Deep Fibrous Histiocytoma
Definition
- Neoplasm with features of usual dermal fibrous histiocytoma but occuring in subcutaneous or deep soft tissue
Alternate / Historical Names
-
Deep benign fibrous histiocytoma
Diagnostic Criteria
- Must have at least areas of histologic features of usual dermal fibrous histiocytoma
- Spindled to plump ovoid cells
- Indistinct cytoplasm
- Bland cytology
- Vesicular nuclei with small nucleoli
- Storiform pattern
- (Differs from dermal fibrous histiocytoma)
- May also have areas of short fascicles
- Variable numbers of interspersed lymphocytes
- May also have foam cells and multinucleated giant cells
- Located in subcutaneous tissue (91%) or deep visceral soft tissue (9%)
- May be attached to fascia or tendon
- Well circumscribed
- Frequently with fibrous pseudocapsule
- Mitotic figures range from 0-66/10 hpf
- Median 3/10 hpf
- Variable features
- Staghorn blood vessels 42%
- (Differs from dermal fibrous histiocytoma)
- Focal stromal hyalinization 39%
- Myxoid stroma 9%
- Peripheral lymphoid infiltrate
- May form germinal centers
- Hemorrhage and or hemosiderin
- May be aneurysmal
- Cystic degeneration
- Infarction
- Staghorn blood vessels 42%
- Rare findings
- Metaplastic ossification (1/69 cases)
- Vascular invasion (1/69)
- Rare cases with features of atypical fibrous histiocytoma (6/69 cases)
- Scattered large pleomorphic cells
- Bizarre hyperchromatic or vesicular nuclei
- Prominent nucleoli
- Pleomorphic nuclei also seen in foam cells and multinucleated cells
- Atypical mitotic figures
- Tumor cell necrosis
- Note that this was not considered a criterion for atypical fibrous histiocytoma in the publication of Gleason 2008, but one of their two cases with tumor cell necrosis metastasized.
- Scattered large pleomorphic cells
- (Only one up to date published series Gleason 2008)
Richard L Kempson MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting:August 10, 2008
Last update: December 30, 2008
