Dermatofibrosarcoma Protruberans (DFSP)

Epidemiology:

Common sites:

• trunk

Gross features:

• aggregated, protruberant tumour within a firm, indurated plaque
• may ulcerate

Histologic features:

• infiltrative border
• extension into subcutaneous fat
• characteristic “honeycomb” pattern
• cellular
• storiform/pinwheel pattern
• short interlacing fascicles
• mitoses usually present
• thinning of overlying epidermis
• fibrosarcoma transformation:
• herringbone pattern (fascicles at sharp angles to each other)
• collagen deposition

Immunophenotype:

Marker:	Sensitivity:	Specificity:
CD34
Factor XIIIa (neg)

Molecular features:

Other features:

• may transform into fibrosarcoma with more malignant behaviour
• look for CD34 negativity