Fibroma of the breast: a rare tumour in the spectrum of the benign spindle cell tumours of the mammary stroma.

Benign spindle cell tumours of the mammary stroma comprises different lesions that show a variable degree of fibroblastic/myofibroblastic differentiation. We herein report a previously under-recognised hypocellular fibrocollagenous tumour of the breast, for which the term "fibroma" is proposed. The tumour was composed of CD34-positive bland-looking spindle cells embedded in an abundant hyalinised stroma. Fluorescence in situ hybridisation (FISH) showed 13q14 deletion in most neoplastic cells, a chromosomal alteration typically found in mammary myofibroblastoma. Based on morphological, immunohistochemical, and cytogenetic features, we suggest that fibroma belongs to the group of the benign spindle cell tumours of the mammary stroma.