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SEER Inquiry System - Report
Produced: 01/05/2026 12:19 AM
Question 20240066
Inquiry Details
References:
WHO Class Hem & Lymph Tumors. 4th and 5th editions
Question:
Histology--Heme & Lymphoid Neoplasms: How should histology be coded for a pathologic diagnosis of “Follicular lymphoma, diffuse pattern grade 3A of 3, equivalent to diffuse large B cell lymphoma (germinal center cell type)” when later referenced clinically as follicular lymphoma grade 3A? See Discussion.
Discussion:
The WHO Classification of Hematopoietic Tumors (Blue Book), 5th edition states: “Rare cases of classic follicular lymphoma with cytological features of follicular lymphoma (FL) grade 3A can present with a prominent diffuse pattern. In the previous edition, such cases were defined as diffuse large B-cell lymphoma (DLBCL). Currently, it is uncertain whether such cases should be classified as FL or diffuse large B-cell lymphoma; and in such cases, individual treatment choices should be made in multidisciplinary conference settings taking into consideration clinical, laboratory, and imaging parameters. The presence of diffuse areas composed entirely or predominantly of large cells, however, warrants a diagnosis of diffuse large B-cell lymphoma.”
Our concern is that the Hematopoietic (Heme) Manual and Database do not provide instruction for coding this scenario. We hesitate to interpret the terms “equivalent to” as ambiguous because one could argue it is unambiguous. Barring this argument, the M and H rules would indicate this is a diagnosis of diffuse large B-cell lymphoma. However, the physician does not seem to agree with the pathologist.
Answer:
Assign histology as DLBCL (9680/3) as supported by the WHO Classification of Hematolymphoid Tumors, 5th edition. It is consistent with how it would have been coded in the 4th edition. The Heme Manual and Database currently are based on the 4th edition. Physicians are using the 5th edition blue book, whereas the cancer registry field is not yet at this time.
Regarding the Heme Manual and Database, this type of scenario is not covered because it is part of the 5th edition WHO Blue Book. The database cannot be updated until the 5th edition is approved for implementation (2026).
