Pathologic findings from the National Surgical Adjuvant Breast and Bowel Project

BACKGROUND: The current report represents a 12-year clinicopathologic update of an earlier 5-year analysis of 180 patients with lobular carcinoma in situ (LCIS) who were treated with local excision and subsequent surveillance only. METHODS: Nineteen pathologic characteristics of LCIS were assessed as potential predictors of invasive and noninvasive ipsilateral breast tumor recurrence (IBTR) and contralateral breast tumor recurrence (CBTR) as well as mortality. RESULTS: Overall, only 26 IBTRs (14.4%) and 14 CBTRs (7.8%) were observed. Nine IBTRs (5.0% of the total cohort) and 10 CBTRs (5.6% of the total cohort) were invasive carcinomas. Eight of 9 IBTRs (88.9%) and 6 of 8 invasive CBTRs (75%) that had histologic sections available for review were of the lobular invasive type. Ninety-six percent of all IBTRs and 100% of invasive IBTRs occurred within the same site as the index LCIS. The numbers of invasive IBTRs were comparable within and after 5 years (5 invasive IBTRs vs. 4 IBTRs). Recurrences of invasive CBTR occurred later than recurrences of invasive IBTR, with 70% of invasive CBTRs recognized after 5 years compared with 44% of invasive IBTRs. It was found that Grade 2-3 LCIS was significantly predictive for invasive IBTR when combined with the number of recurrences of ductal carcinoma in situ (DCIS) alone or with LCIS. Only 2 patients in the cohort (1.1%) succumbed to breast carcinoma; 1 patient had a prior invasive IBTR, and the other patient had an invasive CBTR. The reasons for the lower frequency of invasive recurrences and the higher proportions of the lobular invasive phenotype than noted by others are discussed along with the impact of the findings on the nomenclature, precursor nature, and treatment of LCIS. CONCLUSIONS: LCIS is a more indolent form of in situ breast carcinoma than DCIS, with which it shares other features of its natural history, particularly very low mortality rates. There is no compelling reason to surgically treat LCIS other than conservatively. The values of other adjuvant modalities in the management of LCIS are discussed. The authors acknowledge that their findings are based on relatively few events and, even at 12 years, may be regarded as "preliminary". Nonetheless, their findings may reflect the true biologic nature of LCIS.