Subcutaneous contralateral upper limb metastasis in invasive breast ductal carcinoma: a rare presentation

Invasive ductal carcinoma of the breast is known to typically metastasise to the lungs, liver, bone and brain, with subcutaneous soft tissue involvement being rare, with only eight cases reported internationally. We report the case of a woman with a history of left-sided invasive ductal carcinoma treated with a mastectomy and adjuvant therapy, who presented 7 years later with a 2.8 cm subcutaneous lesion over the contralateral shoulder. Histopathological examination and immunohistochemistry confirmed metastatic invasive ductal carcinoma, displaying a morphological and receptor profile congruent with her primary tumour. This case highlights the potential for late and atypical metastatic presentations of breast cancer and underlines the importance of maintaining diagnostic vigilance in long-term survivors.