Intramuscular Myxoma
Differential Diagnosis
- Aggressive angiomyxoma
- Myxoid neurofibroma
- Low grade fibromyxoid sarcoma
- Myxoid liposarcoma
- Low grade myxofibrosarcoma
- Cellular myxoma
- Juxta-articular myxoma
- Nodular fasciitis
| Intramuscular Myxoma | Aggressive Angiomyxoma |
|---|---|
| Frequently on extremities | Perineal or pelvic |
| Hypovascular | Prominent medium to large vessels |
| Myxoid Neurofibroma | Intramuscular Myxoma |
|---|---|
| May involve nerve | No nerve involvement |
| S100 positive | S100 negative |
| Low Grade Fibromyxoid Sarcoma | Intramuscular Myxoma |
|---|---|
| Alternating fibrous and myxoid patterns | Uniform myxoid pattern |
| Swirling, whorled pattern | No swirling, whorled pattern |
| Myxoid Liposarcoma | Intramuscular Myxoma |
|---|---|
| Arborizing vascular pattern | Hypovascular |
| Lipoblasts present, usually signet ring type | No lipoblasts |
| More cellular | Extremely paucicellular |
| Myxofibrosarcoma | Intramuscular Myxoma and Juxta-articular Myxoma |
|---|---|
| Pleomorphism present | Uniformly small bland cells |
| More cellular | Extremely paucicellular |
| Mitotic figures may be present | Mitotic figures practically never present |
| Arching vessels | Markedly hypovascular |
| Cellular Myxoma | Intramuscular Myxoma |
|---|---|
| Moderate cellularity must comprise at least 20% of lesion | Markedly hypocellular |
| Arching vessels may be present | Markedly hypovascular |
| May have areas of collagenous stroma | Uniformly myxoid stroma |
| Juxta-articular Myxoma | Intramuscular Myxoma |
|---|---|
| Adjacent to large joint | Intramuscular |
| May be more cellular | Extremely paucicellular |
| Lacks Gs(alpha) mutation | Gs(alpha) mutation frequent |
| Intramuscular Myxoma | Nodular Fasciitis |
|---|---|
| Very hypocellular | Moderately cellular |
| No grouping of cells | Undulating bundles of cells |
| No tissue culture appearance | Tissue culture appearance with tears and spaces in tissue |
| Rare mitotic figures | Frequent mitotic figures |
