[533] Mismatch Repair Protein Immunohistochemistry in Sebaceous Lesions

Elizabeth Plocharczyk, Heather Hampel, Wendy Frankel, Sara Peters. Ohio State University, Columbus, OH

Background: The association between Lynch syndrome and sebaceous neoplasms is well-characterized. Absence of expression of mismatch repair proteins (MMRP) by immunohistochemistry is often used in other Lynch-associated tumors such as colon and endometrial carcinomas to guide testing for this disorder.
Design: Immunohistochemical staining for the MMRP MLH1, PMS2, MSH2, and MSH6 was performed on 36 sebaceous neoplasms and 7 cases of sebaceous hyperplasia and presence or absence of staining was assessed. Additionally, number of tumor-infiltrating lymphocytes per high-powered field (TIL) was counted using the H&E stained slide, averaged over 5-10 high-powered fields. Medical records were also reviewed.
Results: The composition of the 43 sebaceous lesions examined and their immunohistochemical profiles are summarized in Table 1.

MMRP expression in sebaceous lesions.
lesionMMRP present≥1 MMRP absenttotal
sebaceous carcinoma11415
sebaceous neoplasm3912
sebaceous adenoma516
sebaceous hyperplasia707

Of the neoplastic sebaceous lesions, 38.9% lacked expression of one or more MMRP. In 10 of the 14 lesions with absent MMRP expression, both MSH2 and MSH6 were absent. Three lacked MLH1 and PMS2 expression and one lesion lacked only MSH6. Of the 10 patients with absent MMRP expression, 2 had previously diagnosed Lynch syndrome, 3 had some combination of personal and/or family history of endometrial and/or colon carcinomas, 3 had no personal or family history suggestive of Lynch syndrome, and 2 had no recorded personal or family history. A total of two patients had multiple sebaceous lesions and both patients lacked expression of MSH2 and MSH6 in all lesions. One of those patients had a diagnosis of Lynch syndrome and the other had a family history of uterine cancer. TIL in patients with absent MMRP expression was statistically significantly greater than in patients with normal MMRP expression (16.5 vs. 9.7, p=0.027); see Figure 1.

Conclusions: Sebaceous lesions other than hyperplasia are rare entities that frequently lack MMRP expression. These neoplasms are commonly associated with Lynch syndrome and immunohistochemical screening for MMRP expression might help select for patients in whom genetic testing is indicated.
Category: Dermatopathology

Monday, March 19, 2012 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 80, Monday Morning


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