Recurrent bilateral giant breast fibroadenomas with a somatic PIK3CA p.G106V mutation: case report and review of current evidence

Fibroadenomas are common benign breast tumors, but recurrent bilateral giant fibroadenomas are rare. Recent studies suggest genetic factors, such as PIK3CA mutations, may influence tumor behavior. A 23-year-old woman with prior multiple fibroadenoma excisions presented with progressively enlarging bilateral breast masses and marked deformity. Imaging revealed multiple well-circumscribed lesions, the largest measuring 7.5 cm. Serum prolactin was elevated; estradiol and progesterone were normal. She underwent bilateral excision with reduction mammoplasty and nipple–areolar reconstruction. Histology confirmed fibroadenomas with epithelial hyperplasia; immunohistochemistry showed diffuse estrogen receptor positivity (>90% of cells) and a Ki-67 index of 5–10%. Next-generation sequencing detected a somatic PIK3CAc.317G>T (p.G106V) mutation. Integration of histological, hormonal, and molecular findings can guide individualized management of recurrent fibroadenomas. Large-scale studies are required to assess the prognostic significance of PIK3CA mutations in benign breast tumors.