[232] Should Sentinel Lymph Node (SLN) Biopsy Be Performed in Microinvasive Breast Carcinomas (MIC)?

Anupma Nayak, Sarah E Frost, Chandandeep S Nagi, Ira J Bleiweiss, Shabnam Jaffer. Mount Sinai School of Medicine, New York, NY

Background: The role of SLN biopsy in patients with MIC is questionable. To answer this question, we examined the incidence of lymph node (LN) metastasis in patients diagnosed with MIC at our institution.
Design: A retrospective review of pathology database between 1994 and 2012 identified patients with MIC who underwent surgery at our institution. MIC was defined as per current AJCC definition including only patients with invasive foci <1mm in size. Clinical and pathologic variables were recorded including the SLN/axillary lymph node (ALN) status. Five additional levels and 2 immunohistochemical stains (CAM5.2 and AE1/AE3) for cytokeratins (CK) were routinely done on all SLNs. LN metastasis were classified per current AJCC classification. Follow up data were recorded whenever available.
Results: Of 7000 patients operated for invasive breast carcinoma between 1994 and 2012, 99 (1.4%) were classified as MIC. Median age was 56yrs (range, 31 to 83yrs). Twenty eight patients underwent mastectomy and 71 had lumpectomy. Eighty one (82%) patients had SLN/ALN staging. Sixty four (65%) patients had SLN biopsy (avg. no. of SLN, 2). Seven (8.6%) of 81 cases showed isolated tumor (ITC)/epithelial cells in SLN. Three of these 7 cases showed reactive changes in LN (such as giant cells and hemosiderin laden macrophages), papillary lesion in breast with or without displaced epithelial cells within granulation tissue of biopsy site, or immunohistochemical (ER, PR and HER-2) discordance between the primary tumor in breast and LN, consistent with iatrogenically displaced epithelial cells rather than true metastasis. The remaining 4 cases included 2 cases, each with a single CK+ cell in the subcapsular sinus detected by IHC only; and 2 cases with ITCs singly and in small clusters (<20 cells per cross section) detected by H&E and IHC. The exact nature of CK+ cells in the former 2 cases could not be determined and may still represent iatrogenically displaced cells. In the end, there were only 2 cases (2.5%) with minimal tumor volume (ITC) in axilla. Three of these 4 cases had additional ALNs excised which were negative for tumor cells. Follow up data did not reveal axillary recurrence in our cases.
Conclusions: Our data suggests a very low incidence (2.5%) of SLN involvement only in the form of ITCs, in patients with MIC. None of our cases showed micro or macrometastasis. We recommend reassessment of routine practice of SLN biopsy in patients with MIC.
Category: Breast

Monday, March 4, 2013 8:15 AM

Proffered Papers: Section B, Monday Morning

 

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