Intracystic (encysted) papillary carcinoma of the breast: a clinical, pathological, and immunohistochemical study.

Intracystic papillary carcinoma (IPC) of the breast is a rare tumor with predilection for elderly women and distinctive pathological features that must be distinguished from ductal carcinoma in situ (DCIS) of papillary type and from invasive papillary carcinoma. The clinical, radiological, and pathological features of 29 cases of IPC are reported. The cases were divided into three groups (IPC alone, associated with DCIS, or associated with invasive carcinoma) and studied in terms of their size, predominant architectural pattern, nuclear grade, and presence of necrosis. Immunohistochemical studies were performed to evaluate the c-erbB2 oncoprotein, estrogen receptors, and ki-67 antigen expression. The median age of the patients was 75 years. Microscopically, nine tumors (31.0%) were IPC alone, nine (31.0%) had IPC associated with DCIS, and 11 (38.0%) were IPC associated with invasive carcinoma. Most of the IPC cases had low or intermediate nuclear grade, no necrosis, strongly expressed estrogen receptor, and was negative for c-erbB-2. Nuclear grade 3 and necrosis were found only in cases of IPC associated with invasive carcinoma. The median Ki-67 antigen expression was 10.6%. One patient with IPC alone had a recurrence 5 years later. Lymph node metastases were found in one patient who had the tumor with the biggest invasive area. IPC is a low-grade carcinoma with overall good prognosis. However, there is a high frequency of DCIS or invasive carcinoma associated with it, and the prognosis of these cases is related to the type, grade, and size of the associated lesions.