Angiomatoid Fibrous Histiocytoma

Definition

Predominantly superficial tumor usually containing cystic blood filled spaces and having a prominent peripheral lymphoid infiltrate

Circumscribed subcutaneous mass
- May have a fibrous capsule
- Rare cases may involve skeletal muscle or periosteum
- Rare cases centered in dermis
Sheets and short fascicles of bland round to short spindled cells
- Usually arranged in nodules
- May have epithelioid, histiocytoid or myoid appearance
- Occasionally contains areas of moderately atypical cells
- Faintly eosinophilic cytoplasm
- Infrequent mitotic figures
- May have occasional foam cells
Large blood filled cystic spaces in most cases
- Lined by lesional round to spindled cells, not by endothelial cells
- May also have dilated endothelial lined vascular spaces
- May thrombose
Marked peripheral lympho-plasmacytic infiltrate
- May form germinal centers
- Present in 80-90% of cases
- May resemble a lymph node, often in a location where there should not be one
  - Lacks subcapsular sinus and hilar lymphatics
90% <30 years of age
Infrequent/rare findings
- Multinucleated cells
- Calcifications
- Palisaded stromal nuclei
- Marked pleomorphism (no clinical significance)
- Higher mitotic rate >5/10 hpf (no clinical significance)
- Focal and less frequently extensive myxoid change in stroma
  - May produce reticular pattern (interanastomosing cords and strands of cells)

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

Original posting; last update: 8/10/08, 7/19/15