Sentinel Lymph Node Ultra-staging as a Supplement for Endometrial Cancer Intraoperative Frozen Section Deficiencies

Abstract

For endometrial cancer (EC), most surgeons rely on intraoperative frozen section (IFS) to determine the risk of nodal metastasis and necessity of lymphadenectomy. IFS remains a weak link in this practice due to its susceptibility to diagnostic errors. As a less invasive alternative, sentinel lymph node (SLN) mapping and ultra-staging have gradually gained acceptance for EC. We aimed to establish the SLN success rate, negative predictive value, and whether SLNs provide useful information for cases misdiagnosed on IFS. From 2013 to 2017, 100 patients (63 low-risk and 37 high-risk EC) underwent hysterectomy, bilateral salpingo-oophorectomy, and SLN. Among them, 56 had additional pelvic lymphadenectomy. A total of 337 SLNs were obtained in 86 cases: 55 bilaterally and 31 unilaterally. The remaining 14 cases failed because of patient obesity or leiomyoma. Pathology ultra-staging detected 2 positive SLNs from 2 patients (1 with isolated tumor cells, 1 with micrometastases). One of 773 nonsentinel pelvic nodes was positive on the contralateral hemi-pelvis in a patient who was mapped unilaterally, resulting in negative predictive value of 100%. During IFS, tumor grade and/or depth of myometrial invasion was misdiagnosed in 22 cases (22%). These errors would have resulted in under-staging in 10 high-risk patients or over-staging in 4 low-risk patients. SLNs were mapped in these misestimated patients, with one revealing metastases. SLN provides invaluable information on nodal status while detecting occult metastases in cases misdiagnosed on IFS. Our findings justify the incorporation of SLN in initial surgery for EC as an offset to IFS diagnostic errors, minimizing their negative impact on patient care.

The uterine pathological features associated with sentinel lymph node metastasis in endometrial carcinomas

“…Despite the limitations due to a relatively small sample size, the findings in this series as well as in other studies, support SLN resection for endometrial cancers [21,26,37,38]. This study identifies the following pathologic features as being highly associated with SLN involvement: 1) lower uterine segment involvement, 2) a tumor size of 5 CM or greater, 3) presence of histological lymphovascular invasion, 4) cervical stromal involvement, and 5) a depth of myometrial invasion of �50% while histological grades or microsatellite instability play no significant role.…”

“…Based on our study, the pathological features of low risk disease include 1) lack of LUSI, 2) a tumor size of less than 5 CM, 3) lack of histological LVI, 4) lack of CSI, and 5) a depth of invasion of less than 50%. There are studies that have evaluated some of these features individually [9,[24][25][26], but in the current study, we have made an attempt to stratify them collectively and emphasize their degree of importance. For example, Frimer et al and Kim et al had mainly associated the depth of myometrial invasion with SLN involvement [9,25].…”

“…For example, Frimer et al and Kim et al had mainly associated the depth of myometrial invasion with SLN involvement [9,25]. It should be emphasized that intraoperative pathologic assessment (frozen section) of hysterectomy specimens is essential to assess the extent of tumor involvement beyond the boundaries of corpus uteri [26].…”

“…Omitting lymphadenectomy holds the risk of inadequate staging, while SLN biopsy may be an acceptable alternative to the patients who would not benefit from complete lymphadenectomy [24]. Additionally, Blakely et al have suggested that incorporation of SLN biopsy during the initial surgery is useful to offset frozen section diagnostic errors [26].…”

Sentinel lymph node biopsy in endometrial cancer: state of the art

“…Non-SLN pelvic lymph nodes are cut perpendicularly to the long axis into 3 mm sections. One level is cut from each section and submitted for H&E staining ( 67 ).…”