Surgical Pathology Criteria–

Superficial Acral (Digital) Fibromyxoma

Differential Diagnosis

 

Superficial Acral Fibromyxoma Acquired Digital Fibrokeratoma
May be keratotic but lacks developed horn Usually has a keratotic horn
Forms a dermal nodule More exophytic lesion
Usually infiltrates surrounding and underlying tissues Circumscribed
Moderate cellularity Hypocellular collagen
Frequently increased vascularity No increased vascularity
Myxoid and collagenous stroma Fibrotic collagenous stroma
EMA may be positive EMA negative

 

Superficial Acral Fibromyxoma Periungual and Subungual Fibroma
Forms a dermal nodule More exophytic lesion, frequently filiform or verrucous
Moderate cellularity No increase in cellularity
Frequently increased vascularity No increased vascularity

 

Superficial Acral Fibromyxoma Superficial Angiomyxoma
Neutrophils uncommon Neutrophils common
Epithelial component rare Frequent epithelial component
Prominent fibrous component mixed/alternating with moderately cellular myxoid areas Predominant hypocellular myxoid component, frequently in pools
EMA variably positive EMA negative

 

Superficial Acral Fibromyxoma Dermal Mucinosis
Moderately cellular Markedly hypocellular
Frequent capillary proliferation Hypovascular
Frequent fibrotic component Purely myxoid

 

Superficial Acral Fibromyxoma Neurofibroma
Alternating myxoid and collagenous areas Random, disorganized pattern
S100 negative S100 positive

 

Superficial Acral Fibromyxoma Sclerosing Perineurioma
Random, fascicular or loose storiform patterns Typically has concentric, onion bulb pattern
CD34 positive CD34 negative
Note: Lesions described as subungual perineuriomas are probably the same lesion as superficial acral fibromyxoma

 

Superficial Acral Fibromyxoma Dermatofibrosarcoma Protuberans
Virtually all acral Usually central, rarely acral
Loose storiform or random pattern Usually has some classic non-myxoid areas with tight storiform
EMA may be positive EMA negative
Apolipoprotein D negative (0/4) Apolipoprotein D positive (90%)
No consistent cytogenetic abnormality t(17;22)

 

Superficial Acral Fibromyxoma Low Grade Fibromyxoid Sarcoma
Virtually all acral Most in deep soft tissues, rarely acral
CD34 usually strong, MUC4 negative CD34 negative to rare faint, MUC4 positive
No mutations involving FUS gene t(7:16) or t(11:16)

 

Superficial Acral Fibromyxoma Cellular Myxoma
Virtually all acral Most in deep soft tissues, rarely acral
No GNAS1 mutations GNAS1 activating mutations

 

Superficial Acral Fibromyxoma Inflammatory Myxohyaline Tumor of Distal Extremities
Virtually all superficial Usually deep
Usually one nodule Usually multinodular
Lacks inflammation Abundant inflammation
Cytologically bland and uniform Reed-Sternberg like cells
May be EMA positive EMA negative

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