Sebaceous neoplasms with mismatch repair protein expressions and the frequency of co-existing visceral tumors.

BACKGROUND: Visceral malignancy has been associated with sebaceous neoplasms in patients with Muir-Torre syndrome. However, no large studies have been done to evaluate the frequency of visceral tumors in patients with sebaceous neoplasms and mismatch repair (MMR) protein expression of the sebaceous tumors.

OBJECTIVE: We sought to determine the frequency of visceral tumors in patients with sebaceous neoplasms, MMR protein expression of the sebaceous tumors, and the related surveillance practices of physicians.

METHODS: We identified 85 patients with sebaceous neoplasms. Relevant clinical information was obtained via chart review and database searches. MMR protein expression was examined by immunohistochemistry.

RESULTS: Nineteen of the 85 patients had a total of 22 visceral malignancies, of which 41% were genitourinary in origin. Ten of the 17 patients (59%) with visceral malignancy had loss of MMR expression in their sebaceous neoplasms or somatic MMR mutation. Thirty patients had other findings such as colonic adenomas and polyps. Of the 23 patients who had a family history of visceral malignancy, 9 had a personal history of visceral malignancy.

LIMITATIONS: Only one sebaceous tumor from each patient (except one) was tested for MMR, which might reduce the sensitivity.

CONCLUSION: Our findings demonstrate an increased frequency of internal malignancy in patients with sebaceous neoplasms compared with the general population, and highlight the heterogeneous nature of the visceral tumors. A majority of the sebaceous tumors show loss of MMR expression. The study reminds us to strive toward a consistent and comprehensive approach to screening for internal malignancy when a patient is given a diagnosis of a sebaceous neoplasm.