Immunolabeling pattern of cytokeratin 19 expression may distinguish sebaceous tumors from basal cell carcinomas

Background:  Distinction between sebaceous tumors and basal cell carcinomas can often pose diagnostic problems. Recent work with the antibody to cytokeratin 19 (CK 19) has shown that this marker has high specificity for undifferentiated basaloid cells. Our aim was to evaluate the use of CK 19 staining patterns in differentiating between sebaceous tumors and basal cell carcinomas. The sebaceous tumors that were examined in this study included sebaceous adenomas, sebaceous epitheliomas (sebaceomas) and sebaceous carcinomas. Methods:  Thirty‐seven cases including 5 sebaceous adenomas, 16 sebaceous epitheliomas, 6 sebaceous carcinomas and 14 basal cell carcinomas (7 being of the morpheaform type and 7 nodular basal cell carcinomas) were tested with a monoclonal mouse antibody to human CK 19. Results:  CK 19 was focally positive in 1/5 (20%) sebaceous adenomas, 8/16 (50%) of sebaceous epitheliomas and 1/6 (17%) of sebaceous carcinomas. Strongly positive expression of CK 19 was not seen in any of the sebaceous adenoma, sebaceous epithelioma or sebaceous carcinoma specimens. CK 19 was found to be strongly positive in 9/14 (64%) and focally positive in 2/14 (14%) of basal cell carcinomas. Conclusion:  CK 19 expression can be helpful in differentiating sebaceous tumors (including sebaceous adenomas, sebaceous epitheliomas and sebaceous carcinomas) from basal cell carcinomas and may be a useful adjunct when these entities are included in the differential diagnosis.