A rare case of TLE1-positive sclerosing epithelioid fibrosarcoma expanding the differential diagnosis of TLE1-positive tumors: a case report.

Transducin-like enhancer of split 1 (TLE1) is a transcription factor known for its strong overexpression and immunopositivity in synovial sarcoma. Several studies have revealed that its immunopositivity is not always specific to synovial sarcoma, with several cases showing positivity in peripheral nerve sheath tumors and solitary fibrous tumors. Occasional weak staining for TLE1 has also been described in clear cell sarcoma, high-grade chondrosarcoma, Ewing sarcoma, rhabdomyosarcoma, GIST, myxofibrosarcoma, and leiomyosarcoma. Here we present the first unique case of sclerosing epithelioid fibrosarcoma with strong, diffuse TLE1 positivity, resulting in a new consideration for the differential diagnosis of TLE1 positivity.