Lymph Nodes : Surgical Pathology Dissection

Lymph Nodes

High-quality sections for routine light micros-copy are necessary, but not always sufficient, for the interpretation of lymph node biopsies. Immu-nophenotypic and genetic studies are often re-quired for the diagnosis and classification of a hematopoietic neoplasm. Adequate fixation and timely and appropriate technical handling of lymph nodes are, therefore, even more important than with other specimens.

When lymph nodes are placed in an empty specimen container or in dry gauze, the edges of the specimen dry out, producing a prominent desiccation artifact at the edge of the node. Severe edge artifacts can be introduced into a lymph node even before the specimen reaches the surgi-cal pathology laboratory. Surgeons should there-fore be instructed to place resected lymph nodes immediately into a balanced physiologic solution such as Roswell Park Memorial Institute medium (RPMI) 640 or isotonic saline, and to transport lymph nodes immediately to the surgical pathol-ogy laboratory. Remember that lymph nodes can also dry out on the cutting table, so proceed quickly and efficiently after removing the speci-men from the transport media.

Once the specimen is received, document its size, weight, and shape, and then slice it into uniformly thin 2- to 3-mm sections. Examine the cut surfaces of the node, and ask the following questions: Is the nodal architecture preserved? If the architecture is ablated, is the node grossly nodular, or is the process diffuse? Are any focal lesions present? Is the capsule intact? What is the appearance of the perinodal tissues?

Next, prepare touch imprints by placing the surface of a glass slide against the cut surface of the lymph node. At least five air-dried slides should be prepared, especially in cases of sus-pected Burkitt’s lymphoma, lymphoblastic lym-phoma, and myelogenous leukemia. These can be used later for Giemsa stains, oil red O stains, acid phosphatase stains, chloracetate esterase stains, and immunofluorescence for nuclear terminal transferase. Two additional imprints immediately fixed in 95% alcohol should be prepared for possible hematoxylin and eosin (H&E) staining.

Next, tissue should be submitted for light mi-croscopy and, if sufficient tissue is available, for immunohistochemical and genetic studies. Sec-tions for light microscopy should include not only the substance of the node, but also the capsule and perinodal soft tissues. Submit at least one section for fixation in neutral buffered formalin and at least one section in B-5 or an equivalent fixative. The B-5 fixative contains mercuric chlo-ride as well as formaldehyde, and it provides crisp nuclear detail. If a section is submitted in a mercury-based fixative, remember to notify your tissue processing laboratory personnel because these sections require special processing.

When submitting fresh tissue for special stud-ies, collect the sample from solid ‘‘fleshy’’ areas of the tumor. Avoid areas that appear necrotic or sclerotic as these areas may not contain a sufficient quantity of viable tumor cells. The best techniques for submitting fresh tissue for im-munophenotyping will depend on your individ-ual laboratory, but in general a representative section of the node should be snap-frozen in opti-mal controlled temperature embedding medium for frozen tissue specimens (OCT) for immuno-histochemical studies, and a separate 0.5- to 0.7-cm cube should be submitted fresh for flow cytometry. Again, the rapid handling of tissue for these studies is crucial, because delays canresult in diffusion artifacts during immuno-staining. If tissue will be sent off-site for these analyses, it should not be frozen, but instead it should be kept cool on ice and rapidly trans-ported.

If adequate tissue is available, and it usually is, fresh tissue should also be sent for genetic studies such as gene rearrangements and kar-yotyping. Submitting this tissue is important because antigen receptor gene rearrangement analysis may be required in those rare cases for which morphology and immunohistochemistry alone cannot establish the diagnosis. Obtain in-structions on how to submit these specimens properly from your genetics laboratory.

Finally, if an infection is suspected or granu-lomas are encountered on a preliminary frozen section evaluation, fresh sterile tissue should be submitted for microbiologic studies. 

Important Issues to Address in Your Surgical Pathology Report on Lymph Nodes

• What procedure was performed, and what structures/organs are present?

• Anatomically, from where were the lymph nodes removed?

• What are the type and grade of the neoplasm?

• What are the number and size of the lymph nodes involved by tumor?

• What special studies were performed, and what were the results of these studies?

Extranodal Specimens

The lymphatic system is not limited to lymph nodes but encompasses diverse tissues and organs including the spleen, thymus, bone marrow, Waldeyer’s ring, vermiform appendix, and mucosa-associated lymphoid tissue of the intestines and lung. Lymphomas can arise anywhere in this rather extensive lymphatic system. Moreover, they can arise in extranodal sites that are not part of the lymphatic system (e.g., thyroid, stomach).

If the nature of a tumor is unknown at the time of specimen processing, a touch prep or frozen section of the tumor is a fast, simple way to determine if you are dealing with lymphoid proliferation. This is important information to have as you begin the dissection because extra-nodal lymphoid proliferations, like their nodal counterparts, need to be submitted for special studies as appropriate. Once tissue has been ob-tained for special studies, the specimens canthen be routinely processed in an organ-specific manner. There is no need to modify your ap-proach in any significant way. Similar to dealing with some epithelial neoplasm, remember to document the dimensions of the tumor, deter-mine the degree of involvement of adjacent struc-tures, assess the status of the surgical margins, and evaluate the regional lymph nodes. The un-involved tissues should also be sampled, and any additional pathologic processes (e.g., Helico-bacter pylori infections in stomach resections,thyroiditis in thyroid resections) should be in-cluded in the final pathology report.