Ectopic breast tissue presenting as an enlarging abdominal mass.

Ectopic breast tissue (EBT) is an uncommon entity that occurs in about 6% of the population, more frequently in Asian people. It manifests as a nonspecific soft tissue mass that can develop in any location along the "milk-line," with the axilla being the most frequently reported location. As with normal breast tissue, both benign and malignant processes can arise from EBT. Therefore, imaging plays an important role in the adequate assessment of these soft tissue lesions, characterizing its shape, borders, internal components, and vascularity, as well as its relationship with the deep fascia and adjacent structures. Here we present a case of a 33-year-old female Indian patient with an 8 cm soft tissue mass in the upper left abdominal quadrant with a recent increase in size. Clinical and imagiological evaluation were nonspecific but established the nonaggressive behavior of the lesion. To ultimately exclude malignancy, an ultrasound-guided biopsy was performed providing the histological diagnosis of EBT. This case report illustrates the value of clinical, radiological, and histological correlation in the approach of indeterminate soft-tissue tumors, with special focus on lesions in close proximity to the native breasts, where EBT should not be forgotten amongst differentials.