Lymph nodes

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Author: Mikael Häggström [note 1]


On this resource, the following formatting is used for comprehensiveness:

  • Minimal depth
  • (Moderate depth)
  • ((Comprehensive))

Gross processing

If suspected lymphoma, before putting tissue in formalin, ensure that tissue is preserved in appropriate media for any special tests (usually flow cytometry). Further information: Lymphoma

In samples with tumors, slice through all included fat while palpating and looking for lymph nodes, and submit all that are found.

For lymph nodes taken for potential breast cancer metastasis, find out and report the procurement time and the time when put in formalin.[note 2]

Gross procedure

  • Measure the dimensions. For a lymph node with minimal surrounding fatty tissue, measure the greatest dimension (or 3 dimensions). For specimens with substantial amount of fatty tissue, measure the specimen in 3 dimensions, and measure the greatest dimension seen for individual lymph nodes therein after serial sectioning.
  • Find as many lymph nodes as you can in a specimen. Good locations to start include the presumed lymphatic drainage directions from a tumor, as well as when following the lymphatic directions from the vascular margins of a specimen. Serially section fatty tissue into slices that are thin enough to be palpated for small ovoid resistances. If you still have trouble finding enough lymph nodes, put fatty tissue in a vinegar and acetic acid solution made for the purpose of turning lymph nodes pale/white as well as making them more firm for palpation. Colon tumors are sometimes tattooed during endoscopy, and in such cases the tatoo ink often stains lymph nodes as well.
  • Section lymph nodes if needed. Lymph nodes less than 5 mm may be submitted whole, while larger lymph nodes may be sectioned at 2-3 mm intervals.[1]
  • Generally do not submit multiple sectioned lymph nodes in the same cassette, to allow exact counting of the number of involved lymph nodes on microscopy. If you will nevertheless submit multiple bisected lymph nodes in the same cassette, ink each lymph node differently.
Making a "touch prep": Press a glass slide against the cut surface of the lymph node, apply cytologic fixative solution immediately and stain with H&E.
  • If suspected lymphoma, such as an enlarged lymph node without any adjacent tumor or another almost certain cause, make a touch prep. Also, take a small fresh sample for flow cytometry:
  • For flow cytometry, aim for a tissue size of approximately 5 mm3. Put it in specific flow cytometry preservative medium (such as RPMI), and ensure it gets to the flow cytometry lab. If it is after normal hours and there is no one to ask to find such medium, you can put the specimen in normal sterile saline (enough to cover the tissue) in a fridge (2-8°C) until the next morning.[2] If you receive multiple lymph nodes for flow cytometry, still only sample one (unless the referral asks for separate flow cytometry studies, or there is a given history of one lymph node having high uptake and another having low uptake on PET scanning).

Definition of an enlarged lymph node

Long and short axis.png
  • By size, where lymphadenopathy in adults is often defined as a short axis of one or more lymph nodes is greater than 10mm.[3][4] However, there is regional variation as detailed in this table:
Upper limit of lymph node sizes in adults
Generally 10 mm[3][4]
Inguinal 10[5] – 20 mm[6]
Pelvis 10 mm for ovoid lymph nodes, 8 mm for rounded[5]
Generally (non-retropharyngeal) 10 mm[5][7]
Jugulodigastric lymph nodes 11mm[5] or 15 mm[7]
Retropharyngeal 8 mm[7]
  • Lateral retropharyngeal: 5 mm[5]
Mediastinum, generally 10 mm[5]
Superior mediastinum and high paratracheal 7mm[8]
Low paratracheal and subcarinal 11 mm[8]
Upper abdominal
Retrocrural space 6 mm[9]
Paracardiac 8 mm[9]
Gastrohepatic ligament 8 mm[9]
Upper paraaortic region 9 mm[9]
Portacaval space 10 mm[9]
Porta hepatis 7 mm[9]
Lower paraaortic region 11 mm[9]

Lymphadenopathy of the axillary lymph nodes can be defined as solid nodes measuring more than 15 mm without fatty hilum.[10] Axillary lymph nodes may be normal up to 30 mm if consisting largely of fat.[10]

In children, a short axis of 8 mm can be used.[11] However, inguinal lymph nodes of up to 15 mm and cervical lymph nodes of up to 20 mm are generally normal in children up to age 8–12.[12]

Lymphadenopathy of more than 1.5 cm - 2 cm increases the risk of cancer or granulomatous disease as the cause rather than only inflammation or infection.[13]


The processing of lymph nodes is preferably rushed when the H&E stain will determine whether immunohistochemistry will be performed, especially when a lymph node is submitted together with a separate specimen that may be solved without immunostains. This rushing allows you to have the immunostained slides by a similar time as the rest of the case.[14] Examples of cases that are preferably rushed for such reasons include those that may be stained by CK AE1/AE3 in order to visualize otherwise occult lymph node involvement if you don't see any involvement on the H&E stain, mainly in cases when one or more sentinel lymph nodes are submitted together with any of the following:

Rushing is not necessary for non-sentinel lymph nodes.

