Juxta-articular
myxoma is a rare myxoid
tumor of soft tissue that bears a close histologic resemblance to intramuscular
myxoma but is distinguished from the latter by its clinical setting and behavior. Activating missense mutations at the Arg 201
codon of the Gs alpha gene ultimately leading to increased levels of cyclic
adenosine monophosphate have been implicated in
McCune-Albright syndrome and sporadic
fibrous dysplasia of bone. Recently, we have demonstrated that the same Gs alpha mutations occur in intramuscular
myxomas associated with
fibrous dysplasia of bone (Mazabraud's syndrome) as well as in sporadic intramuscular
myxoma. The overlapping histologic appearances of juxta-articular
myxoma and intramuscular
myxoma prompted us to investigate whether there is a relationship between the two entities. We studied this possibility by looking for Gs alpha mutations in juxta-articular
myxoma using polymerase chain reaction (PCR) to amplify appropriate genomic
DNA fragments extracted from
formalin-fixed,
paraffin-embedded specimens of five juxta-articular
myxomas, followed by single-strand conformation polymorphism analysis. Using these techniques, no aberrant bands were detected in any of the five juxta-articular
myxomas, indicating that they lack Gs alpha mutations. Moreover,
DNA sequencing of the PCR products of two JAMs showed no abnormalities. We conclude that juxta-articular
myxomas, in contrast to intramuscular
myxomas, do not involve Arg 201 mutations of the Gs alpha gene, indicating that they represent distinct entities with different underlying molecular mechanisms.