Histological Description: There is a nodule of dense inflammation with scattered atypical cells. Most of the inflammation is lymphocytic but there is an admixture of plasma cells, and a few eosinophils. In the surrounding dense sclerotic fibroadipose tissue are scattered markedly atypical spindle cells with large hyperchromatic nuclei seen at low magnification. These cells have degenerative nuclear atypia with smudgy chromatin and a lack of mitotic activity.
Answer: B

Discussion: First, it is critical to recognize that the most common soft tissue paratesticular tumor is well-differentiated liposarcoma. Most well-differentiated liposarcomas in this region are lipoma-like with mature adipose tissue intersected by broad fibrous bands containing atypical spindle cells identical to those seen in the current case. Lipoblasts are typically not seen and not necessary to establish the diagnosis. There is also a sclerotic variant of well-differentiated liposarcoma which is similar to the lipoma-like subtype except there is a much higher proportion of sclerosis to mature adipose tissue. A much less common variant of well-differentiated liposarcoma is the inflammatory subtype. Microscopically, these tumors were characterized by areas of ordinary well-differentiated liposarcoma, admixed with discrete nodules comprised of small germinal centers, and separated by an admixture of lymphocytes, spindled stromal cells, collagen, and blood vessels, in which highly atypical tumor cells were embedded. The inflammatory component can almost obscure the atypical cells mimicking an inflammatory process or raising the differential diagnosis of various lymphoid neoplasms. This case was seen in consultation and submitted immunohistochemical stains were negative for CK7, S100 protein, CD30, CD45, Cd15, Oct ¾, EMA, CD68 and CD34. At our institution, MDM2 immunohistochemistry and MDMD2 RNA in-situ hybridization were performed showing positivity not only in the large atypical spindle cells in the sclerotic stroma but also in scattered atypical cells in the lymphoid nodule, verifying that both the sclerotic and inflammatory foci were both well-differentiated liposarcoma.

Lymphocyte-rich well-differentiated liposarcoma: report of nine cases. Argani P, Facchetti F, Inghirami G, Rosai J. Am J Surg Pathol. 1997 Aug;21(8):884-95.