Granulomatous mastitis in accessory breast tissue: A rare presentation and surgical management.

Granulomatous mastitis (GM) in accessory breast tissue is rare. The present study aimed to report a rare case of GM in accessory breast tissue. A 39-year-old female patient presented with right axillary discomfort and swelling for ~5 days. On clinical examination, a tender, firm lump was detected in the right axillary region. The ultrasound showed diffuse parenchymal heterogeneity and surrounding edema in the right accessory breast associated with reactive axillary lymph nodes. Following unresponsiveness to conservative treatment, a surgical procedure was performed in the form of an excisional biopsy and the lesion was diagnosed as GM. During the six-month follow-up, there were no recurrences. The exact cause of GM remains uncertain and the etiology within accessory breast tissue is even less understood. Proposed mechanisms suggest that it may result from an exaggerated immune response triggered by various factors, such as infection, autoimmunity or hormonal fluctuations. GM in accessory breast tissue is a rare and challenging clinical condition to be diagnosed. Due to the rarity of this condition, it highlights the importance of including GM in the differential diagnosis of axillary masses.