Most arise at dermal-subcutaneous interface
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Also lower extremity, trunk, head, and neck
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Painless, slow-growing mass or plaque
•
Treatment: Wide surgical excision with negative margins
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Local recurrence in up to 40%
•
Low metastatic potential (6%)
Macroscopic
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Multinodular, poorly delineated, tan-white
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Usually < 3 cm (range: 0.3-8.5 cm)
Microscopic
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Poorly circumscribed with infiltrative growth pattern
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Morphologically subdivided into 3 types (fibroblastic, histiocytic, mixed)
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Fascicles of spindled fibroblastic cells
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Nodules or aggregates of epithelioid histiocytoid cells
Osteoclast-like giant cells common
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Multinodular and plexiform growth
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Low mitotic rate; usually no cellular pleomorphism
Ancillary Tests
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(Myo)fibroblasts SMA(+); histiocytes CD68(+) and CD163(+)
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Negative for S100, CD34, desmin, keratin, MITF
Top Differential Diagnoses
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Giant cell tumor of soft tissue
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Low-grade myofibroblastic sarcoma
TERMINOLOGY
Abbreviations
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Plexiform fibrohistiocytic tumor (PFHT)
Synonyms
•
Plexiform fibrous histiocytoma
Definitions
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Rarely metastasizing dermal-subcutaneous mesenchymal neoplasm composed of variable mixture of fibroblasts and histiocyte-like cells
CLINICAL ISSUES
Epidemiology
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Incidence
Rare
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Age
Most common in children and young adults
–
Overall wide range: 1-77 years
•
Sex
Male = female
–
Female predilection in some series
Site
•
Upper extremity (particularly forearm and hand)
•
Also lower extremity, trunk, head and neck
•
Most arise at dermal-subcutaneous interface
May also be purely dermal or subcutaneous
–
Subcutaneous tumors may involve skeletal muscle
Presentation
•
Painless, slow-growing mass or plaque
Treatment
•
Wide surgical excision or reexcision with negative margins
•
Examination of regional lymph nodes may be warranted
•
Indefinite clinical follow-up recommended