Metachronous bilateral invasive breast carcinoma with low-grade adenosquamous carcinoma on one side: A case report and literature review

Low-grade adenosquamous carcinoma (LGASC) is a rare variant of metaplastic breast carcinoma that consists of glandular and squamous elements in a spindle cell background. They lack distinctive imaging features and overlap with other breast neoplasm characteristics, posing a diagnostic challenge. We present the case of a 60-year-old woman with metachronous bilateral invasive breast carcinoma (MBBC). The mastectomy specimens of her left breast carcinoma revealed nests of squamous- appearing cells and “comma” glandular structures on a microscopic level. Comprehensive immunohistochemical examination of ER, PR, Her-2, p63, and CK7 CK5/6 confirmed the diagnosis of LGASC. Unlike other invasive breast carcinomas, LGASC have an indolent course and favorable prognosis. Eight years after surgery, she was diagnosed with a non-specific type of invasive breast carcinoma of the right breast via imaging, core needle biopsy and immunohistochemistry. This was a rare case of MBBC that has not been previously reported. Therefore, we report and review the relevant literature to raise awareness of this disease.