[168] Cytokeratin Positive Cells in Sentinel Lymph Nodes of pT1a Breast Cancers

Shabnam Jaffer, Chandandeep Nagi, Anupma Nayak, Robert Guarino, Ira J Bleiweiss. The Mount Sinai Medical Center, New York, NY

Background: It is known that in the setting of intraductal carcinoma (DCIS), particularly involved by intraductal papilloma, one must be cautious in interpreting cytokeratin positive (CK+) cells in the sentinel lymph node (SLN) since they may represent displaced epithelial cells rather than true metastases. Given the low rates of metastases in pT1a invasive carcinomas, we evaluated the effect of this phenomenon on staging.
Design: Using the computerized pathology database, we identified and reviewed the morphology and serially performed immunohistochemistry (ihc) in 35 pT1a breast carcinomas with SLN containing single and clustered CK+ cells.
Results: The CK+ cells were present as single cells and or clusters present in the subcapsular sinuses. We were able to classify the SLN findings as positive = 11 cases, negative = 11 and undetermined significance = 13. In the negative cases, in comparison to the primary, all the CK+ cells were uniform and lacked atypia, appeared papillary (2), and was accompanied by reactive changes such as giant cells (3). In the corresponding breast tissue, there was either displacement (10) and or an intraductal papilloma (11). All the primaries except 1 were estrogen receptor (ER) positive, in contrast to the CK+ cells which were ER negative. The ER negative tumor was Her2 positive but the CK+ cells were Her2 negative. In 1 invasive lobular case, we also took advantage of the E-cadherin stain which was negative in the primary but positive in the CK+ cohesive cells. In the positive cases, the CK+ cells showed similar atypical features with the primary. Only 1 case showed displacement, and 3 showed lymphatic invasion. Ihc was utilized in 2 cases showing similar ER positivity in both the primary and the CK+ cells. In the undetermined cases, the problem lay in the small number of single cells for comparison with the primary and further ihc study. In 1 case the primary showed heterogenous ER positivity which made interpretation of the ER negative cells in the SLN difficult. In another case the primary was ER positive but the CK+ cells although negative, appeared morphologically highly atypical.
Conclusions: Given the low rates of metastases in pT1a breast carcinomas, the identification of CK+ single and clustered cells in SLN should be resolved by morphology and or ihc whenever possible to prevent upstaging. Factors predictive of SLN postivity included multifocality and lymphatic invasion, and for negativity, the presence of displacement and or intraductal papilloma, while tumor size was not relevant.
Category: Breast

Wednesday, March 21, 2012 9:30 AM

Poster Session V # 22, Wednesday Morning


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