Prevalence of Terminal Duct Lobular Units and Frequency of Neoplastic Involvement of the Nipple in Mastectomy.

Context.-Breast cancer treatment has greatly evolved from radical mastectomy to more cosmetically acceptable and less-debilitating surgeries. Nipple-sparing mastectomy is increasingly done for both cancer treatment and risk reduction. The frequency of terminal duct lobular units (TDLUs) and occult neoplastic epithelial proliferation in grossly/clinically unremarkable nipples (GUNs) is not well investigated. Objective.-To describe frequency of TDLUs and occult and overt neoplastic nipple involvement. Design.-Nipples from 105 consecutive specimens (90 therapeutic, 15 prophylactic) were studied. Sixty-five nipples were entirely submitted to evaluate frequency of TDLUs; the rest had 1 vertical section submitted. Results.-Terminal duct lobular unit was seen in 17 GUNs (26%). Six had TDLU in the base, 6 had it in the papilla, and 5 in both. Four GUNs showed lobular carcinoma in situ (1), Paget disease (1), and pagetoid extension of underlying malignancy (2). Grossly/clinically abnormal nipples had Paget disease (2), lymphovascular invasion (2), invasive carcinoma (4), and pagetoid extension (5). Involved nipples were closer to tumor (mean, 1.1 versus 3.2 cm, P < 001), had larger underlying tumors (mean, 4.3 versus 2.6 cm, P =.03) and of higher grade (P = .04), and more often had lymph node metastases (91% versus 44%, P = .007). No pathologic abnormalities were found in prophylactic mastectomy nipples. Conclusions.-Terminal duct lobular units were seen in 26% of nipples. They were frequently seen in the nipple papilla. Occult neoplastic epithelial proliferation was seen in 5% of grossly/clinically unremarkable therapeutic mastectomy nipples. Pagetoid extension was the dominant spread of underlying malignancy. Overall, the nipple was more often involved by larger and higher-grade tumors located closer to the nipple. All prophylactic mastectomies had unremarkable nipples. These findings should be considered while selecting patients for nipple-sparing mastectomy. [ABSTRACT FROM AUTHOR]