Metastatic potential of encapsulated (intracystic) papillary carcinoma of the breast: a report of 2 cases with axillary lymph node micrometastases.

Intracystic papillary carcinoma of the breast has rarely been reported to be associated with metastases. Presented are 2 cases, both of which showed micrometastatic carcinoma in axillary lymph nodes; neither demonstrated stromal invasion. Nearly complete absence of a myoepithelial cell layer around the periphery of the lesions was noted. One case showed 3 separate foci of micrometastatic carcinoma in 1 of 3 sentinel lymph nodes; the second showed micrometastases in 2 of 11 axillary lymph nodes. The clinical significance of micrometastases in lymph nodes associated with intracystic papillary carcinoma is unknown. The term encapsulated papillary carcinoma has been proposed to name papillary carcinomas that are surrounded by a fibrous rim, but which show a scant or absent myoepithelial cell component. The current 2 cases offer evidence to support the use of this term for particularly large encysted lesions. Sentinel lymph node biopsy may be prudent in such cases.