Mediastinal Lymph Nodes Number and Sizes in Brazilian Adults
Aurelino Fernandes Schmidt Jr1*, Olavo Ribeiro. Rodrigues2, Roberto Storte Matheus2, Fabio Biscegli Jatene1
Abstract: The involvement of mediastinal lymph nodes in pathologic processes, with consequent volume increase is well known. However the normal size definition for the mediastinal lymph nodes remains unset. To determine the number and size of lymph nodes according to its position in the mediastinum, fifty human adult cadavers were dissected according to NARUKE/ATS-LCSG map (1997). A total of 1,742 lymph nodes were dissected, with a mean of 2.58 nodes for each station. A digital process was employed to measure area and major/minor axis of each specimen. The lymph nodes were present in 90% to 100% in stations #1, #2R, #4R, #5 and #7, and 28% to 82% in the other stations. The mean area, major and minor axis were larger in stations #7 (195.59mm2, 18.75mm¡Á 0.92mm) and #4R (115.32mm2, 13.72mm¡Á 8.30mm), with a mean of 49.41mm2, 9.40mm¡Á5.76mm in the other regions, respectively. The evaluation of the lymph nodes' sizes must be considered for each mediastinal region. Different size patterns could be presented in different populations. The lymph node size increased as function of coalescence due to previous granulomatous lesions, causing a decrease in the total number of lymph nodes.
Key words: lymph nodes; mediastinum; surgery; anatomy and histology; human
The importance of the mediastinal lymph nodes is regretted to its involvement in many neoplastic and infectious diseases, although the normal distribution and sizes of these lymph nodes are still unset. Nodal staging is dependent on knowledge of normal size, which is known to vary with patient environment .
Because the anatomical study of the mediastinum is possible to accomplish a normal pattern of the lymph nodes sizes and numbers in this specific population. The aim was to analyze the number and size of mediastinal region in the Brazilian population.
METHODS AND MATERIALS
Fifty-five cadavers with cause of death not directly related to diseases of the mediastinal nodes were dissected by the author. Five were excluded due to pleural carcinomatosis, pleural empyema, pachypleuritis and mediastinal fibrosis. Fifty were analyzed. 38 (76%) were male and 12 (24%) were female. The age varied from 36 to 90 years, mean 59.9¡À14.1 years. The cadavers were positioned in lateral decubitus and a posterio-lateral thoracotomy was performed. The right side was dissected first, completing the dissection by the following contralateral access. The mediastinal pleura was opened and all the mediastinal fat tissues were removed with the lymph nodes on it. The dissection was based on the anatomical repairs defined by the NARUKE/ATS-LCSG map (1997) . The mediastinal fat containing the lymph nodes were identified by the usual nomenclature and fixed in 10% formalin. After seven days of fixation, the lymph nodes were dissected from the mediastinal fat, counted and photographed by the milimetered scale. The images were obtained on a digital camera Sony Mavica FD97, using a resolution of 1,024¡Á 768 pixels, colors of 24 bits, with JPEG compression. The camera was fixed 4cm distant to the target, illuminated by two light sources to avoid shadows. The measures were obtained by using the UTHSCSA image tool program version 3, developed at the University of Texas Health Science Center at San Antonio, Texas. Each lymph node was delimited by its perimeter and the area, major and minor diameter determined after calibration.
The degree of shrinkage by formalin fixation was studied in thirty-six lymph nodes and did not showed significant difference. Histological analysis confirmed the absence of active pathologic process in all lymph nodes and permitted the discard of non-lymphatic tissues included in the dissection. It also allowed recounting the lymph nodes to determine the degree of coalescence. Non-active granulomas were present in tenlymph nodes in 8 cases. A value of coalescence was calculated for each case by the percentage of the number of lymph nodes counted after histological preparation (n-hist) in the number of lymph nodes (n-lymph) previously determined at dissection (value of coalescence = n-hist ¡Á 100% / n-lymph).
The statistical analysis was performed with the SPSS 9, the significant deference is at the levels of p<0.05.
