Extrapleural Solitary Fibrous Tumor A clinical & pathological study of 8 cases

We reviewed eight solitary fibrous tumors occurring at sites other than pleura (three orbit, two retroperitoneum, one each hard palate, thyroid, and tongue) which shared the histologic and immunohistochemical features of solitary fibrous tumors of pleura. Six patients were women, and two were men, aged from 26 to 74 years. The tumors ranging from 1.5 to 19 cm in diameter presented as well-circumscribed, unencapsulated, soft to rubbery tissue masses. Histologically they were characterized by a proliferation of spindle or ovoid cells intervened by a dense bundles of collagen. A variety of growth patterns was identified but the so-called patternless pattern was the predominant one. One tumor exhibited highly cellular sarcomatous areas with extensive necrosis, which was diagnosed as malignant solitary fibrous tumor. Immunohistochemical studies showed that all of the tumors were strongly positive for both CD34 and vimentin, but negative for cytokeratin, S-100 protein, EMA, and desmin. One case examined ultrastructurally showed features of fibroblast. All but one showed no evidence of recurrence or metastasis over follow-up period of 14 to 32 months. We conclude that extrapleural solitary fibrous tumors represent a distinct mesenchymal tumor with variable histologic features and should be differentiated from other spindle cell mesenchymal tumors.

A Case of Malignant Extrarenal Rhabdoid Tumor

Malignant Rhabdoid tumor is a rare malignant neoplasm and is morphologically similar to rhabdomyosarcoma, but is different immunohistochemically. Most malignant rhabdoid tumors occur in the kidney of infants, and are rarely reported at extrarenal sites. Since Frierson and his collagues first described the malignant extrarenal rhabdoid tumor(MRT) in children in 1985, it has rarely been reported. The neoplasm is histologically and immunohistochemically identical to a renal malignant rhabdoid tumor. There have been no previous reports of this neoplasm in Korea. An MRT of the sacroiliac bone in a 11-year-old girl is described. Five months after the initial presentation, the patient is still alive with partial response to combination chemotherapy and radiotherapy. The authors review previous reports of extrarenal MRT, and discuss the pathologic characteristics, differential diagnosis, and treatment of this rare neoplasm.