immunophenotypical features of three embryonal and one spindle cell rhabdomyosarcomas that underwent marked cytologic differentiation after polychemotherapy are described. In all the cases the morphologic changes were associated to disappearance of vimentin immunoreactivity and intense positivity for desmin, muscle specific actins, and myoglobin; in addition the differentiated tumor cells acquired a strong and continuous pericellular staining for laminin. The mitotic activity was significantly decreased. Drug associated differentiation seems to recapitulate the normal myogenic development to the point that the more mature neoplastic cells may represent terminally differentiated elements withdrawn from cell cycle. However, due to the persistence of a small number of poorly differentiated rhabdomyoblasts, the clinical consequences of this phenomenon are unclear.