The total 1,742 lymph nodes were dissected in 485 stations, with a mean of 2.6¡À1.9 for each region. 21.2¡À8.5 lymph nodes were identified at the right mediastinum, 13.6¡À6.3 at the left side, in a total of 34.8¡À12.2 by case. The lymph nodes were present in 90% to 100% in stations #1, #2R, #4R, #5 and #7, and 28% to 82% in the other regions. The histological study counted 158 coalescent lymph nodes, adding 9.1% to the total. The mean values were 72.9¡À84.0mm2 for area, 10.9¡À6.1mm for major axis, and 6.7¡À3.2mm for minor axis.
To accomplish 95% of confidence interval, the maximum standard value was calculated (¡À2¡ÁS). The mean long axis ranged from 10.9mm to 18.8mm in station #3a, #4R, #5, #7 and #8, and from 7.6mm to 9.4mm in the remaining regions. The mean minor axis was longer in station #7 (10.9mm) and ranged from 4.8mm to 8.30mm in the other regions. The mean area was larger in station #7 (195.59mm2) and #4R (115.32mm2), and ranged from 26.83mm2 to 68.25mm2 in the other stations (Fig. 1).
Fig. 1 Lymph node minor axis sizes according to the author
The coefficient of variation was lesser in the measures of area for station #4R and #7. The correlation among the number of lymph nodes and the value of coalescence was significant (p<0.05) (Fig. 2). The sizes of station #7 are significant difference from the others, which confirmed by The Bonferroni test, either is station #4R, and the sizes of station #3a and #5 are no difference from the others. The major axis was progressive smaller as the lymph node number increases (p<0.05) (Fig. 3). The presence of granulomas was associated to a greater presence of coalescence (p<0.001).
Fig. 2 Coalescence and lymph nodes number
Fig.3 Major axis and lymph node number
In this study, the major axis was longer in cases in which some nodes had non-active granulomatous disease. The incidence of these diseases can affect the values used for standards. Murray observed that the tuberculosis caused a residual increase of the mediastinal nodes . Fernandez compared tomography and mediastinoscopy in the staging of lung cancer in Brazilian population. He observed 23% of infiltration by lung cancer when the mediastinal lymph nodes were larger than 20 mm in major axis. The same size, in other populations showed infiltration over 80% .
There are controversies about an ideal cut-off value for normal minor axis but 1 cm had been generally accepted. Lymph node sizes that were greater than those observed by other authors were found in the population studied [4-6].
The measures of stations #4R and #7 were significantly greater than the others. The findings of greater nodes located in the contiguous carina were also described by other reports [4, 6].
The normal lymph nodes were classified in three groups with respect to the maximum normal size (Table 1). A map containing the maximum standards for each lymph node site was showed in Fig. 4.
Table 1. Maximum standards for lymph node sizes
StationArea (mm2)Major axis (mm)Minor axis (mm)#73503420#4R2703016Others1902412
Fig. 4 Maximum standards for each lymph node station
The number of dissected lymph nodes is various in different reports. The authors found 35 to 77.4 lymph nodes in both sides included hilar and mediastinal regions. When hilar regions were excluded, the bilateral mediastinal dissection findings varied from 9.4 to 30.1 lymph nodes [1, 7-9]. Our findings were 21.2¡À8.5 lymph nodes at the right side and 13.6¡À6.3 at the left side of the mediastinum.
The distribution, number and size of the lymph nodes are stable in the study based on the interval of ages, and do not suffer influence from the sex, race, weight or height. The coalescence was observed in 32.2% of the stations. The lymph node size increase in it's functioning of coalescence due to previous granulomatous lesions, causing a decrease in the total number of lymph nodes.
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(Edited by Xia Gao, Yanling Xiao, Yang Zhao and Yingqi Zhao)
* Corresponding to Aurelino Fernandes Schmidt Junior, MD, PhD; Address: Av. Frederico Straube, 512, Mogi das Cruzes -S?o Paulo - Brazil, Postcode: 08790-310; Tel: 55 11 4799 8317; E-mail: firstname.lastname@example.org
1 Thoracic and Cardiovascular Surgery Department, University of Sao Paulo, Brazil.
2 Thoracic Surgery Department, University of Mogi das Cruzes, Brazil