Pathologic Findings from the National Surgical Adjuvant Breast Project (Protocol No. 4): VI. Invasive Papillary Cancer

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Abstract
Although papillary forms of intraductal cancer are a common component of many mammary cancers, invasive papillary cancer of the breast is relatively rare. Only 35 examples were encountered in the specimens obtained from 1603 women participating in a prospective randomized study of invasive mammary cancer. Contingency-table analysis disclosed that invasive papillary cancer, as opposed to the nonpapillary histologic types, is significantly more likely to show circumscription, cytoplasmic oxyphilia, microcalcification, intermediate histologic grade, moderate or marked mucin and an intraductal component of papillary type. Although patients who have invasive papillary cancer are frequently judged by clinical criteria to have regional nodal metastases, in pathologic analysis these metastases are not commonly found and, if present, involve fewer than four nodes. There is a significant frequency of marked sinus histiocytosis in regional nodes. The lesion occurs with a significantly high frequency among non-Caucasian and postmenopausal women. Only three patients with invasive papillary cancer experienced treatment failure after five years of observation. Life-table probabilities showed that the treatment failure rate was significantly lower for the group of patients who had invasive papillary cancer than for the group who had any other histologic type, and in this regard invasive papillary cancer was similar to the tubular and mucinous varieties. Although apocrine metaplasia, fibrous supporting stalks and cellular differentiation have been espoused as important criteria distinguishing intraductal papilloma from intraductal cancer, these features were also not uncommonly observed in the examples of invasive papillary cancer studied. It is concluded that invasive papillary cancer represents a unique histologic type of invasive mammary cancer attendant with a favorable prognosis.