Best term for a Burkitt lymphoma with extensive BM involvement?

[Prashant Sharma]

Dear all,

we recently had a 6-year-old boy whose marrow was replaced by >95% abnormal lymphoid cells that fit Burkitt lymphoma morphologically and flow cytometrically. The cells were absent from peripheral blood. FISH revealed the t(8;14) in a majority of the marrow cells. An obvious primary site was not evident, although he had some CNS symptoms and a renal cyst.

My queries are, what would be the most accurate label for this child? Marrow involvement by Burkitt lymphoma? Burkitt leukemia/Burkitt cell leukemia? Or something else? Does the cut-off of >/=25% abnormal cells in marrow to decide between the terms "leukemia" versus "lymphoma involvement" only apply to "lymphoblastic" leukemias/lymphomas or is it a general thumb-rule for all NHLs?

In the 2016 WHO [2], a "Burkitt leukemia variant" is not there in the main list, but it finds mention in the chapter as a separate heading. The SEER database [1] says its been listed since 2001 in the ICD, but should not be used if there is only marrow involvement without blood involvement. So can this case, without any abnormal cells in the blood film, be labelled Burkitt leukemia?

And on a related note, are the subheadings in the WHO book, disease entities? I mean, there is a subheading for lymphoepithelioid lymphoma/Lennert's lymphoma under PTCL (NOS), but is Lennert's lymphoma a WHO-recognized diagnostic entity?

Thanks in advance for your responses. I know it's mostly semantics as long as pathologists and clinicians know what is being referred to. But its confusing if the same thing has many names...

Best regards,

Prashant Sharma

[1] http://www.bloodjournal.org/content/127/20/2375?sso-checked=true#T1

[2] https://seer.cancer.gov/seertools/hemelymph/51f6cf59e3e27c3994bd544a/