Nuclear factor XIIIa staining (clone AC‐1A1 mouse monoclonal) is a sensitive and specific marker to discriminate sebaceous proliferations from other cutaneous clear cell neoplasms

Sebaceous carcinoma is a rare but serious malignancy that may be difficult to diagnose when poorly differentiated. Other epithelial tumors with clear cell change may mimic sebaceous carcinoma. Few useful or specific immunohistochemical markers for sebaceous differentiation are available. Nuclear staining with factor XIIIa (clone AC‐1A1) was recently found to be a highly sensitive marker of sebaceous differentiation. We evaluated nuclear factor XIIIa (AC‐1A1) staining in sebaceous neoplasms vs. other cutaneous clear cell tumors. We stained 27 sebaceous proliferations: sebaceous hyperplasia (7), sebaceous adenoma (8), sebaceoma (5), sebaceous carcinoma (7). We also stained 67 tumors with clear cell change: basal cell carcinoma (8), squamous cell carcinoma (8), hidradenoma (7), desmoplastic trichilemmoma (2), trichilemmoma (10), trichilemmal carcinoma (3), clear cell acanthoma (9), atypical fibroxanthoma (1), syringoma (8), trichoepithelioma (1), metastatic renal cell carcinoma (2), and nevi with balloon cell change (8). Nuclear factor XIIIa (AC‐1A1) staining was present in 100% of sebaceous proliferations; 96% displayed strong staining. Non‐sebaceous clear cell tumors were negative or only weakly positive with factor XIIIa (AC‐1A1) in 95.5%; only 4.5% showed strong staining. This suggests that strong nuclear factor XIIIa (AC‐1A1) staining is a sensitive and specific marker of sebaceous neoplasms vs. other clear cell tumors.