A Mystery in the Male Breast: Immunomorphological Confirmation of Invasive Papillary Carcinoma in an Elderly.

Male invasive papillary carcinoma (IPC) of the breast is an uncommon malignancy, accounting for a small proportion of male breast cancers, and poses significant diagnostic challenges because of its rarity and morphological overlap with other papillary lesions. We report the case of an 85-year-old man who presented with a recurrent painless right breast mass following previous excision without histological evaluation. He underwent simple mastectomy with sentinel lymph node biopsy. Histopathological examination demonstrated an invasive papillary carcinoma comprising over 90% papillary architecture, absence of a myoepithelial layer, and Nottingham Grade 2 morphology. Immunohistochemistry showed diffuse estrogen receptor and progesterone receptor positivity with negative HER2-neu expression, confirming a luminal A molecular subtype. The sentinel lymph node was free of metastasis. The patient received adjuvant tamoxifen and chemotherapy and remains under follow-up. This case highlights the importance of meticulous histomorphological assessment complemented by immunohistochemistry in establishing the diagnosis and guiding management of this rare male breast malignancy, particularly in resource-limited settings.