Cystic Hypersecretory Carcinoma of the Breast: A Rare Case Report with Review of Literature and Emphasis on Differential Diagnosis.

Karthik DhandapanCystic hypersecretory carcinoma (CHC) is a rare subset of in-situ breast carcinoma with or without associated invasive carcinoma. It is part of a spectrum of cystic hypersecretory lesions that includes cystic hypersecretory hyperplasia (CHH), CHH with atypia, CHC in situ, and CHC with invasion. Only 20 cases of CHC with invasion have been reported so far. A 60-year-old female presented with a palpable right breast mass. A core needle biopsy was carried out, which was reported as invasive breast carcinoma with areas of ductal carcinoma in situ (DCIS). Modified radical mastectomy was done post-neo-adjuvant chemotherapy; On microscopy, dilated cystic spaces filled with eosinophilic secretions (thyroid colloid-like), lining neoplastic cells with variable degrees of proliferation and atypia were seen. There were multiple foci of invasion; both skin invasion and axillary lymph node metastasis were present. Immunohistochemistry (IHC) was done with relevant markers; correlating all these findings, a diagnosis of CHC with invasion was made. CHC is a distinct form of DCIS with or without associated invasion. Awareness of this entity is required to rule out other differential diagnoses and to avoid misinterpretation. Little is known about the IHC profile, biological behavior, prognosis, and molecular profile of CHC due to its rarity.