[Malignant fibrous histiocytoma of the thoracic region]

A clinicopathological investigation of five malignant fibrous histiocytoma (MFH) in the thoracic region was performed. They were two cases of metastasis to the lung and 1 each of the primary lesion in the lung, chest wall and sternal region. This tumor usually occurs on the extremities, in the abdominal cavity or the retroperitoneal areas, so instances of its arising in the thoracic region, except for metastatic episodes, are considered to be rare. Tumors in 4 cases were excised surgically, while one was inoperable. On light microscopy, the lesions were found to be composed of two types of neoplastic cells, fibroblast-like cells and histiocyte-like cells, showing the characteristic histologic pattern of storiform and pleomorphic. Electron-microscopically, these two types of cells were discriminated according to the quantitative and quantitative differences of the various intracytoplasmic organelles. The histogenesis of malignant fibrous histiocytoma has been commonly considered to be the histiocytic cell derived from the bone marrow. However, more detailed pathological investigations are necessary.