Ultrastructural and histochemical identification of sclerosing liposarcoma

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Abstract
A paratesticular tumor [from a human] by light microscopy showed large amounts of partly hyalinized collagenous stroma, spindle shaped fibroblast-like cells, pleomorphic cells with foamy cytoplasm, multinucleated tumor type giant cells and lipid inclusions. By light microscopy, there was a problem as to whether the tumor should be classified with the liposarcomas or with the fibrous histiocytic group. Ultrastructurally, spindle shaped cells resembled fibroblasts and, in a few cells, intracellular collagen fibers were seen. Histochemical studies revealed the presence of mannose-rich glycoprotein which is characteristic for collagen producing cells but frequently these cells also showed numerous lipid inclusions. The foamy cytoplasmic areas of pleomorphic cells consisted of dilated ergastoplasmic sacs and large vacuoles lined by smooth endoplasmic reticulum negating the possiblity that these cells were of histiocytic origin. This is supported further by the dearth of lysosomes and absence of lysozyme (muramidase) in the tumor cells. The presence of numerous lipid inclusions in many of the tumor cells, which are otherwise ultrastructurally similar to fibroblasts, suggests that these cells represent precursors of lipoblasts. The above findings taken together allowed the tumor to be categorized as a sclerosing liposarcoma.