Giant Lipoma of the Arm Masquerading as an Accessory Breast: A Report of a Rare Case.

Accessory breast is an extremely rare condition that develops in 0.4%-6% of females. It is primarily found in the axilla and is frequently misdiagnosed. It is usually bilateral and manifests during pregnancy or lactation as an asymptomatic tumor. The diagnosis of ectopic breast tissue is crucial because it is capable of undergoing the same pathological changes as normal breast tissue, including mastitis, fibrocystic changes of the breast tissue, and, in extreme cases, even malignancy. We present the case of a 40-year-old female who presented with swelling in the left upper arm for the past eight years, which was associated with pain. Initially, accessory breast was kept as the clinical diagnosis. However, further imaging and histological analysis revealed it to be a giant lipoma of the upper arm.