Superficial Acral (Digital) Fibromyxoma
Definition
- Superficial spindle cell lesion with myxoid and fibrous stroma, typically located in acral sites
Diagnostic Criteria
- Vast majority are subungual or periungual, on either fingers or toes
- Very rare cases located on ankle and leg
- Superficial lesion with frequent infiltration of dermal collagen and fat
- Frequently extends into subcutaneous tissue
- May erode or infiltrate underlying bone
- Perineural invasion not seen
- Overlying epidermis may be keratotic, but typically not a cutaneous horn
- Moderate cellularity with spindled and stellate cells
- Minimal atypia
- Occasional large degenerate nuclei and multinucleated cells
- Mitotic figures rare
- No necrosis or pleomorphism
- Mast cells frequent
- Neutrophils infrequent unless ulcerated
- Usually a mixture of myxoid stroma and areas of dense hyaline collagen
- May create an alternating pattern
- Occasionally one pattern predominates
- Myxoid areas are Alcian blue positive
- Infrequently may show cartilaginous or osseous metaplasia
- One report of fatty metaplasia
- Capillary proliferation may be prominent in myxoid areas
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting/updates:: 3/24/12
