Epithelioid malignant peripheral nerve

KER, keratin, as detected by a mixture of CAM5.2, MAK-6, and AEl /AE3 EMA, epithelial membrane antigen VIM, vimentin DES, desmin MSA, muscle-specific actin SMA, smooth muscle (alpha isoform) actin CALD, h-caldesmon S-IOOP, S-100 protein TY, tyrosinase Ml, MART-1 (melan-A) OGN, osteocalcin EPS, epithelioid sarcoma EPSS, epithelioid synovial sarcoma EAS, epithelioid angiosarcoma EMPNST, epithelioid malignant peripheral nerve sheath tumor CCS, clear cell sarcoma SEFS, sclerosing epithelioid fibrosarcoma ... 

Epithelioid Malignant Peripheral Nerve Sheath Tumors... 

Epithelioid synovial sarcoma is reactive for keratin in 100% of cases and Ber-EP4 in 90% of cases. Epithelioid malignant peripheral nerve sheath tumor is reactive for S-1 00 protein in 80% of cases. 

Fetal fibroblasts myometrium vascular smooth muscle fetal myocardium vascular endothelial cells selected reticulum cells of lymphatic organs some CD30+ lymphoid cells (rarely) selected leiomyosarcomas, epithelioid hemangioendotheliomas, epithelioid angiosarcomas, primitive neuroectodermal tumors and Ewing s sarcomas, malignant peripheral nerve sheath tumors, and clear cell sarcomas... 

Keratins are regularly found in synovial sarcoma, chordoma, parachordoma, epithelioid sarcoma, and adamantinoma. They are seen less commonly in leiomyosarcoma, malignant peripheral nerve sheath tumors, epithelioid angiosarcoma, and polyphenotypic tumors such as PNET. 

Laskin WB, Weiss SW, Bratthauer GL. Epithelioid variant of malignant peripheral nerve sheath tumor (malignant epithelioid schwannoma). Am J Surg Pathol. 1991 15 1136-1145. 

Hoang MP, Sinkre P, Albores-Saavedra J. Expression of protein gene product 9.5 in epithelioid and conventional malignant peripheral nerve sheath tumors. Arch Pathol Lab Med. 2001 125 1321-1325. 

The ability of melanoma to simulate the appearance of various soft tissue sarcomas is also well documented. These include malignant peripheral nerve sheath tumors, gastrointestinal stromal tumors, epithelioid angiosarcoma, rhabdoid tumors, osteosarcomas, and primitive neuroectodermal tumors, to name a few. The detailed immunophenotypic properties of those lesions are provided elsewhere in this book. However, none of them manifests reactivity for gplOO-related melanocytic markers or tyrosinase, making those markers essential to the differential diagnostic process. 

The ambiguous histological differentiation and the controversial immunophenotype of synovial sarcoma make the microscopic diagnosis difficult, especially when the tumor occurs in atypical locations or when the tumor reveals a non-specific immunohistochemical phenotype, which may resemble the immunophenotypic profile of other malignancies such as different types of sarcoma (solitary fibrous tumor, malignant peripheral nerve sheet tumor, fibrosarcoma, epithelioid sarcoma or leiomyosarcoma), metaplastic carcinoma and mesothelioma. Since synovial sarcoma reveals a different clinical behavior than the other mentioned tumors, it is important to discriminate it from these malignancies and additional methods that are more specific may be necessary to confirm the diagnosis. 

---