Large axillary galactocele mimicking a soft-tissue tumor in accessory breast tissue: a rare clinical entity.

Introduction and importance: Accessory breast tissue is a developmental anomaly that may be subject to the same hormonal influences as normal breast tissue. A galactocele, a benign milk-retention cyst, typically affects lactating women but is exceedingly rare in axillary accessory breast tissue. Because an axillary galactocele can mimic lymphadenopathy, lipoma, or malignancy, it often poses a diagnostic challenge. Case presentation: A 33-year-old multiparous lactating woman presented with a progressively enlarging right axillary swelling that had become mildly painful over time. Examination revealed a large, well-defined cystic mass in the right axilla, with normal bilateral breasts and contralateral axilla. Ultrasound demonstrated a cystic lesion with internal echoes suggestive of a galactocele. Fine-needle aspiration produced thick, milk-like fluid, confirming the diagnosis. Surgical excision of the cyst and associated accessory breast tissue was performed due to its size, symptoms, and the patient's preference. Recovery was uneventful, breastfeeding was preserved, and no recurrence was observed. Clinical discussion: A galactocele arising within axillary accessory breast tissue is exceptionally rare and may be misdiagnosed as lymphadenopathy, lipoma, abscess, or malignancy. Targeted imaging and aspiration are key to distinguishing it from other axillary pathologies. While conservative management may suffice in small or asymptomatic cases, surgical excision provides definitive treatment and prevents recurrence in large, symptomatic, or cosmetically concerning lesions. Conclusion: Axillary accessory breast tissue galactocele is an uncommon but important differential diagnosis in lactating women presenting with axillary masses. Prompt recognition through clinical assessment, ultrasound, and aspiration facilitates accurate diagnosis. Surgical excision remains an effective management option for symptomatic cases, ensuring excellent outcomes.