Radiologically malignant but histologically benign: clear cell hidradenoma of the breast

Clear cell hidradenoma (CCH) of the breast is a rare benign adnexal tumour that can radiologically mimic breast malignancy, risking overtreatment. A woman in her 70s presented with a palpable 3-cm left breast mass. Mammography and ultrasound showed a well-defined heterogeneous mass, suspicious of malignancy. Core biopsy demonstrated epithelial proliferation with squamous differentiation (B3 without atypia), but findings were inconclusive. Histopathology and immunohistochemistry (IHC) findings on wide local excision confirmed CCH, characterised by clear cells with squamous metaplasia, mucinous differentiation and focal apocrine change. Although benign, narrow excision margins and uncertain recurrence risk prompted annual mammographic surveillance for 5 years following multidisciplinary team (MDT) consensus. This case emphasises the diagnostic challenge of rare benign lesions, which may have imaging features indistinguishable from breast carcinoma. Radiological–pathological discordance warrants diagnostic reassessment. In this case, definitive diagnosis required surgical excision with histopathological and IHC evaluation, alongside MDT discussion to avoid unnecessary oncological management.