Tumor staging and grade decisively influence the treatment and prognosis of invasive BC. [12]. Therefore, tumor stage must be precisely determined in order to select the best course of treatment. Radiological LN evaluations are limited because CT scans and MRI cannot identify metastases in LNs of normal size or those minimally enlarged [7]. Pelvic lymph nodes that are larger than 8 mm and abdominal LNs that are larger than 10 mm in their longest axis are considered enlarged by CT or MRI. The sensitivity of these methods for detecting lymph node metastasis varies from 48 to 87%. The specificity is also low because the enlarged LN is not necessarily a marker for further neoplastic disease [13, 14]. Currently, there is no evidence for the routine use of PET for evaluating LN staging in bladder cancer [15]. Therefore, clinical sub-staging of BC is a common problem. It is estimated that around 20–25% of T1-T4 N0M0 patients who are submitted to RC and LND present lymph nodal metastasis [16, 17], and these rates have been shown to increase with the progression of tumor staging [18]. Pelvic LND is the main LN staging method, and it has been suggested that increased lymphadenectomy extension leads to increased chances of cure [19]. LN identification can be improved by submitting the same samples in separate vials [16], by identifying specific solutions [20], and analyzing 3 mm sections [21].
LN micrometastasis is a marker of poor prognosis in tumors such as breast, lung, esophagus, stomach, uterus, and melanoma. SERAJ et al. studied 27 BC patients within Ta-T3N0 clinical stages. The biopsies of the largest tangible removed LNs were evaluated through RT-PCR for the presence of uroplakin II (UPII) mRNA. A total of 17% of the LNs from pT2N0 patients and 67% from pT3N0 patients presented lymph nodal micrometastasis [8]. RETZ et al. found 29% positivity when investigating the use of mucin 7 (MUC-7) expression in the detection of micrometastasis in histologically normal LNs [9]. The expression of cytokeratin 19 (CK19) and uroplakin II (UPII) were used in the evaluation of micrometastasis in 760 LNs from 40 patients who underwent RC with LND. Histopathological review detected 29 positive LNs in six patients; however, CK19 and UPII positive expression indicated the presence of lymph nodal metastasis in 49 LNs and 98 LNs, respectively. Patients with micrometastasis detected by these biomarkers showed poorer survival rates when compared with patients without micrometastasis, regardless of the presence of histologically positive LNs [22]. Recently, MARIN-AGUILERIA et al. analyzed the role of the expression of 5 genes in identifying LN micrometastasis using RT-PCR. The combined expression of two genes (FXYD3 and KRT20) differentiated the positive LNs from the controls (healthy) with 100% sensitivity and specificity. These authors showed that the expression of two genes identified positive LNs in 20.5% of the pN0 patients evaluated histologically [23].
YANG et al. [11] were the first to evaluate the immunohistochemical role of the AE1AE3 antibody in detecting micrometastasis in LNs in 229 LNs (pN0) from 19 invasive BC patients submitted to RC. Three sections were prepared for IHC, and one was stained by HE from each tissue block. The antibodies used in the IHC evaluation were CAM 5.2 and AE1AE3. Only one LN was positive for CAM 5.2. However, this micrometastasis could be observed through a more thorough analysis in a deeper section stained by HE. The authors concluded that LN analysis with HE method is adequate and has a better cost-benefit ratio compared to IHC for identifying metastasis in the pelvic LNs of BC patients. Conversely, ABE et al. [24] recently analyzed the role of AE1AE3 in the diagnosis of micrometastasis in LNs from patients with upper urinary tract urothelial carcinoma who underwent nephroureterectomy associated with retroperitoneal LND. Seven hundred and fourteen LNs from 51 patients were reviewed with the HE method and analyzed for AE1AE3 reaction. Micrometastasis was identified in 7 patients (13.7%). No difference in survival was observed between patients with and without micrometastasis after 45 months of follow-up. In our study, only 2 patients considered as pN0 in the conventional histological evaluation showed lymph nodal micrometastasis. Survival analysis was not possible since both patients died from surgical complications during hospitalization. We observed that since 1996, the number of surgically dissected LNs has increased substantially, reaching an average of 20 LNs per patient in the last decade. Despite the dissection of many LNs and consequently, the increased number of LN analyses, none of them were positive for AE1AE3 in the IHC evaluation.
The finding of epithelial cells in the LNs, whether by IHC or the biomolecular method, does not necessarily indicate the occurrence of metastases, and thus, the morphological evaluation remains necessary. Benign epithelial inclusions represent ectopic foci of embryonic epithelium in the Müllerian ducts (paramesonephric ducts) that can be found in the lymph nodes, peritoneum pelvic, greater omentum, uterine ligaments, tubes, and ovaries. The exact frequency with which these inclusions are found in the pelvic and peri-aortic LNs is uncertain, ranging from 1 to 40% in the literature [25]. The importance of knowing the benign epithelial inclusions lies in the fact that they can be easily mistaken as metastatic foci.
Our data corroborate the results reported by YANG et al. [11], who concluded that a thorough histological analysis using the HE method by experienced BC pathologists is sufficient for the diagnosis of lymph nodal metastasis and, therefore, no indication for routine IHC evaluation in patients at pN0 stage is indicated. In addition, we believe that the LN analysis through a single section is sufficient for the diagnosis of lymph nodal metastasis. In conclusion, we do not recommend the indication of routine IHC evaluations of LNs of surgically treated pN0 BC patients.
