The number of lymph nodes is correlated with mesorectal morphometry

Can we apply the concept of sentinel lymph node in rectal cancer surgery?

INTRODUCTION

Colorectal cancer remains one of the most common causes of cancer-related mortality worldwide, and lymph node staging is crucial in the diagnostic and therapeutic process. Sentinel lymph nodes are the first involved in this process, but their validity in colorectal surgery has not yet been established. Following the emergence of new imaging instrumentation, some authors have attempted to propose different techniques for lymph node identification. However, a clear pattern of mesorectal lymph node distribution relative to the primary lesion site has yet to be defined.

MATERIAL AND METHODS

Our analysis retrospectively reviewed suspicious mesorectal pathological lymph nodes on pre-operative magnetic resonance imaging (MRI) of rectal cancer patients, in order to assess the distribution patterns of possible tumour-related rectal lymph nodes. Mesorectal space was subdivided into quadrants and levels, and morphological features and distances from the lymph node to the primary rectal tumour were recorded.

RESULTS

Two hundred and fifty-five mesorectal lymph nodes distributed among 60 patients were collected. Results show that in 92.1% of cases, nodes were distributed in the same mesorectal quadrant as the rectal primary tumour, and in 88.5% of cases, they were found at the same level as the rectal primary tumour.

CONCLUSIONS

Although a clear node distribution pattern was not established, these results may suggest at least a lymphatic drainage preference lane, worthy of further investigation.

Size and distribution of lymph nodes in rectal cancer resection specimens

BACKGROUND

The detection of lymph node involvement is fundamental to the staging of rectal cancer, and aids in prognostication and identification of patients who will benefit from adjuvant therapy. The anatomical variation in distribution and size of mesorectal lymph nodes has received scant attention.

OBJECTIVE

This study aimed to determine the size and distribution of lymph nodes in rectal cancer resection specimens.

DESIGN

This was a prospective, observational study of rectal cancer resection specimens analyzed by a single histopathologist.

SETTING

This study was conducted from January 2007 to July 2013 at the authors' institution.

PATIENTS

Two hundred forty-four consecutive patients underwent resection for rectal cancer.

MAIN OUTCOME MEASURES

The size and distribution of lymph nodes in the resection specimens and the anatomical position of mesorectal lymph nodes in relation to the peritoneal reflection, tumor, and anal verge were recorded.

RESULTS

A total of 10,473 lymph nodes were retrieved in 244 patients (75 women; median age, 68 years (interquartile range, 59-75 years)). One hundred seventy-three anterior resection and 71 abdominoperineal resection specimens were analyzed. Median lymph node yield was 41 lymph nodes (interquartile range, 31-52); 344 of 10,473 (3.2%) lymph nodes were positive. Lymph nodes were distributed in the mesorectum, sigmoid mesentery, and vascular pedicle in 40%, 32%, and 28% of the patients. Sixty-eight percent of mesorectal lymph nodes were above the peritoneal reflection. Mesorectal lymph node distribution in relation to the tumor was 53% above, 36% adjacent to, and only 11% below the tumor. Ninety-five of 334 (28%) positive nodes were ≤3 mm in diameter.

LIMITATIONS

Resection specimens analyzed by other pathologists (<5%) have not been included, and fat clearance techniques were not used to retrieve lymph nodes.

CONCLUSIONS

To ensure accurate nodal staging of rectal cancer, both resection and subsequent pathological evaluation should focus on the mesorectum in close proximity to the tumor and along the superior rectal artery. Small lymph nodes (<3 mm in size) should not be overlooked, and lymph node metastasis to the sigmoid mesentery is rare (see Video, Supplemental Digital Content 1, http://links.lww.com/DCR/A177).

Clinico-pathological factors influencing lymph node yield in colorectal cancer and impact on survival: analysis of New Zealand Cancer Registry data

BACKGROUND

Lymph node yield (LNY) and lymph node ratio (LNR) are recognized as independent prognostic factors in colorectal cancer (CRC).

OBJECTIVES

To examine the relationship between LNY and other clinico-pathological variables, and the prognostic value of LNY and LNR on patient survival in CRC.

METHODS

The clinico-pathological and survival data for patients diagnosed from January 2000 to July 2012 were retrieved from the New Zealand Cancer Registry. Multiple linear regression was used to identify clinico-pathological factors influencing LNY, and Cox regression was used to determine the association between LNY and LNR and patient survival.

RESULTS

14,646 patients were included in the study (mean age 70.3 years, 50.1% male). Mean LNY was 17.4. Younger age, right-sided disease, higher T stage, female sex and no neoadjuvant radiotherapy (rectal cancer) were all associated with higher LNY (P ≤ 0.001). Overall survival in Stage I-III disease increased with higher LNY (for LNY ≥ 12, HR = 0.67, 95% CI 0.64-0.72; P < 0.001). Survival in Stage III-IV disease was inversely related to LNR (HR = 0.56, 95% CI 0.51-0.62; P < 0.001).

CONCLUSION

LNY is influenced by patient age, site of disease and T stage. LNY (Stage I-II) and LNR (Stage III-IV) have independent prognostic value in CRC.

In vivo lymph node mapping and pattern of metastasis spread in locally advanced mid/low rectal cancer after neoadjuvant chemoradiotherapy

PURPOSE

The lymph node status is one of the strongest prognostic determinants in rectal cancers. After chemoradiotherapy (CRT), lymph nodes are difficult to detect. This study aims to evaluate the feasibility of lymph node mapping in the mesorectum after CRT to analyze the pattern of metastasis spread and to assess the reliability of blue dye injection in sentinel lymph node detection.

