Processing of the Lymph Node Biopsy Specimen

Instructions for the Surgeon

Knowledge of the patient's clinical history and the suspected diagnosis or differential diagnosis facilitates the search for a lymph node sample that best represents the underlying pathologic process. Despite the obvious appeal of convenient access, minimal discomfort, and procedural simplicity of excising a superficial lymph node, these lymph nodes are not always of diagnostic value. The surgeon should be encouraged to examine the patient thoroughly and sample the largest and most abnormal-appearing lymph node whenever possible ( Fig. 1-1 ). This approach avoids the erroneous sampling of enlarged or inflamed nodes adjacent to a previous biopsy site and enables more representative sampling. Imaging studies may help guide the surgeon to the most abnormal lymph node.

Excisional biopsy of an entire lymph node is preferred to an incisional or needle core biopsy because fragments of lymph nodes preclude a proper assessment of architecture, an important feature in establishing a morphologic differential diagnosis. When an infectious cause is suspected, the surgeon should be advised to submit a portion from one pole of the lymph node for appropriate microbiologic studies directly from the sterile environment of the operating room. In all other circumstances, the intact specimen should be submitted fresh to the pathologist in a specimen container and immersed in saline or culture medium to ensure that the specimen does not dry out during transit. Wrapping the specimen or laying it on gauze, sponges, or towels should be avoided because this leads to desiccation of the lymph node cortex, especially when the specimen is exposed to air. Request for a “lymph node workup” should be clearly indicated on the requisition slip or specimen tag, or both. Ideally, the pathologist should be notified at the time of the biopsy to avoid a delay in the handling of the specimen. When a delay in delivery to the pathologist is anticipated, the specimen should be refrigerated to minimize autolysis. Storage at 4° C for up to 24 hours can yield satisfactory but not optimal morphologic, immunologic, and genetic preservation. When long delays are expected before the pathologist receives the specimen, the surgeon may be instructed to bisect the lymph node and make air-dried imprints, after which the specimen can be sliced thinly and placed in buffered formalin. Portions should also be set aside for special studies.

Gross Processing of the Lymph Node Biopsy by the Pathologist

Gross Examination

The gross appearance of lymph nodes, including their color, consistency, and changes in contour, may provide useful information about the diagnosis and should be recorded during the gross inspection of the fresh specimen ( Fig. 1-2 ). Preservation of the hilus and the presence or absence of nodularity and fibrosis can offer important diagnostic clues. Preservation of the hilus is rare in lymphomas, and its presence suggests a reactive process (see Fig. 1-2, A and B ). Necrosis within the node raises the possibility of an infectious process and may prompt microbiologic studies. Adherence of the node to the surrounding fat may denote extracapsular extension of disease and should be noted in the gross description. Most lymphomas completely efface the nodal architecture, and a nodular appearance or fibrosis can be seen on gross examination (see Fig. 1-2, C to E ).

Although the gross findings can be helpful in narrowing the differential diagnosis, an accurate pathologic diagnosis is virtually never possible on the basis of the gross findings alone. Thus these findings must be interpreted in conjunction with microscopic features and immunophenotypic and genetic studies to establish a definitive diagnosis.