Abstract
BACKGROUND: According to previous studies, tall cell carcinoma with reversed polarity can be easily distinguished from ductal carcinoma in situ based on the absence of myoepithelium and a typical histologic feature. However, to the best of our knowledge, no cases of papillary ductal carcinoma exhibiting tall cell and reversed polarity features with intact myoepithelium have been reported, and thus its diagnosis and prognosis remain unclear. CASE PRESENTATION: A 54-year-old female with a palpable lump in her right breast for 3 years. There were no other symptoms found. A preoperative ultrasound examination showed an oval, well-circumscribed, anechoic cystic appearance with hypoechoic adnexal nodules, classified as 3-4a in the Breast Imaging Reporting Data System. Surgical excision revealed an in-situ breast carcinoma exhibiting a solid papillary pattern and tall cell with reversed polarity of nuclei. After thorough postoperative pathology, immunohistochemistry, and next-generation sequencing, we hypothesized that it might be a new ductal carcinoma in situ subtype with tall cells and reversed polarity of the mammary gland. CONCLUSIONS: We herein present a rare case of papillary ductal carcinoma in situ with tall cell and reversed polarity morphology breast cancer, which can closely mimic tall cell carcinoma with reversed polarity and ductal carcinoma in situ. Thorough evaluations of histologic features, immunohistochemistry results, and genetic alterations are significant in identifying this rare entity. In addition, this type of breast cancer is low-malignant and has a favorable prognosis without any adjuvant therapy after complete resection.