Primary Extranodal Follicular Lymphoma

The journal Hematological Oncology just published an article called "Primary Extranodal Follicular Lymphoma: A Retrospective Survey of the International Extranodal Lymphoma Study Group (IELSG)." It actually doesn't affect most of us directly, but I think the bigger picture is probably important to us all.

The study described in the article looks at Primary Extranodal Follicular Lymphoma.

Extranodal FL means FL that exists outside the lymph nodes, and other organs related to the lymphatic system like the spleen and bone marrow. It's fairly common for FL to move out of the lymph nodes and into the spleen or bone marrow -- that's the very definition of stage 4 for FL, and about a quarter of FL patients are diagnosed with that stage. 

And if the lymphoma starts in the lymph nodes and then moves somewhere else, it's called secondary extranodal FL.

This article looks at primary extranodal FL -- it starts in some part of the body other than the lymph nodes.  

As I said, this doesn't apply to most of us, but I have communicated with a few readers over the last couple of years who have had their FL present in this way. Maybe some of you are still reading.

The research was conducted by the International Extranodal Lymphoma Study Group (IELSG), made up of Lymphoma experts who are specialists in these types of Lymphomas. Keep in mind that "Lymphoma" is a very broad term, and there are as many as 90 different types of Lymphoma, depending on who is doing the counting. About 30 of them are Extranodal types.

This research looked specifically at Primary Extranodal Follicular Lymphoma. This seems much less common than other types of Extranodal Lymphomas. I say "seems" because, as the authors note, extranodal FL "has not been extensively described." So they set out to find as much as they could by surveying specialists about cases that they had documented. They looked at "605 pathologically reviewed cases from 19 different countries" so they could compare the clinical features at diagnosis and their outcomes, and compare them to nodal FL.

What they found was that the two most common sites for Extranodal FL were the skin (334 of the 605 they looked at) and the gastrointestinal tract (72 of 605). More importantly, those two subsets were very different from nodal FL and had different Overall Survival patterns. After a median follow-up of 5.5 years, the cutaneous (skin) FL had an 89% 10 year OS, and the gastrointestinal FL had a median 10 year OS of 79%. For those gastrointestinal FL that presented in the duodenum (the first part of the small intestine), the OS was 95%. Other extranodal FL sites were similar to nodal FL. 

I think this is all good news for those of you with Primary Extranodal FL.

The bigger picture, though, is what interests me more. The researchers conclude by saying "These findings support the identification of specific primary FL localizations as distinct entities with particular clinical and biological characteristics." In other words, not all FLs are the same.

In some ways, that's really obvious. FL has a reputation for being heterogeneous -- it seems like we're all a little bit different. That was the conclusion of one of the ASCO presentations that I reviewed a couple of weeks ago. 

And yet, as obvious as it seems, we're still all kind of lumped in together as "Patients with Follicular Lymphoma." I think this goes back to not so many years ago, when diagnosis was done mostly by microscope. On the surface, all FL cells look very alike. As diagnostic tools, and our understanding of genetic features, becomes more sophisticated, it gets easier to see the differences. So some of us are probably still close enough to be a patient with FL, and to follow the same treatment recommendations as everyone else.

But that greater recognition that not every FL is the same will have significant implications in the future. We already know that, for example, grade 3B FL isn't really like other FLs. And POD24 FLs aren't really the same as others. But the more researchers can recognize specific features of different subtypes, the better off we will all be when it comes to diagnosis and treatment.

So that's my takeaway from all of this. It seems like very positive news for those of you for with Primary Extranodal FL. And for all of us, it's at least a small step toward making FL a little more manageable by identifying the things that make it heterogeneous. 

And those small steps are what move us forward.