Inflammatory Myxohyaline Tumor of Distal Extremities

Definition

Neoplasm containing myxoid and hyalinized areas with a prominent inflammatory infiltrate and cells with large bizarre nuclei

Multinodular
- Infiltrates subcutaneous fat
- Rarely may infiltrate into synovium, dermis or underlying muscle
Myxoid nodules with a surrounding cellular to hyalinized stroma
- Hemosiderin may be present
Scattered large atypical cells may resemble virocytes or Reed-Sternberg cells
- Short spindled to epithelioid cells
- Large vesicular nuclei
  - May be markedly pleomorphic
  - Prominent inclusion-like nucleoli
  - May be binucleate or multinucleated
- Abundant eosinophilic cytoplasm
  - Homogeneous to vacuolated
  - Vacuoles may indent nuclei
  - May have cells resembling lipoblasts or ganglion cells
- May show emperipolesis of inflammatory cells
Few mitotic figures
- May be atypical
Extensive inflammatory infiltrate
- Lymphocytes, eosinophils, plasma cells, histiocytes primarily in solid areas
- Neutrophils primarily in myxoid areas
Located on extremities, usually distal

Richard L Kempson MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342