Dermal undifferentiated pleomorphic sarcoma C49.-

Malignant fibrohistiocytic tumor that belongs to a small group of tumors that were formerly called malignant fibrous histiocytomas. UPS is one of the most common soft tissue sarcomas in adults.

Reliable incidence rates are not available. m:w=1.2:1

Dermal undifferentiated pleomorphic sarcomas of the skin can preferably be found just like AFX in actinic damaged skin of older patients.

• Very heterogeneous tumour masses, very rich in cells or with a high proportion of connective tissue, with conspicuous cytological and nuclear pleomorphism. Bizarre tumor giant cells, spindle cells (fibroblastic, myofibroblastic or smooth muscle) and round histiocyte-like cells are also found. A storiform growth pattern can be detected in sections. Furthermore inflammatory infiltrate cells.
• Immunohistochemistry: Most UPS show a definable differentiation. Immunohistochemistry is mainly concerned with finding a differentiation from non-mesenchymal malignant tumors.
• Molecular pathology: The karyotypes of UPS are very complex and heterogeneous. Aneuploidy is frequent. Loss of 2p24-pter, 2q32-qter, 11, 13, 16; gain of 7p15-pter, 7q32 and 1p31. Amplification of some proto-oncogenes in 12q13-15: SAS, MDM2, CDK4, DDIT3, HMGIC and 8p23.1:MASL1.
• Detection of mutations or deletions in TP53, RB1(retinoblastoma protein - see ERK below), CDKN2A and HRAS.

Immunohistochemical examination: CD10, CD68, FactorXIIIα, S100, MelanA, SOX10, CKAE1/AE3, p63, CD34

Microscopic examination: Histologically, the described tissue fragment corresponds to a tumor section without epithelial covering. In the vascular fibrous layer of the above biopsy section of the tumor, the presence of atypical pleomorphic cells, the type of atypical polygonal cells, atypical spindle cells and of atypical giant cells, some of which are multinucleated.

Immunohistochemistry: In the immunohistochemical study, the neoplastic cells are: CD10(+), CD68(+), FactorXIIIα(+), S100(-), MelanA (-), SOX10(-), CKAE1/AE3(-), p63(-), CD34(-).

Conclusion/comment: Section of a skin tumor with individual morphological and immunohistochemical elements that cannot be evaluated as pathognomonic. Among other things, in the present section of the tumor, a question of histological differential diagnosis arises mainly between the segment of atypical fibroxanthoma and the segment of pleomorphic cutaneous sarcoma.