Superficial Acral Fibromyxoma

 Particularly in or near nail bed



• Solitary, slowly growing, and often long-standing lesion

• Treatment: Complete excision

• Excellent prognosis

• Low rate of recurrence, usually related to incomplete excision




Macroscopic




• Usually < 5 cm (median: 1.5 cm)


Microscopic




• Moderately cellular proliferation of spindled to stellate fibroblastic cells in randomly arranged loose fascicles or storiform arrays

• Nuclear atypia minimal to absent

• Rare mitoses; no necrosis

• Variable myxoid, myxocollagenous, or collagenous stroma

• Mast cells common


Ancillary Tests




• CD34(+)

• Negative for S100, desmin, keratin, claudin-1


Top Differential Diagnoses




• Dermatofibroma (fibrous histiocytoma)

• Perineurioma

• Acquired digital fibrokeratoma

• Dermatofibrosarcoma protuberans

• Myxoid neurofibroma

image
SAF
Superficial acral fibromyxoma (SAF), also referred to as digital fibromyxoma, is a benign fibroblastic tumor that shows a marked predilection for the fingers and toes, particularly the nail bed region. Histologically, it is characterized by bland spindled and stellate cells arranged in random loose fascicles and storiform arrays within a variable myxoid to fibrous stroma.


image
Prominent Collagen in SAF
Some areas of SAF feature prominent stromal collagen, as depicted.

image
Loose Storiform Growth in SAF
SAF may also demonstrate a loose arrangement of cells in a more vascularized stroma, somewhat resembling perineurioma. Despite its usual dermal origin, in some cases, SAF shows superficial extension into subcutaneous fat image.

image
CD34 Expression in SAF
CD34 expression is seen in most cases of SAF, but the extent of this positivity varies. Focal EMA and SMA may also be seen in rare cases. S100, claudin-1, desmin, and keratins are negative.


TERMINOLOGY


Abbreviations




• Superficial acral fibromyxoma (SAF)


Synonyms




• Acral fibromyxoma

• Digital fibromyxoma

• Cellular digital fibroma


Definitions




• Benign fibroblastic neoplasm that occurs in hands and feet, particularly nail bed region


CLINICAL ISSUES


Epidemiology




• Incidence
image Rare

• Age
image Wide age range
– Most common > 40 yr

• Sex
image Male predilection


Site




• Almost exclusively on hands and feet
image Vast majority in fingers and toes

– Particularly subungual or periungual region (nail bed)

• Extremely rare in nonacral sites


Presentation




• Solitary, slowly growing, and often longstanding lesion
image Associated with pain in up to 40-50% of cases

• Superficial, dermal based


Treatment




• Complete excision

Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Superficial Acral Fibromyxoma
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