Accessory mammary gland is an uncommon lesion, which occurs in 0.4%–6% of women. It is mostly located in the axilla of both sides, but when it presents unilateral large in size and sessile, it can cause difficulty in clinical diagnosis, which mimics lipoma or adipose tissue lesion, usually, it is bilateral and presents asymptomatic lump in the axilla during pregnancy and lactational period. Anxiety is the major cause of concern, as the general population are not aware of accessory breast. Histopathological diagnosis is very important as axillary mass or breast tissue may undergo changes like mastitis, fibrocystic disease, and rarely carcinoma. We present an axillary mass on the left side in 24-year-old female, which has been diagnosed with accessory mammary gland on fine-needle aspiration cytology study, which was mimicking sessile lipoma as a rare clinical presentation.