Isolated tumor cells in sentinel lymph nodes of invasive breast cancer: cell displacement or metastasis?

Risk factors of sentinel and non-sentinel lymph node metastases in patients with ductal carcinoma in situ of the breast: A nationwide study

OBJECTIVES

Unexplained axillary metastases have been detected in some patients with ductal carcinoma in situ (DCIS), possibly because of occult invasion or iatrogenic tumor cell displacement. The significance of these metastases is unknown and brings into questions the need for upstaging and axillary surgery. What are the risk factors for sentinel lymph node (SN) and non-SN metastases, including the risk of iatrogenic displacement of tumor cells in relation to an excisional biopsy, in patients diagnosed with DCIS?

METHODS

Nationwide data on 1787 women diagnosed with DCIS between 2001 and 2015 were retrieved from the Danish Breast Cancer Group database. The association of clinicopathological variables with a positive SN (isolated tumor cells (ITCs), micro- or macrometastases) was evaluated using univariate and multivariate analyses.

RESULTS

Of the 1787 patients, 71 (4.0%) had a positive SN: 15 (0.8%) had macrometastases, 42 (2.4%) had micrometastases, and 14 (0.8%) had ITCs. Five patients with a positive SN also had a positive non-SN. In adjusted analysis, a positive SN was associated with younger age (P = 0.036), increased size (P = 0.002), palpability (P = 0.0004) and surgical excisional biopsy (P < 0.001).

CONCLUSIONS

The overall risk of a positive SN in patients with DCIS on final pathology is low and less than 9% of these patients had positive non-SNs. This argues against using axillary lymph node dissection in this group. The odds of positive SN after surgical excisional biopsies showed more than a four-fold increase, indicating iatrogenic tumor cell displacement. It is questioned whether these patients should be upstaged and classified as having invasive carcinoma.

Sentinel Lymph Nodes in Classic Invasive Lobular Carcinoma of the Breast: Cytokeratin Immunostain Ensures Detection, and Precise Determination of Extent, of Involvement

The assessment of sentinel lymph nodes (SLN) on hematoxylin and eosin (H&E)-stained sections in cases of classic type of invasive lobular carcinoma (cILC) is considered unreliable, particularly in cases with minimal involvement, that is by either isolated tumor cells (pN0i+) or micrometastases (pN1mi). Although the impact of minimal SLN involvement has been shown to be insignificant in most clinical trials (even though cILC was either under-represented or not separated in the respective cohorts), the results of MIRROR trial did emphasize the need for additional therapy in cases with minimally involved SLN to ensure improved disease-free survival. We sought to study the role of cytokeratin immunohistochemistry (CK-IHC) in evaluating SLN in cILC. A total of 582 cILC cases with SLN diagnosed over a 12-year period (2005 to 2016) were reviewed. In all, 394/582 (68%) cases had H&E(-)/CK(-) SLN. In total, 188/582 (32%) cases showed some degree of SLN involvement of which 143/582 (25%) cases had readily identifiable SLN involvement on H&E slides. Overall, 45/582 (7.7%) cases had H&E(-)/CK(+) SLN. The following data relate to the latter subset of 45 cases. Mean age of patients: 61 y (range: 32 to 86 y); right: 24 (53%), left: 21 (47%); multifocal and/or multicentric: 22 (49%); mean size: 2.0 cm (range: 0.25 to 4.4 cm); mean number of SLN: 2.5; mean number of involved SLN: 1.2; and cases with prior needle core or excisional biopsy: 45 (100%). CK(+) cells were identified in isolation or in loose clusters, either in subcapsular sinuses or nodal cortex or both. Overall, 30/45 (67%) showed ≤200 CK(+) cells (ie, pN0i+), and 15/45 (33%) showed >200 CK(+) cells (ie, pN1mi). In total, 15/45 (33%) cases underwent axillary lymph node dissection, of which 4/45 (9%) cases were positive. cILC recurred in 3/45 (7%) cases. On statistical analyses, the number of CK(+) cells (≤/>200) did not correlate with either axillary lymph node-positivity or with recurrence. Number of CK(+) cells (≤/>200) readily distinguished pN0i+ from pN1mi based on AJCC's numerical criteria. CK(+) cells could be quantified in linear terms (ie, AJCC's size criteria of pN0i+ and pN1mi was applicable) in only 2 cases. On the basis of these findings, the use of CK-IHC staining should be considered for SLN in cases of cILC to ensure detection, and precise determination of extent, of involvement; however, the prognostic significance of this procedure would have to await results of additional studies with long-term follow-up.