Diagnostic dilemma of micropapillary variant of mucinous breast cancer

An elderly woman presented with an enlarging left breast lump. Breast imaging revealed a large suspicious mass associated with cystic components. Core biopsy however was non-diagnostic and only revealed necrotic papillary tissue. The patient then underwent excision of the lesion that revealed a large area of intracystic papillary ductal carcinoma in situ with a focus of micropapillary variant of mucinous cancer. This case describes how this rare subtype could present as necrotic papillary tissue on core biopsy, resulting in a diagnostic dilemma, which had not been previously reported. A literature review of this rare subtype was performed too.