Superficial acral fibromyxoma

This is a newly characterised soft tissue tumour of the hands and feet with a tendency to involve the nail region. The information below is based on 37 cases.

Clinical features

Adults (range 14 to 72 years, median 46 years). M:F=2:1.

Site: great toe;12, other toes;8, fingers;13, palm; 4. 16 cases involved the nail region. The lesions were generally slow-growing and painless.

Macroscopic appearances

The tumours ranged from 0.6 to 5.0 cm (median 1.5 cm). They were soft to firm with a gelatinous or solid off-white cut surface.

Histopathology

The lesions were dermal or subcutaneous and a few involved fascia or periosteum. Cellularity was moderate, consisting of stellate or spindled fibroblast-like cells in a myxoid (n=19), myxocollagenous (n=11) or collagenous (n=7) matrix. A storiform pattern was see. Multinucleate cells were present (n=19). Five tumours showed moderate or pronounced nuclear pleomorphism. Five tumours showed mitoses, up to 7 per 50 HPF. Most cases contained mast cells and some a mild lymphocytic infiltrate. The margins were pushing (n=22) or infiltrative (n=15).

Immunohistochemistry

CD34 21/23 EMA 18/25 CD99 11/13 S-100 1/23 HMB-45 0/?27 SMA 0/?27 muscle-specific actin 0/?27 desmin 0/?27 GFAP 0/?27 Keratins (AE1/AE3, LP34) 0/?27 (rare entrapped fibrous cells stained)

Ultrastructure

Differential diagnosis

See: Differential diagnosis of cutaneous and subcutaneous myxoid lesions

• Fibrous histiocytoma variant: abundant myxoid matrix rare, more storiform, more stellate interface with normal stroma, CD34 negative.

• Dermatofibrosarcoma protuberans: rare on extremities, may contain abundant myxoid stroma, CD34 positive, but usually retain foci of tight storiform architecture, have a more infiltrative growth patter and lack EMA immunoreactivity.

• cutaneous myxoma (superficial angiomyxoma): weakly linked to Carney complex, abundant stromal mucin forming pools with peripheral acellular cleftlike spaces. May be CD34 positive.

• Sclerosing perineuroma: strong predilection for fingers and palms of young adults, abundant dense collagen, cords and onion-bulb pattern of small epithelioid and spindled cells, EMA positive but CD34 negative.

• Acquired (digital) fibrokeratoma:

  • classical (type 1); smaller, more superficial, more exophytic, less cellular, less vascular, collagen in parallel bundles

  • variant (type 2); more closely resemble acral fibromyxoma, being more cellular with less well organised collagen and a storiform pattern, but are more superficial and have minimal myxoid matrix.

• Periungual/subungual fibroma of tuberous sclerosis (Koenen tumour): multifocal, polypoidal/verrucous, fibrous connective tissue, less cellular.

• Acral myxoinflammatory fibroblastic sarcoma (inflammatory myxohyaline tumour of the distal extremities with virocyte or Reed-Sternberg-like cells): peak incidence in midadult life, predilection for extremities, subcutis and deep soft tissues, multinodular with poorly defined margins, stellate and spindled cells with large pleomorphic nuclei and inclusion-like nucleoli, substantial mixed inflammatory component, EMA negative, may be CD34 positive.

Management

Complete excision, in view of uncertain behavior, especially in the cases with pleomorphism or mitoses.

Prognosis

May recur locally. No metastases reported.

References

Fetsch, J. F., Laskin, W. B., Miettinen, M. Superficial acral fibromyxoma: a clinicopathologic and immunohistochemical analysis of 37 cases of a distinctive soft tissue tumor with a predilection for the fingers and toes. Hum Pathol 2001;32:704-714.

This page last revised 8.11.2001.