Pleomorphic Hyalinizing Angiectatic Tumor

Definition

Mitotically inactive tumor composed of large bizarre cells with prominent ectatic vessels

Large spindled and epithelioid cells
- Bizarre hyperchromatic nuclei
- Frequent intranuclear inclusions
- Abundant eosinophilic cytoplasm
- Frequently contain hemosiderin
- May contain pale cytoplasmic globules
Prominent large thin walled vessels
- Frequently clustered
- Fibrin in and around vessel walls
Stroma frequently hyalinized
Microscopically infiltrative borders
- Predominantly subcutaneous, may involve dermis
- Dermal lesions may surround skin adnexae
Mitotic figures very rare
Early lesion pattern
- Short fascicles of bland spindled cells
  - Hemosiderin in cells
  - Infiltrates fat
  - Aggregates around groups of small blood vessels
- Rare pleomorphic cells present
- Small blood vessels focally ectatic with fibrin
- Frequent myxoid matrix
- Early features may be seen adjacent to classic pattern
- Proposed to be equivalent to hemosiderotic fibrohistiocytic lipomatous lesion

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