Dermatofibrosarcoma Protuberans

Differential Diagnosis

Dermal and Deep Fibrous Histiocytoma	Dermatofibrosarcoma Protuberans
Usually <1 cm	Frequently >2 cm
Haphazard short fascicles in dermal lesions; deep lesions frequently storiform	Regular storiform pattern
Infrequent infiltration into and around fat cells	Frequent infiltration into and around fat cells
Frequently mixed cell population	Monomorphous cell population
Frequent overlying epithelial hyperplasia	Overlying epithelium usually attenuated
CD34 40% in deep lesions, negative in dermal lesions	CD34 100% extensive
Apolipoprotein D negative (deep lesions not tested)	Apolipoprotein D 90%
Factor XIIIa >95% extensive	Factor XIIIa 75% but focal and weak

CD34 and Factor XIIIa are difficult to interpret in many cases because of numerous entrapped reactive cells

Myxoid Nerve Sheath Tumor	Myxoid Dermatofibrosarcoma Protuberans
Areas of typical nerve sheath tumor usually present	Areas of typical storiform pattern usually present
S100 positive	S100 negative
CD34 may stain scattered dendritic cells but not lesional cells	CD34 stains lesional cells

Myxoid Liposarcoma	Myxoid Dermatofibrosarcoma Protuberans
Usually involves deep soft tissue	Usually involves dermis and superficial subcutaneous tissue
Frequently contains lipoblasts	No lipoblasts
CD34 may stain scattered dendritic cells but not lesional cells	CD34 stains lesional cells

Plexiform Fibrous Histiocytoma	Dermatofibrosarcoma Protuberans
Ray-like extension into surrounding fat	Infiltrates between and around individual fat cells
Collagenous stroma	Usually contains only fine collagen
Nodules of histiocytes and giant cells in most cases	Histiocytes and giant cells very rare
CD34 negative	CD34 stains lesional cells

Desmoplastic Melanoma	Dermatofibrosarcoma Protuberans
Lacks storiform pattern	Prominent storiform pattern
Displaces or destroys fat	Infiltrates between and around individual fat cells
Dense collagenous stroma	Usually contains only fine collagen
Frequently contains lymphoid nodules	Inflammatory cells infrequent
CD34 negative	CD34 stains lesional cells
S100 positive	S100 negative

Dermatofibrosarcoma Protuberans	Adult or Infantile Fibrosarcoma
CD34 positive	CD34 negative
Storiform pattern	Fascicular, herringbone pattern
Involves dermis and subcutaneous tissue	Virtually always in deep soft tissue

DFSP may dedifferentiate with a fibrosarcoma pattern
If fibrosarcoma occurs in the dermis or subcutaneous tissue, it is usually dedifferentiated DFSP