Nevus lipomatosus superficialis mimicking ectopic breast tissue: A rare case report.

Rationale: Diagnosis of solitary superficial lipomatous mass may vary depending on circumstances. Although preliminary diagnosis can be made through clinical symptoms and imaging studies, final diagnosis can change through histological examination. This is the first reported case of nevus lipomatosus superficialis (NLS) resembling ectopic breast tissue which may provide valuable insights for clinicians managing similar lesions.

Patient Concerns: A 41-year-old female had a solitary mass on her left lower flank, lasting more than 10 years with cyclic pain corresponding to her menstrual cycle.

Diagnoses: A computed tomography scan suggested benign subcutaneous lipoma, but histopathological examination after surgery confirmed the diagnosis of NLS.

Interventions: Surgical excision was performed without complications.

Outcomes: No regrowth of the lipomatous mass was observed at the 6-month follow-up, and there was no recurrence of cyclic pain.

Lessons: This report aims to discuss an unusual presentation of NLS that mimics ectopic breast tissue and causes cyclic pain related to the menstrual cycle. Understanding this case provides insights into the potential hormonal influence on focal adipose tumors and the challenges in differential diagnosis.