[Primary sebaceous carcinoma of the breast; three casuistic reports].

Objective: Presentation of three cases of primary sebaceous carcinoma of the breast particularly focusing on the clinical, biological and molecular genetic aspects regarding their possible pathogenetic relationship to the Muir-Torre and Lynch syndrome. Reviewed are basic principles of miscosatellite instability and dysregulations of mismatch repair genes by these inherited tumorous syndromes especially looking for morphologic and fenotypic parallels between sebaceous carcinomas of the breast and their cutaneous counterparts.
Design: Three casuistic reports.
Setting: Biopsy Lab s.r.o. and Sikl's Department of Pathology, Charles University and Faculty Hospital, Pilsen.
Methods: Three casuistic reports are covered in detail including broad immunohistochemistry (LSAB+, Dako).
Results: In three women aged 51 to 69 was diagnosed primary sebaceous carcinoma of the breast with maximum dimension ranged from 13 to 41 mm. Lumpectomy was performed at the smallest one and included sentinel lymph node examination turned out to be negative. The other two patients underwent modified mastectomy with axillary lymph node dissection. In tumor sized 25 mm, macrometastasis 4 mm in maximum dimension was identified in one axillary lymph node. Follow-up available in two women, both without regional metastasis, revealed no local or distant progression of the disease. The histology consisted of conventional G1-2 invasive duct carcinoma in all cases and sebaceous differentiation represented 10-40% of all neoplastic population. The patognomic features included cells with ample eosinophilic/clear foamy cytoplasm, partly with multiple crowded small vacuoles characteristically impressing the nuclei. All tumors were ER positive and Her2/neu 2+ lesion was not amplified. Strong diffuse nuclear expression of MLH1, PMS2, MSH2, MSH6 proteins in all cases confirmed unaltered mismatch repair genes pathway. Familial tumorous stigmas were not evident and subsequent close clinical monitoring in two of the patients tracked down no intern malignancy, including cutaneous sebaceous lesion.