Imaging of a Mucocele-Like Lesion of the Breast: A Case Report and Literature Review

Mucocele-like lesions (MLLs) of the breast are rare mucin-producing lesions that can closely mimic malignant mucinous neoplasms on imaging and histopathology. We present the case of a 61-year-old woman with a non-palpable MLL of the left breast detected on screening mammography. Mammography demonstrated a 10 mm asymmetry visible on a single mediolateral oblique view in the upper outer quadrant of the left breast, without associated microcalcifications. Targeted ultrasonography did not demonstrate a definitive correlate corresponding to the mammographic finding. Stereotactic core needle biopsy revealed abundant extracellular mucin without malignant cells, raising a differential diagnosis that included a benign MLL versus invasive mucinous carcinoma. Surgical excision confirmed a benign MLL with acellular mucin and focal atypical ductal hyperplasia in adjacent tissue. This case highlights the imaging variability of MLLs and underscores the importance of surgical excision for definitive diagnosis and exclusion of concurrent malignancy.