[Solid Papillary Carcinoma of the Breast-A Case Treated with Total Mastectomy Following Preoperative Diagnosis of Mass-Forming Ductal Carcinoma].

Solid papillary carcinoma(SPC)is a newly recognized disease entity that was incorporated into the WHO classification in 2012. It is rare and less than 1% of all breast cancers, that is the reason of no stand treatment protocol. Here, we report a case of SPC encountered at our institution. The patient was a 47-year-old woman who presented with a progressively enlarging mass in the right breast. The tumor was detected as a solid mass with well-defined margins, approximately 5 cm in maximum diameter on imaging examination. Although neoadjuvant chemotherapy was considered due to the large tumor size, no definitive evidence of invasion was found on preoperative evaluation, and upfront surgery was selected. She underwent right total mastectomy and sentinel lymph node biopsy. Histopathological examination revealed solid cellular proliferation with fibrovascular cores, large nest formation, partial comedo necrosis, and a 2 mm focus of invasion, leading to a diagnosis of SPC with invasion. Immunohistochemical staining of the invasive component showed ER-positive, PgR-positive, HER2 score 2+(DISH non-amplified), Ki-67 index 6%, and synaptophysin-positive, suggesting a Luminal-type SPC with invasion. Postoperatively, the patient was started on tamoxifen, and she remains recurrence-free to date. This case underscoring the importance of careful pre-treatment assessment of malignancy.