Cutaneous soft tissue sarcomas are a heterogeneous group of mesenchymal neoplasms. Kaposi sarcoma is among the most common CSTS, followed by dermatofibrosarcoma protuberans, malignant fibrous histiocytoma, leiomyosarcoma, and angiosarcoma [1
]. Other specified and no specified CSTS represent approximately 1.8% [1
]. Malignant mesenchymoma (MM) is a sarcoma that exhibits two or more lines of specialized differentiation [1
]. Our case showed definite pleomorphic liposarcoma and conventional osteosarcoma, so the diagnosis of MM was authentic according to the criteria presented in the WHO classification of tumors of soft tissue and bone. We present a case of MM, consisting of pleomorphic liposarcoma and conventional osteosarcoma in the cutaneous region that was diagnosed using a combination of morphologic and immunophenotypic characterizations. To the best of our knowledge, this is the first case report to describe this unusual combination presenting in the cutaneous region.
It has become apparent that MM does not make up a clinicopathological entity, and those potential candidates for the designation can be more appropriately classified in other ways [1
]. Actually, sarcomas displaying two or more lines of differentiation are best diagnosed by identifying the lines of differentiation, their approximate amounts, and the grade of the most aggressive component [10
]. If we address this change of concept, purely dermal liposarcoma is exceedingly rare [11
]. In pleomorphic liposarcoma, nonlipogenic described areas are characterized by malignant fibrous histiocytoma-like, round cell liposarcoma-like, epithelioid/carcinoma-like features and/or cartilaginous, osseous, smooth muscle or skeletal muscle elements [16
]. Our case represents an unusual combination of two exceedingly rare combined sarcomas in the cutaneous region.
The differential diagnosis of sarcoma, in the cutaneous region, includes atypical fibroxantoma, sarcomatoid carcinoma, melanoma, malignant fibrous histiocytoma, fibrosarcoma, leiomyosarcoma, and rhabdomyosarcoma. The spindled variant of atypical fibroxanthoma (AFX) shows similar histopathologic findings, and most reliable markers to differentiate AFX from another sarcomas are CD10 and S-100. AFX is usually positive for CD10 and S-100 is only expressed in dendritic cells (Langerhans cells), which are nonneoplastic cells commonly present within AFX [17
]. Sarcomatoid carcinoma shows pleomorphic areas and cytokeratin, p63 expression. The last immunoprofile should be taken into consideration carefully, because liposarcoma and osteosarcoma can showed positivity to this antibodies, and erroneous conclusive diagnosis can be made in small biopsies. Another important differential diagnoses are melanoma and malignant peripheral nerve sheath tumor (MPNST), because these lesions are S-100 positive. However, HMB45 and Melan A are usually positive in melanoma and negative for liposarcoma or osteosarcoma. Smooth muscle actin, desmin, and myoglobin D1 can be used to establish the diagnoses of leiomyosarcoma, rhabdomyosarcoma.
In summary, we report a case of an 81-year-old woman presenting with tumor in the cutaneous region. Combined cutaneous sarcoma was diagnosed by integrating histological and immunophenotypic studies. It is a rare tumor in an uncommon site, and in this paper we review the entity, as well as the main histological differential diagnosis.