Breast cylindroma: A rare and unexpected diagnosis

Cylindroma is a benign adnexal tumor histologically characterized by clusters of small basaloid cells arranged in a pattern resembling a jigsaw puzzle. Breast cylindromas are extremely rare with approximately 20 reported cases throughout literature. We present a case of a 71-year-old female with a slow growing cystic breast mass, originally identified 8 years prior to biopsy. Mammography and ultrasound demonstrated features of a simple cyst with circumscribed margins and anechoic internal echogenicity, respectively. Biopsy was performed due to increase in size, revealing the pathologic entity of cylindroma. The patient ultimately underwent surgical excision, which confirmed the diagnosis. We discuss the radiology, pathology and clinical course of breast cylindroma.