The relevance of occult axillary micrometastasis in ductal carcinoma in situ

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Abstract
BACKGROUND Ductal carcinoma in situ (DCIS) represents 20% of newly diagnosed breast carcinoma cases. Historically, the incidence of axillary metastasis in DCIS has been small (1–2%) and its significance has been debated. It is widely known that serial sections of lymph nodes coupled with keratin immunohistochemistry (IHC) increases identification of micrometastasis. The advent of sentinel lymph node evaluation underscores the need to reevaluate the significance of occult micrometastases in DCIS. METHODS Patients with DCIS and negative axillary lymph nodes from 1974 to 1992 were selected from the Saint Barnabas Medical Center Tumor Registry. All diagnoses were confirmed, and paraffin blocks were retrieved after acceptance into the study. Seven serial sections were obtained from each block and evaluated with two cytokeratin IHC stains. Clinical follow‐up ranged from 10 to 28 years. RESULTS One hundred two patients were included in the study. Micrometastases were identified in 13 patients (13%), mostly on 1 level and composed of microscopic clusters in the subcapsular sinus. Seven of these lymph node–positive patients (58%) had high‐grade comedo DCIS, 4 (33%) had intermediate grades of various types of DCIS, and one had a low‐grade micropapillary DCIS. The overall disease recurrence rate was 12%, but micrometasis was not detected in any of the patients who developed disease recurrence. CONCLUSIONS Serial IHC evaluation of lymph nodes dramatically increased the identification of occult micrometastasis. However, IHC detected micrometastasis has no apparent clinical significance in DCIS, based on the current long‐term clinicopathologic study. Therefore, the authors questioned the significance of occult micrometastasis, identified by IHC, in DCIS of any type and extent. Further evaluation and follow‐up of lymph node micrometastases in patients with invasive tumors of various sizes are needed. The current findings would not support altering the stage of patients with DCIS and micrometastasis detected by IHC only. Cancer 2003. © 2003 American Cancer Society.