Electron microscopy in the diagnosis of malignant fibrous histiocytoma of the lung presenting as metastasis to the maxillary gingiva.

A rare case of an initial presentation of a metastatic lesion on the gingiva, arising from malignant fibrous histiocytoma (MFH) of the lung is reported. The role of electron microscopy in the diagnosis of soft tissue sarcomas has been studied. The ultrastructural details of a MFH are described and illustrated. The patient died within 9 weeks of the initial presentation with a gingival mass as is normal in these cases. He developed metastatic disease of the liver, lymph nodes, and bone. The role of electron microscopy in the diagnosis of soft tissue sarcomas is discussed.

Low-grade myxofibrosarcoma invaded into the underlying skeletal muscle.

Myxofibrosarcoma is a rare, soft-tissue sarcoma which is classified into three main subtypes according to cellularity and cell atypia: low, intermediate and high grade. A 44-year-old Japanese female presented with a low-grade myxofibrosarcoma on the left forearm. The lesion was completely resected. Histopathologically, the tumor was remarkably hypocellular and exhibited only mild atypia. However, it rapidly invaded into the underlying brachioradial muscle. The present case clearly indicated that a low-grade myxofibrosarcoma can invade into the deeper tissues including muscle even though its histological grade is very low.

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-alpha 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 of bone: an ultrastructural study.

An ultrastructural study of a case of malignant fibrous histiocytoma of bone in a 16-year-old skeletally mature female is presented. There were multiple metastatic bone lesions and a marked hypercalcemia. The cell population was similar to that found in soft tissue malignant fibrous histiocytoma lesions and comprised undifferentiated cells, fibroblastlike cells, histiocytes, and multinucleated giant cells. Occasional myofibroblasts and transitional cells with histiocytic and fibroblastic components were seen. The histiocytes were characterized by prominent Golgi bodies. Although there were many fibroblastlike cells, the rough endoplasmic reticulum was rarely as extensive or as well organized as in normal fibroblasts. The giant cells did not have the ultrastructural characteristics of osteoclasts, i.e., the clear zones and ruffled borders. Zonula adherens (belt desmosome) junctions were seen, but in general, intercellular junctions were poorly developed as to length and extent.