TGCT vs PVNS

When I was diagnosed nearly 5 years ago my doctor called my bulging knee a case of "PVNS", Pigmented Villonodular Synovitis.  That is what I started researching.  What is this strange substance in my knee?  As I've seen several doctors over the years, they have indicated that different joints might carry a different name for the same substance if it's residing in a finger or other joint with synovial linings.  But for 5 years I've been calling it PVNS with a futile attempt to educate others on what PVNS is and how I suffer.  It's not so easy to explain and people always ask me, "what's that thing with your knee called again?"  Even with the easier remembered acronym it's not easy to remember.   However, in the last year a medical group in Europe have been reaching out to sufferers of PVNS and calling it TGCT, Tenosynovial Giant Cell Tumor.  I asked them why the name change?  They told me that it's what the World Health Organization recognizes as the true name of the disorder.  I have argued with these northern Europeans at length that it is confusing to add names to something that is still so rare.  They want me to participate in their studies but I have a really hard time saying I have TGCT.  There should only be one name!  But maybe it's more complex than that.  

If you talk to American doctors about Giant Cell Tumors.  They relate those to bones, not joints.  And just like with PVNS, most cases are found in the knee.  But is PVNS really a giant cell tumor?  The answer is yes.  According to research I have done and doctors who have released information, PVNS falls under the umbrella of TGCT. So the Europeans are correct in calling it TGCT.  But they really should recognize the different variations of TGCT as PVNS really tends to effect the lower extremities such as the knees, hips, and ankles.  In a more recent publication a doctor had refereced TGCT of the tendon sheath saying, 

"Histochemical evidence shows that the mononuclear cells and giant cells present in these lesions resemble osteoclasts, ^[14, 15] and this resemblance suggests a bone marrow–derived monocyte/macrophage lineage for these tumors. Polymerase chain reaction (PCR) assays have shown that giant cell tumors of the tendon sheath are polyclonal proliferations, ^[16] which suggests that these masses are nonneoplastic proliferations, if one accepts the premise that a population of cells forming a tumorous mass must show clonality to be classified as a neoplasm."

Recurrences were all over the place.  Doctors reporting anywhere from a 9% to a 44% recurrance after surgery.  Those numbers don't show any concept of what sufferers can expect.  In fact there really hasn't been a new survey done on how many people have PVNS since 1980.   The biggest concern from doctors is that TGCT or PVNS will cause degenerative bone disease.  And as anyone with a record of multiple surgeries knows that eventually you do need to replace the affected joint. 

The idea of radiotherapy is popular amongst some doctors and there are clinical trials but to date a surgical procedure is the favorite to remove the lesions growing in the joint.   There is no cure and the disease is still rare enough that many doctors are not aware of it.  Especially when there are multiple names.  So although PVNS does fall under the category of TGCT it would be like saying instead of having cancer you have TGCT.  People would be confused if suddenly TGCT was the way to describe having cancer.  And although there are very few cases of PVNS being or becoming malignant it's safe to say that PVNS is commonly benign.  I still am not interested in calling my PVNS anything other than PVNS since I don't want to give the impression that it could be cancer.