Gross report

Individual lymph node, example
((A. Labeled - ___. The specimen is received in formalin and consists of)) __ fragment(s) of soft pink-tan tissue, measuring __ cm in greatest dimension (or __ x __ x __(. (Representative sections are submitted for microscopic examination in __ cassettes.)
Multiple lymph nodes
((A. Labeled - ___. The specimen is received fresh and consists of)) 2 irregular fragments of yellow-tan fatty and fibrous soft tissue measuring __ and ___ cm in greatest dimension. Within the adipose tissue are multiple tan-brown lymph nodes measuring up to __ cm in greatest dimension. The cut surfaces display no gross lesions. The lymph nodes are entirely submitted for microscopic examination (in 10 cassettes).
  • A1–A3– one lymph node, serially section
  • A4-A5– one lymph node, serially sectioned
  • A6– one lymph node, bisected
  • A7– one lymph node, bisected
  • A8– two lymph nodes, each bisected, differentially inked
  • A9– one lymph node, bisected
  • A10– multiple lymph nodes.
Additional information
  • If potential breast cancer metastasis: The specimen was procured at __ AM/PM on (date), 2020. The specimen was placed in formalin at __ AM/PM on (date), 2020.
  • If lymphoma workup: A touch prep is made, and a minor part of the specimen is submitted for flow cytometry. The remainder of the specimen is submitted for microscopic examination in one cassette.

Microscopic examination

Defining a lymph node

For counting lymph nodes, each should have a discernible capsule around lymphoid cells. Also count larger free-standing lymphoid aggregates. However, the definition of what constitutes a lymph node is largely subjective.[15] Also strive to keep a consistency with the gross description. In addition, any cancer involvement is in itself a relative indication of being a lymph node.

General screening

Look for:

  • Whatever pathology is indicated by the referral, or findings in other submitted specimens.
  • Enlargement, as preferably measured during grossing, but can possibly be made on the microscopy slide. If present, see separate section below.

Microscopy of enlarged lymph nodes

Look at any other slides for the same case first, in order to find any pathology that may be reflected in in the lymph nodes as well, mainly cancer metastasis or reactive lymph nodes from inflammation.

Look primarily at the overall architecture, with main findings being:

  • Paracortical hyperplasia: Paracortical hyperplasia of a reactive lymph node shows expansion of paracortical areas by a mixed infiltrate, often having a mottled appearance, and it usually has a concomitant reactive follicular hyperplasia.[17] A T-cell lymphoma should be suspected if there is obliteration or marked diminution of the B-cell cortical region, or highly irregular or hyperchromatic nuclei.[17]
  • Unspecific hyperplasia: An unspecific pattern of lymph node enlargement, without atypical cells, in the lymphatic drainage direction from an inflamed area, may simply be diagnosed as "benign reactive lymph node".

Workup of cancerous lymph nodes

If cancer is detected in a lymph node:

  • Attempt to specify a specific cancer diagnosis'. If the patient has a known carcinoma or sarcoma etc, it is generally enough to confirm that it is consistent with a metastasis thereof.
  • Measure the size of involvement.
  • Look for extranodal extension.


A non-involved lymph node in a patient with cancer can be reported for example as:

Sentinel lymph node #1, left axilla, (excision):
One benign lymph node((, negative for malignancy (0/1))).

Cancerous lymph nodes with patients with known consistent cancer primary can be reported as metastatic,, such as:

Sentinel lymph node #2, left axilla, (excision):
Macrometastatic carcinoma involving one of one (1/1) lymph node.
Metastatic carcinoma measures 0.4 cm in greatest dimension.
(Negative for extranodal extension).


  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Patholines:Authorship for details.
  2. The duration that a specimen has been without formalin affects mainly the reliability of estreogen and progesteron receptor testing:
    - Pekmezci, Melike; Szpaderska, Anna; Osipo, Clodia; Erşahin, Çağatay (2012). "The Effect of Cold Ischemia Time and/or Formalin Fixation on Estrogen Receptor, Progesterone Receptor, and Human Epidermal Growth Factor Receptor-2 Results in Breast Carcinoma ". Pathology Research International 2012: 1–7. doi:10.1155/2012/947041. ISSN 2090-8091. 

Main page


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