METHOD

Ten patients with cN+ mid/low RCs after CRT were prospectively enrolled. The protocol scheduled intraoperative blue dye injection, surgery, and specimen examination with fat clearance technique. The mesorectum was divided into three equal "levels" (upper, middle, and lower); each level was divided into three equal "sectors" (right anterolateral, posterior, and left anterolateral). Lymph nodes were defined "small" if ≤5 mm.

RESULTS

Two hundred seventy-six lymph nodes were retrieved in ten patients; 76.5 % were small lymph nodes. Six patients were pN+ (33 metastatic lymph nodes, 76 % small); small lymph node analysis upstaged one patient from N0 to N1 and four patients from N1 to N2. Metastasis distribution across sectors was continuous, without "skip sectors." The blue dye detected the sentinel lymph node in all patients; in half of the cases, it was out of the tumor sector. Blue dye identified 69.7 % of metastatic lymph nodes; its sensitivity decreased together with the metastatic deposit size (84 % macrometastases, 28.6 % micrometastases, 0 % occult tumor cells; p = 0.004).

CONCLUSION

The fat clearance technique should be the standard pathological examination in patients with RCs after CRT; N staging was improved by small lymph node identification. Lymph node metastases have a continuous spread through mesorectal sectors. Blue dye injection is effective in sentinel lymph node detection.

Lymph node distribution and pattern of metastases in the mesorectum following total mesorectal excision using the modified fat clearing technique

AIM

To define the distribution, size, location and metastasis of lymph nodes (LNs) within the mesorectum from rectal cancer specimens following total mesorectal excision (TME) surgery without neoadjuvant therapy.

METHODS

Specimens from 60 patients who underwent TME were treated with modified fat clearing solution to retrieve LNs. The mesorectum was divided into right lateral, anterior, posterior and left lateral sides, which were further subdivided into three levels (upper, middle and lower).

RESULTS

1436 LNs were harvested, including 985 small LNs (<5 mm in size). The number of LNs from the anterior, posterior and bilateral mesorectum was 125 (8.7%), 696 (48.5%) and 615 (42.8%), respectively. In the longitudinal axis, the difference in distribution at the three levels was not significant. 200 LN metastases (mLNs) were detected in 33 patients. 48% (96/200) of these were small LNs. More mLNs, especially small LNs, were shown in the more advanced T stage patients. The mLN metastasis rate was not influenced by tumour level.

CONCLUSION

Small LN detection increased the accuracy of N staging by 20% in this study. The incidence of metastasis was the same among the anterior, bilateral and posterior areas of the mesorectum. An increased incidence of mLN metastasis in small LNs was associated with more advanced T staging. mLN metastasis rates in both middle and low rectal cancer were higher in the distal mesorectum than that in the proximal mesorectum. LN number and density were not consistent with spread of the primary tumour. Distal mLNs were found in 35% of cases of both middle and distal rectal cancer, implying a need for TME in both.

[The lymph node of Mondor: myth or reality?]

AIM OF THE STUDY

Lymph node involvement is one of the most significant prognostic factors of patients with rectal cancer. Despite major advances in our understanding of the propagation of the rectal cancer, the lymphatic drainage of the rectum remains unclear. This study was designed to assess the number of lymph nodes located around the superior rectal artery and to assess the frequency of Mondor's lymph nodes.

PATIENTS AND METHODS

Twenty-five anatomic subjects were studied. All resections were performed using total mesorectal excision. Lymph nodes were sought in the tissue surrounding the superior rectal artery up to 2 cm under the ending of the superior rectal artery by manual dissection and were submitted for histological examination. The correlation between the number of lymph nodes, and the volume and weight of the tissue surrounding the superior rectal artery was evaluated by non-parametric Spearman test.

RESULTS

The mean number of lymph nodes per specimen was 2.7 +/- 1.4. The size of the lymph nodes varied between 1 and 7 mm. The lymph nodes were mostly smaller than 3 mm (56%). The number of lymph nodes in the superior rectal mesentery was independent of its volume and its weight. Seven subjects had a Mondor's lymph node. The mean size of Mondor's lymph node was 3.4 +/- 2.1 cm.

CONCLUSIONS

The number of NL located around the superior rectal artery is small, varying between 1 and 5. The Mondor's lymph node is an inconstant rectal NL. Its only characteristic is its location in the bifurcation or trifurcation of the superior rectal artery.

[What do we know about the lymphatic drainage of the rectum?]

Lymph node (LN) involvement is one of the most significant prognostic factors of patients with rectal cancer. However, the distribution of rectal LN is not well known. The rectal LN are mainly located around the rectal arteries. In the mesorectum, the LN are mainly located posteriorly. The number of LN by patient varies considerably. Many reasons can explain this variability. Acquired factors such as infection, inflammation or metastatic involvement facilitate the detection of LN. In contrast, preoperative radiotherapy reduces the number and size of lymph nodes. The procedure of resection affects the number of LN harvested. Extensive lymphadenectomies increase the number of LN harvested. The technique used by pathologist has equally a major influence. The fat clearing method allows detection of a greater number of LN than manual dissection particularly for small LN. Toxicity of these solutions and a time-consuming process explain that fat clearing method is rarely used in clinical practice. Detection of rectal lymph nodes is difficult and tedious but is necessary for an accurate staging of patients with rectal cancer.