Fibrocystic disease within an axillary accessory breast (Kajava class IV): a case report

Accessory breast tissue is a congenital anomaly occurring in 0.4-6% of the population, most commonly in the axilla. While this tissue is subject to the same physiological and pathological changes as orthotopic breast tissue, fibrocystic disease presenting as a large axillary mass is rare, representing a diagnostic challenge that mimics lipomas and other conditions common in the axillary region.

We report a case of 33-year-old female who presented with a chronic painful mass in the left axilla that have been present for 10 years. Clinical examination revealed a soft, mobile mass without associated nipple or areola (Kajava Class IV). Initially suspected to be a lipoma, ultrasonography suggested ectopic breast tissue. Excisional biopsy was performed, revealing a mass of size 9 × 8.5 x 3.5 cm. Histopathological analysis confirmed benign mammary parenchyma with prominent fibrocystic changes, including ductal ectasia and apocrine metaplasia. The patient showed satisfactory recovery with no recurrence at the 1-month follow-up.

This case emphasizes the importance of including accessory breast tissue in the differential diagnosis of axillary swellings, even when clinical features suggest more common benign lesions like lipomas.

Early recognition through clinical suspicion, imaging, and histopathological confirmation is crucial, particularly in low-resource settings, to ensure appropriate management and monitor for potential neoplastic transformation.