Pleomorphic dermal sarcomaC49.-

Malignant fibrohistiocytic tumor that belongs to a small group of tumors formerly known as "malignant fibrous histiocytomas" (MHF). UPS is one of the most common soft tissue sarcomas in adults.

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

UPS is the de-differentiated form of many soft tissue tumors. The former histiocytic term pleomorphic "MFH" now only applies to those UPS forms for which no direction of differentiation (fibroblastic, myofibroblastic) can be detected.

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

Very heterogeneous, very cell-rich tumor masses or masses with a high proportion of connective tissue with conspicuous cytological and nuclear pleomorphism. Furthermore, bizarre giant tumor cells, spindle cells (fibroblastic, myofibroblastic or smooth muscle) and round histiocyte-like cells are found. A storiform growth pattern is detectable in sections. Furthermore inflammatory infiltrate cells.

Immunohistochemistry: Most UPS show a definable differentiation. Immunohistochemically, the main aim is to find 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.

PDS and atypical fibroxanthoma share common histopathologic and immunohistochemical features. Pleomorphic dermal sarcoma shows deeper tissue invasion and has a higher rate of metastasis and local recurrence than atypical fibroxanthoma. Given the aggressive clinical course, early detection and clinical management of PDS are critical to optimizing patient outcomes.

Prognosis 5-year survival 50-60%. However, the subgroups of pleomorphic sarcomas have different prognoses. For example, liposarcoma has a metastasis rate of 15-20%, high grade myxofibrosarcoma 30-35% and pleomorphic myogenic sarcoma a significantly higher rate (WHO Classification: Tumors of Soft Tissue and Bone, 2002).

1. Saleh JS et al. (2024) Pleomorphic dermal sarcoma. Surg Pathol Clin 17:153-158.