Soft tissue tumors : A basic research for improving the accuracy of pathologic diagnosis using immunohistochemical and cytogenetic analysis.

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The diagnosis of soft tissue tumors is often very difficult, since they show a wide spectrum of histologic features ranging from reactive inflammatory lesions to malignant tumors. We investigated various soft tissue tumors in an attempt to clarify their morphologic, immunohistochemical and cytogenetic characteristics and to evaluate whether these parameters are helpful in diagnosing difficult cases of soft tissue neoplasms.(1) Our study demonstrated that the proliferative compartment of dermatofibroma is composed chiefly of mesenchymal/fibroblastic lineage, accompanied by varying numbers of normal reactive histiocytes.(2) Epithelioid sarcoma is a peculiar soft-tissue neoplasm of uncertain origin, which is characterized by an epithelioid morphology of tumor cells coexpressing epithelial (keratin) and non-epithelial (vimentin) antigens. We found a new cytogenetic abnormality with der (22) t (18 ; 22) (q11 ; p11.2) in a case of epithelioid sarcoma that occurred in the elbow of a 75-year-o … More ld man. Histologically, the tumor demonstrated a multinodular proliferation of epithelioid cells, with positive immunostaining for keratin, epithelial membrane antigen (EMA), and vimentin. Since the breakpoint at 18q11 is similar to that reported in synovial sarcoma, this finding may support the presence of a histogenetic relationship between epithelioid sarcoma and synovial sarcoma.(3) Renal primitive neuroectodermal tumor (PNET) is very rare. Although only 3 such cases have been previously reported, none of them were confirmed by cytogenetic and melecular studies. We reported two cases of renal PNET,in which the diagnosis was established by both cytogenetic and molecular analysis. In each tumor, the cytogenetic analysis with in situ hybridization (chromosome painting) demonstrated reciprocal translocation t (11 ; 22) (q24 ; q12) specific to PNET.One patient presenting a fetal outcome had an additional chromosome abnormalities of extra 1q and deletion of 16q13. The RT-PCR in both tumors demonstrated EWS/FLI-1 fusion transcripts, representing the molecular equivalent of t (11 ; 22).(4) In an analysis of 103 soft-tissue and bone tumors, we detected supernumerary ring chromosomes in 6 cases of low-grade soft tissue tumors including 5 cases of atypical lipomatous tumors (ALT) (atypical intramuscular lipoma, 1 ; well differentiated liposarcoma, 4[lipoma-like type, 2 ; sclerosing type, 1 ; inflammatory type, 1]and one case of dermatofibrosarcoma protuberans (DFSP). Our findings suggest that supernumerary ring chromosomes are characteristic of low-grade soft tissue neoplasms including ATL and DFSP and that cytogenetic analysis is thus prove helpful in diagnosing such difficult cases of low-grade neoplasms. Less