Juxtaarticular Myxoma
Khin Thway, BSc, MBBS, FRCPath
Key Facts
Terminology
Benign lesion occurring in region of large joints, with histologic features of myxoma
Etiology/Pathogenesis
Some associated with trauma or occur adjacent to osteoarthritic joint
Clonal chromosomal abnormalities in 1 case suggest that some lesions may be neoplastic
Clinical Issues
90% occur around knee joint
Local recurrence in a proportion of cases
Microscopic Pathology
Bland spindle or stellate fibroblast-like cells
Hypovascular myxoid stroma
Cystic spaces present in many
Mitotic figures rare or absent
 In this juxtaarticular myxoma, the lesion is circumscribed and composed of spindle to stellate fibroblast-like cells that are small and bland, within abundant myxoid stroma. |
 The lesion varies from sparsely cellular (right) to paucicellular (left). The cells are embedded in patternless distributions within stroma that is myxoid and hypovascular. |
TERMINOLOGY
Abbreviations
Juxtaarticular myxoma (JAM)
Definitions
Benign lesion occurring in region of large joints, histologically similar to intramuscular myxoma
ETIOLOGY/PATHOGENESIS
Environmental Exposure
Lesions have been associated with trauma
May also occur adjacent to osteoarthritic joint
Genetic Abnormality
Clonal chromosomal abnormalities shown by cytogenetic analysis in 1 case
Suggests that some lesions may be neoplastic rather than reactive
CLINICAL ISSUES
Epidemiology
Age
Adults
Predominantly 3rd-5th decades
Gender
M > F
Site
Occurs adjacent to large joints
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