superficial acral fibromyxoma

Definition: Superficial acral fibromyxoma (SAF) is a newly characterised soft tissue tumour of the hands and feet with a tendency to involve the nail region.

Images

 superficial acral fibromyxoma

• https://twitter.com/DanglisFotiosMD/status/798122611377049601
• - https://twitter.com/LinskeyKaty/status/733018339065401344

Digital fibromyxoma (first described by Fetsch and colleagues as "superficial acral fibromyxoma") is a distinctive soft tissue tumor with a predilection for the subungual or periungual region of the hands and feet.

Clinical features

 Adults (range 14 to 72 years, median 46 years).
 M:F=2:1.
 Site: great toe, other toes; fingers;palm; nail region.
 The lesions are generally slow-growing and painless.

Macroscopy

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

Micrsocopy

 The lesions are dermal or subcutaneous.
 A few involve fascia or periosteum.
 Cellularity is moderate, consisting of stellate or spindled fibroblast-like cells in a myxoid, myxocollagenous or collagenous matrix.
 A storiform pattern is seen.
 Multinucleate cells are present.
 Some tumors show moderate or pronounced nuclear pleomorphism.
 Some tumors show mitoses, up to 7 per 50 HPF.
 Most cases contain mast cells and some a mild lymphocytic infiltrate.
 The margins are pushing or infiltrative.

IHC

 CD34+
 S100-

Differential diagnosis

See: Differential diagnosis of cutaneous myxoid lesions or 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 pattern
• 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 perineurioma:

• 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 fibrokeratoma (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 fibroma/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.

Molecular biology

Sequencing of 8 digital fibromyxomas failed to reveal mutations in exon 8 or 9 of GNAS1, in contrast to intramuscular or cellular myxoma. (22367301)

Management

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

Prognosis

 May recur locally. No metastases reported.

See also

 myxoid tumors

• cutaneous myxoid tumors

 acral tumors

References

 Digital Fibromyxoma (Superficial Acral Fibromyxoma): A Detailed Characterization of 124 Cases. Hollmann TJ, Bovée JV, Fletcher CD. Am J Surg Pathol. 2012 Feb 24. PMID: 22367301

 Meyerle JH, Keller RA, Krivda SJ. Superficial acral fibromyxoma of the index finger. J Am Acad Dermatol. 2004 Jan;50(1):134-6. PMID: 14699384

 Kazakov DV, Mentzel T, Burg G, Kempf W. Superficial acral fibromyxoma: report of two cases. Dermatology. 2002;205(3):285-8. PMID: 12399679

 Fetsch JF, Laskin WB, 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 Jul;32(7):704-14. PMID: 11486169