The intraoperative evaluation of lesions suspicious for lymphoma or other hematologic diseases differs significantly from the more routine frozen section assessment of typical surgical pathology specimens. As outlined in the WHO classification of tumors of hematopoietic and lymphoid tissues (1), a complete assessment of hematopoietic material may require varying combinations of morphology, immunohistochemistry (IHC), flow cytometry, cytogenetic analysis, and molecular diagnostic evaluation. Therefore, rather than attempting to provide an immediate diagnosis, the rationale for intraoperative evaluation is three-fold; to identify the lesion as “hematopoietic,” to ensure the material is sufficient for diagnostic studies, and to appropriately triage the tissue so that morphology can be supplemented with relevant ancillary studies for the particular case. In this chapter, we discuss this approach to hematopoietic material in the gross room, outlining basic algorithms that can be used for proper specimen triage.

Generally, the request for biopsy of a lesion suspected of being lymphoma or another hematolymphoid disorder is initiated by a hematologist/oncologist and communicated to a surgeon or interventional radiologist. At the University of Chicago, a request for “lymphoma workup” alerts the surgeon and gross room staff that fresh tissue is required and that an on-call pathologist needs to be notified. Unlike routine biopsy specimens that are received in formalin, fixed material is not suitable for many ancillary studies such as flow cytometry, cytogenetics, and in some cases molecular diagnostic studies. Therefore, fresh tissue placed on a nonabsorbent gauze/paper (e.g., a Telfa pad) with a drop of saline or growth medium-RPMI to avoid drying is ideal. It is notable that a small biopsy placed on regular gauze can get lost in the fibers of the gauze, and that a small biopsy can also get lost or even become dissociated in a container full of saline. Often, there is confusion in the surgical suite regarding what “fresh,” “frozen,” or “fixed” material entails, and clear communication among hematology/oncology, pathology, and surgery is necessary to ensure that material is received in an appropriate fashion.

Sometimes, a biopsy specimen will be subject to frozen section only to be subsequently recognized as a hematolymphoid process. In such
cases it is wise to conserve all remaining tissue and request additional samples not to be frozen. Since tissue from patients with both known and/or suspected hematologic/lymphoid disease is diagnostically invaluable and usually scarce, it is wise not to fix or freeze material reflexively. In general, material from lymphoid organs such as enlarged lymph nodes, retroperitoneal masses, and mediastinum is best considered “hematopoietic” tissue for gross room triage. Extranodal tissue with a primary concern for a hematolymphoid process should also be handled the same way.

The pathologist should be familiar with details of the patient’s history, the site of the lesion, specifics of prior diagnoses (if any), and pertinent laboratory values especially related to peripheral blood. The objective of tissue evaluation in this setting is not for a final diagnosis. When fresh material is received, the immediate questions that need to be addressed include (1) whether the material is lesional tissue, (2) whether it is indeed hematolymphoid, (3) if there is enough tissue for diagnosis and appropriate subclassification, and (4) how the material should be divided for morphology and ancillary studies, particularly if material is insufficient for all modalities of analysis. This initial evaluation typically begins with a touch imprint preparation.

In contrast to the routine surgical pathology specimen, freezing of hematolymphoid tissue has limited utility and is generally discouraged. Not only does freezing involve potential wastage of precious tissue, the interpretation of frozen hematopoietic material is fraught with difficulty due to the inadequate representation of cellular detail. Histologic morphology is indeed crucial in proper interpretation of hematopoietic lesions, but freezing-related artifactual changes in cellular morphology make even the basic assessment of malignant versus benign unfeasible (2). The classic examples are differentiating follicular lymphoma from a reactive follicular hyperplasia, or distinguishing anaplastic lymphoma from metastatic carcinoma; neither can be reliably done on the frozen section alone. However, as noted above, the goal of the evaluation is not rendering a final diagnosis but deciding on appropriate division of tissue for ancillary studies. In this regard, touch imprint cytology is a simple and effective tool in initiating the appropriate diagnostic algorithm for a specimen suspicious of a hematolymphoid disease (3,4). A general approach of how a touch imprint is prepared is outlined in Table 3.1. Based on the patient’s history and touch imprint findings, the specimen is directed toward varying combinations of ancillary studies as appropriate: IHC, flow cytometry, cytogenetic analysis (including fluorescence in situ hybridization [FISH]), and/or further characterization by molecular diagnostics if needed. Touch preparations are very quick to perform and increasingly useful in the gross room especially if there is limited tissue since there is no wastage of precious material (5).

On the touch imprints, lymphoid or myeloid cells present as collections of discohesive cells, often with a variable inflammatory background. In contrast, nonhematopoietic (epithelial) cells are often cohesive, and three dimensional with touching or overlapping borders. The cells may display molding and form tissue structures such as glands or have fibrillary cytoplasm indicative of keratin or other cellular material which essentially rules out a hematopoietic process. Pitfalls include poorly differentiated carcinomas, sarcomas, small round blue cell tumors, and neuroendocrine malignancies, all of which may mimic lymphoid neoplasms. Of note, melanomas may display extremely variable morphology and should always be considered (and may require inked margins). In some situations, it may be necessary to revert to a frozen section when the initial results from the touch imprint suggest that the process is not hematopoietic as initially thought. In such situations, the touch preparation has not wasted material and has hopefully not provided much of a time delay for the surgical team.

The recognition of cell patterns on touch imprints will help dictate the appropriate further workup of the specimen. These patterns include predominantly large cells, blasts, monotonous small lymphocytes, and mixed populations of cells. The following sections describe these patterns, their differential diagnoses, and appropriate ancillary studies which we feel are needed for their evaluation (summarized in Table 3.2). It is important to point out that if the tissue biopsy is of adequate size, material for all studies can be easily submitted, but with smaller and smaller biopsies, and the need to be more judicious in ordering unnecessary testing, a careful initial evaluation can help ration both biopsy material and resources.