Clinicopathologic characteristics and molecular subtypes of invasive papillary carcinoma of the breast: a large case study.

Purpose: Although patients with invasive papillary carcinoma (IPC) often have favorable prognoses, it remains unclear whether this special type of breast cancer represents a distinct morphological entity with its own biological features and clinical behavior distinct from those of invasive ductal carcinoma (IDC) and whether its four molecular subtypes are associated with different prognoses.

Methods: The study is a retrospective analysis of a large patient cohort from a single institution. 284 IPC samples were collected from January 2000 to May 2011. 300 IDC cases were selected randomly from 13,428 cases of IDC during the same periods. We assessed the clinicopathologic characteristics, molecular features, and prognostic value of IPC (n = 284) and compared them to those of IDC (n = 300). Clinicopathologic features and survival status of the four subtypes of IPC were also evaluated.

Results: IPC differed from IDC with respect to age upon diagnosis, tumor grade, lymph node status, and menopausal status (P < 0.05). IPC was associated with a better 5-year overall survival rate (OS) (92.77 vs. 87.95 %) and disease-free survival rate (DFS) (87.95 vs. 80.72 %) than IDC. Tumors of the luminal A subtype had a better 5-year OS (97.78 %) and DFS (95.56 %) than other subtypes.

Conclusions: The biologic behavior of IPC is more favorable to patient outcome than that of IDC. The chance of pure IPC causing death without an intervening event of a different histologic type is exceptionally low. Luminal A subtypes have better outcomes when compared to the other subtypes.