[Sentinel lymph node biopsy with micrometastases in breast cancer: histological data and surgical implications. About a series of 201 axillary dissections after peroperative sentinel node identification].

The benefit of systematic dissection of the non-sentinel lymph nodes (NSLN) in case of micrometastases (> or = 2 mm) in sentinel lymph nodes (SLN) is still being debated. The purpose of this work was to identify, from the histological characteristics of the micrometastases and the primitive tumors out of a series of 201 invasive breast carcinomas, of which 57.2% were pTl, which axillary dissection could be avoided. All cases had axillary dissection after peroperative SLN identification. The SLN were examined after fixation hy HE and immunohistochemical techniques (IHC), over their entire thickness from 2 to 3 mm-thick blocks of tissue and according to levels of histological sections with a spacing of 500 microm. The SLN were metastasized in 87/201 cases (43.3%) and in 29/8 7 cases (33.3%) it concerned micrometastases, 2/3 of which was only detected by IHC. The ability to discover micrometastases was proportional to the number of histological sections analyzed (58.6%, 82.7% and 100% of discovery with 1, 3 and 5 levels per block respectively). In 8/29 cases (27.6%) the NSLN were metastasized and in 6/8 cases it concerned macrometastases (> 2 mm). Taken separately, the characteristics of the tumors (size, histological type, grading, angioinvasion, multifocality), of the micrometastases (HE detection vs IHC detection, size, number) and of the site of injection of the radiotracer (peritumoral versus sub-areolar) did not allow us to isolate a group with micrometastases in the SLN but without metastases in the NSLN. However, the nine pT1 ductal carcinomas without angioinvasion were all NSLN negative. In conclusion, these results show that identification of micrometastases in SLN may influence the surgical decisions of re-excision, and that methodology of the pathological analysis is determinant.