Frequent TLE1 Expression in Cutaneous Neoplasms.

TLE1 immunohistochemistry is widely used as a biomarker for synovial sarcoma. Recently, we identified TLE1 expression in a subset of melanomas and noted staining in sebaceous glands and follicular epithelium. TLE1 immunohistochemistry has not been well studied in cutaneous tumors. The aim was to investigate TLE1 expression in sebaceous neoplasms, basal cell carcinoma (BCC), and squamous cell carcinoma (SCC) to determine whether the staining patterns may aid in the diagnosis or classification of these neoplasms. TLE1 immunohistochemistry was performed on sebaceous adenoma (n = 26), sebaceoma (n = 10), sebaceous carcinoma (n = 19), BCC (n = 20), and SCC (n = 19). Positivity was defined as dark-brown nuclear staining and graded as 3+ (strong staining of >50% of cells at 4×), 2+ (moderate staining of 10-50% of cells at 4× or >50% of cells staining at 10×), and 1+ (weak staining of <50% of cells at 10×). No staining was scored as 0. A score of 2-3+ was considered positive and 0-1+ negative. Nuclear TLE1 expression was identified in 25/26 (96%) sebaceous adenomas, 8/10 (80%) sebaceomas, and 17/19 (90%) sebaceous carcinomas. TLE1 also labeled 19/20 (95%) BCCs and 12/19 (63%) SCCs. TLE1 immunohistochemistry frequently highlights sebaceous neoplasms, BCC, and SCC with a fairly high sensitivity (63%-96%). Therefore, TLE1 is not a specific biomarker for synovial sarcoma and should be evaluated with caution, particularly in cases in which the differential diagnosis may include other cutaneous tumors. In addition, TLE1 does not seem to be useful in the diagnosis or classification of these neoplasms.