Ductal Carcinoma In Situ with Microinvasion

Abstract

: The natural history of patients with ductal carcinoma in situ (DCIS) and microinvasion is poorly defined and the clinical management of these patients, with particular reference to management of the axilla, has been controversial. Studies addressing this lesion have used highly varied and sometimes arbitrary criteria for the evaluation of microinvasion. At the Armed Forces Institute of Pathology, we have defined microinvasion as a single focus of invasive carcinoma ≤ 2 mm or up to three foci of invasion, each ≤ 1 mm in greatest dimension. Such minuscule invasive carcinomas are apparently rare, accounting for considerably less than 1% of cases of breast carcinoma reviewed in consultation at our institution. To determine the frequency of axillary lymph node metastases associated with this lesion, we retrospectively reviewed 38 cases of DCIS with microinvasion (n= 29) or probable microinvasion (n= 9), all treated with mastectomy and axillary node dissection between 1980 and 1996. The foci of microinvasion ranged from 0.25 to 1.75 mm (mean 0.6 mm) in greatest dimension and were present adjacent to DCIS in 95.3% of cases. The extent of DCIS did not correlate with the number of foci of microinvasion. Axillary node dissections yielded a mean of 19.3 lymph nodes (range 7-38) and all lymph nodes were negative for metastatic tumor. None of 33 patients, followed for a mean of 7.5 years (range 1.0-14.4 years), developed local recurrence or metastasis. While the cases of microinvasive carcinoma evaluated in this study were not associated with axillary node metastases and appear to have an excellent prognosis, further study is indicated to determine the appropriate management and long-term prognosis of patients with this lesion.