Intraoperative Imprint Cytologic Evaluation of Sentinel Lymph Nodes for Lobular Carcinoma of the Breast

The single most important predictor of outcome for women with breast carcinoma is the status of the ipsilateral lymph nodes.1–5 Traditionally, axillary lymph node status has been evaluated by routine axillary lymph node dissection (ALND) accompanying a lumpectomy or mastectomy. ALND is used to obtain precise staging data, provide local control for patients with metastatic breast carcinoma, and for the selection of adjuvant therapy.5–11 Unfortunately, the only patients that may truly derive therapeutic benefit from ALND are those patients with positive nodes, which corresponds to approximately 40% of those undergoing ALND.12–16 ALND is associated with considerable postoperative chronic morbidity, including lymphedema, neurologic injury, joint stiffness and, rarely, angiosarcoma.17–20 SLN biopsy is a highly accurate predictor of the overall axillary nodal status and has both a high sensitivity and specificity, especially when primary tumors are small.1,13,21–24 SLN mapping is attractive because it may identify a population of breast cancer patients that may benefit from ALND. More importantly, it may identify those patients in whom ALND and its associated morbidity may be avoided.1,13,21–24 The ability to stage patients intraoperatively via SLN biopsy is clearly desirable. This allows a single operative procedure to include ALND if the SLN contains metastatic carcinoma. Currently, intraoperative evaluation is performed using imprint cytology,25–32 frozen sectioning,33–42 or a combination of these techniques.44–46 The accuracy of frozen sectioning versus imprint cytologic evaluation are equivalent.47 The use of intraoperative imprint cytology (IIC) to evaluate the SLN for metastatic lobular carcinoma has not been reported in a large series. In a small series, the sensitivity of detecting lobular carcinoma in the SLN by a combined frozen section and imprint cytologic approach was discouraging.44 Because lobular carcinoma has low-grade cytologic features and tends to infiltrate lymph nodes in a single cell pattern, the distinction between lobular carcinoma and lymphoid cells can be extremely challenging. Because of this difficulty, the use of cytokeratin immunohistochemistry has become more or less standard for permanent section evaluation of metastatic lobular carcinoma. Although some groups have added cytokeratin immunohistochemistry to their intraoperative analysis, it increases turnaround time and cost.43 Therefore, in the present study, we analyze the utility of imprint cytology (without intraoperative immunohistochemistry) in the evaluation of SLN for lobular carcinoma in 61 consecutive lymph node mapping procedures performed at both an academic medical center and a community hospital.