Das maligne fibr�se Histiozytom

Characterization of a Rat Subcutaneous Malignant Fibrous Histiocytoma and Its Tumor Lines, with Reference to Histiocytic Features

Malignant fibrous histiocytoma (MFH) is regarded as soft tissue-derived undifferentiated pleomorphic sarcoma, of which the histogenesis remains to be proven. To investigate the cellular characteristics, a homotransplantable tumor line (KJ) was established from a spontaneous MFH that developed in the subcutis of an aged F344 rat. KJ tumors have been produced in syngeneic rats by serial subcutaneous implantation of tissue fragments. The original and KJ tumors consisted of oval and fusiform cells arranged in interlacing bundles with fibrous stroma. Occasional giant cells with bizarre nuclei were observed. Enzyme/immunohistochemically, neoplastic cells reacted to ED1 and ED2 (antibodies specific for rat histiocytes/macrophages), and showed a positive reaction to vimentin and lysosomal enzyme markers such as acid phosphatase (ACP) and nonspecific esterase (Non-SE). Electron microscopically, neoplastic cells possessed lysosomal granules in cytoplasm. A cloned cell line (KJ-A) was isolated from a KJ tumor. KJ-A cells showed positive reactions to ED1, ED2, ACP, and Non-SE, and had cytoplasmic lysosomal granules. Tumors induced by KJ-A cells exhibited histologic and enzyme/immunohistochemical findings similar to those of KJ tumors. Lipopolysaccharide (LPS) treatment increased the number of ED1-positive cells and the expression of tumor necrosis factor-α mRNA by reverse transcription-polymerase chain reaction. Collectively, it is likely that rat MFH cells originally possess histiocyte/macrophage-like features that may be enhanced by LPS. Because tumor lines are useful for in vivo and in vitro studies concerning different characteristics of the original neoplasms. KJ and KJ-A should prove useful for studies concerning the morphogenesis of MFH.

Malignant fibrous histiocytoma: between the past and the present

The precise nature and diagnostic concept of malignant fibrous histiocytoma (MFH) has been debated for years. Currently, a histiocytic lineage of the tumor cells is no longer favored. The nomenclature and classification of MFH and its subtypes have also been changed. The MFH pattern, especially that of storiform-pleomorphic variant, is viewed as a morphologic pattern shared by a number of sarcomas as well as by other nonsarcomas. Therefore, a diagnosis of MFH based solely on morphology is no longer acceptable and identification of a line of differentiation should be sought. A diagnosis of MFH should be made only for pleomorphic sarcomas in which no specific line of differentiation is discerned. Precise categorization of MFH-like tumors may require thorough sampling of the tumor and judicious use of immunohistochemistry and/or electron microscopy. Familiarity with the current terminology and classification of MFH and its subtypes is of paramount significance in the modern practice of pathology.