OBJECTIVETo elucidate the clinicopathologic features, immunophenotype and differential diagnosis of intracystic papillary carcinoma (IPC).

METHODSThe clinical and pathological characteristics of 14 cases of breast IPC were studied. Immunohistochemical study of SMA, MSA, ER, PR, p63, AE1/AE3, 34betaE12 and CK5/6 was performed using Envision method.

RESULTSThe age of IPC patients ranged from 42 to 79, with a mean age of 65.4 years. A palpable mass was the most common symptom. There were two morphological features: (1) Slender papillae lined by tall columnar epithelial cells which were present directly on the fibrovascular cores without an intervening myoepithelial cell layer (9 cases). (2) The proliferation may assume a cribriform architecture with rigid, punched-out regular spaces or a solid glandular pattern, studded with fibrovascular cores (5 cases). Low nuclear grade is typically seen. Among the 14 cases of IPC, 11 were of pure type. Ductal carcinoma in situ (DCIS) in adjacent ducts was found in one case, and invasive carcinoma was found in two cases. Immunohistochemical results showed that the tumor cells were homogenously strongly positive for ER and PR, but were negative or focally and weakly positive for CK5/6 and 34betaE12. Myoepithelial cell staining was negative within the tumor; and was diminished or scattered at the periphery of the tumor.

CONCLUSIONSIPC is a rare entity that usually arises in older women. It is specific enough in its clinical presentation and morphologic appearance to warrant distinction from other breast lesions.