A 79-year-old woman presented with a palpable left breast mass. Mammogram confirmed a well-circumscribed nodule within the breast corresponding to the palpable abnormality. She underwent a biopsy and a subsequent partial mastectomy.
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The occurrence of primary breast neoplasms with eccrine and apocrine phenotypes has been described and supports the notion that breast is a modified sweat gland. One of those entities is a cylindroma, which is a benign often dermal-based neoplasm that is most commonly encountered on the neck, head, and scalp of middle-aged and elderly females. These tumors are uncommon in the breast. Both breast and dermal cylindromas share histomorphologic and immunohistochemical features. These tumors are nonencapsulated but well-demarcated lesions that show a characteristic “jigsaw” pattern of epithelial nests. The epithelial nests are composed of central luminal cells and peripheral myoepithelial cells. Mitotic activity is generally absent and nuclear pleomorphism is minimal. The nests of cells are surrounded by a thickened band of basement membrane material. Globules of hyaline basement membrane material may be present in the interior of the epithelial nests. The epithelial cells are immunoreactive with markers typically expected to be positive in ductal epithelium of the breast, including GATA3 and CK7, whereas the peripheral cells show positivity with myoepithelial cell markers such as p63. Cylindromas may show aberrant MYB-NFIB fusion transcripts.
Breast cylindromas show overlapping features and marker positivity with other entities such as adenoid cystic carcinomas and basaloid invasive ductal carcinomas; therefore, correlations with clinical presentation, imaging studies, patient history, and careful microscopic evaluation are of utmost importance to arrive at accurate diagnoses.
Patricija Zot, M.D.
Fellow, Surgical Pathology
Charles Sturgis, M.D.
Consultant, Anatomic Pathology
Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine and Science