Myofibroblastoma of the breast in a 5-year-old girl: A case report.

RATIONALE: Myofibroblastoma is a rare, benign spindle cell tumor originating from the breast stroma. Although it predominantly affects older men and occasionally postmenopausal women, its occurrence in children is exceedingly rare.

PATIENT CONCERNS: A 5-year-old girl presented with a palpable mass on the lateral aspect of her left breast.

DIAGNOSES: Serial ultrasound examinations were conducted every 6 months for 1 year because the lesion was initially suspected to be a lipoma or an enlarged lymph node.

INTERVENTIONS: Owing to progressive enlargement of the mass to 3 cm, surgical excision was performed. A well-defined yellow-white solid mass located in the subcutaneous layer was completely removed.

OUTCOMES: The histopathological and immunohistochemical findings confirmed the diagnosis of a myofibroblastoma. The postoperative course was uneventful, and no recurrence has been reported to date.

LESSONS: Although extremely rare, myofibroblastoma should be considered in the differential diagnosis of enlarged breast masses in children. Complete surgical excision is the treatment of choice, and regular follow-up is recommended.