Background
Positive sentinel lymph node (SLN) findings in DCIS range from 1–22% but have unknown biologic significance. We sought to identify predictors of positive SLNs and to assess their clinical significance in patients initially diagnosed with DCIS.
Methods
We identified 1234 patients with an initial diagnosis of DCIS who underwent SLN dissection (SLND) at our institution (1997–2011). Positive SLN findings were categorized as isolated tumor cells (ITCs) (≤0.2mm), micrometastases (>0.2–2mm), or macrometastases (>2mm). Predictors of positive SLNs were analyzed, and survival outcomes examined.
Results
Positive SLN findings were identified in 132 patients (10.7%): ITCs 66 (5.4%), micrometastases 36 (2.9%), and macrometastases 30 (2.4%). Upstaging to microinvasive (n=68 [5.5%]) or invasive (n=259 [21.0%]) cancer occurred in 327 patients (26.5%). Factors predicting positive SLNs included diagnosis by excisional biopsy (OR 1.90, P=.007), papillary histology (OR 1.77, P=.006), DCIS >2cm (OR 1.55, P=.030), >3 interventions before SLND (OR 2.04, P=.022 [4 interventions]; OR 3.87, P<.001 [≥5 interventions]), and occult invasion (OR 3.44, P=.001 [microinvasive]; OR 6.21, P<.001 [invasive]). Median follow-up was 61.7 months. Patients with pure DCIS with and without positive SLNs had equivalent survival (100.0% vs 99.7%, P=.679). Patients with occult invasion and positive SLNs had the worst survival (91.7%, P<.001).
Conclusions
Occult invasion and more than 3 total interventions were the strongest predictors of positive SLN findings in patients initially diagnosed with DCIS. This supports the theory of benign mechanical transport of breast epithelial cells. Other than patients at high risk for invasive disease, routine use of SLND in DCIS is not warranted.
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