Soft tissue

Fibroblastic / myofibroblastic

Superficial acral fibromyxoma


Editorial Board Member: Jose G. Mantilla, M.D.
Deputy Editor-in-Chief: Borislav A. Alexiev, M.D.
Saira Fatima, M.B.B.S.
Nasir Ud Din, M.B.B.S.

Last author update: 11 March 2024
Last staff update: 11 March 2024

Copyright: 2002-2024, PathologyOutlines.com, Inc.

PubMed Search: Superficial acral fibromyxoma

Saira Fatima, M.B.B.S.
Nasir Ud Din, M.B.B.S.
Page views in 2024 to date: 5,223
Cite this page: Fatima S, Ud Din N. Superficial acral fibromyxoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissuesuperficialacral.html. Accessed April 15th, 2024.
Definition / general
  • Benign neoplasm of fibroblastic origin, with tendency for affecting periungual regions of the digits on acral sites
  • Lesions are prone to local recurrence
Essential features
  • Acral region especially around the digits are favored sites
  • Lobulated dermal and subcutaneous spindle cell lesion with myxoid and collagenous stroma
  • Stroma and prominent vessels
  • RB1 gene deletions are observed
  • Surgical excision with adequate margins is treatment of choice
Terminology
  • Acceptable: digital fibromyxoma, superficial acral fibromyxoma
  • Not recommended: cellular digital fibroma
ICD coding
  • ICD-O: 8811/0 - fibromyxoma
  • ICD-11: EE6Y & XH8173 - other specified fibromatous disorders of skin and soft tissue & acral fibromyxoma
Epidemiology
Sites
Pathophysiology
Etiology
  • Unknown
Clinical features
Diagnosis
  • Acral soft tissue lesion affecting digits with or without cortical erosion
  • Typical location around digits should raise clinical suspicion
  • Radiological features are not characteristic
  • Histological examination of the lesion is diagnostic
  • Reference: J Cutan Pathol 2008;35:1020
Radiology description
  • Plain radiograph (Skeletal Radiol 2008;37:499)
    • Well circumscribed soft tissue mass with secondary saucer-like erosion of bone cortex
    • Calcification is absent
    • There may be sclerosis and buttressed margin of cortex in longstanding cases
  • Magnetic resonance imaging (MRI): soft tissue lesion, T2 hyperintense with focal thinning of the cortex (Skeletal Radiol 2008;37:499)
Radiology images

Contributed by Nasir Ud Din, M.B.B.S.
AP Xray distal phalanx

AP Xray of distal phalanx



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Plain Xray

MRI

MRI

CT and MRI

Computed tomography (CT) and MRI

Prognostic factors
  • Local recurrences developed in 3 of 14 patients (22%) in a study (J Cutan Pathol 2008;35:1020)
  • In a study of 18 patients (mean follow up interval of 10.1 years), there was 1 recurrence after local excision and 2 cases persisted / progressed after partial excision (Hum Pathol 2001;32:704)
  • Local recurrence was seen in 24% of cases in another study (all near the nail unit of the fingers or toes) after a mean interval of 27 months (Am J Surg Pathol 2012;36:789)
    • 1 tumor recurred twice
    • Margins on initial biopsy or subsequent excision had been involved
    • No other clinical or pathologic features were predictive of recurrence / persistence
  • Metastasis has not been reported
Case reports
Treatment
  • Surgical excision with adequate margin is recommended
  • Locally recurrent lesions can undergo re-excision
Clinical images

Contributed by Jose G. Mantilla, M.D.
Well circumscribed periungual mass

Well circumscribed periungual mass



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Retronychia of toe

Retronychia of toe

Subungual round tumor, green nail plate

Subungual round tumor, green nail plate

Subungual round pinkish tumor

Subungual round pinkish tumor

Subungual tumor distorting nail plate

Subungual tumor distorting nail plate

Dermoscopy

Dermoscopy

Gross description
Gross images

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Nodules with firm consistency

Nodules with firm consistency

Soft lobulated lesion

Soft lobulated lesion

Nodular pink mass

Nodular pink mass

Microscopic (histologic) description
  • Poorly circumscribed lesion in dermis composed of spindle to stellate shaped fibroblastic cells arranged in a loose storiform / fascicular pattern with alternating myxoid and collagenous stroma (Am J Surg Pathol 2012;36:789)
  • Microvasculature is prominent (Hum Pathol 2001;32:704)
  • Multinucleated stromal cells may be present and mast cells are frequent (Hum Pathol 2001;32:704)
  • Bland nuclei lacking significant mitoses or necrosis; occasionally degenerative atypia may be encountered
  • Infiltration in adipose tissue can occur
  • Cellular variants are also encountered
  • Cartilaginous and osseous metaplasia may be observed
Microscopic (histologic) images

Contributed by Nasir Ud Din, M.B.B.S.
Polypoid acral skin lesion

Polypoid acral skin lesion

Acral skin lesion

Acral skin lesion

Spindle cell lesion

Spindle cell lesion

Giant cells

Giant cells

Storiform pattern

Storiform pattern

Cellular region

Cellular region


CD34 stain

CD34 stain

Cytology description
  • Oval to spindle cells with bland nuclear chromatin with background mucoid / myxoid material
  • Groups and cohesive clusters of spindle cells with scattered thin walled capillaries (J Cytol 2015;32:39)
Cytology images

Images hosted on other servers:
Myxoid matrix with bland spindle cells

Myxoid matrix with bland spindle cells

Positive stains
Negative stains
Electron microscopy description
Molecular / cytogenetics description
  • Deletion of the RB1 gene is detected but not required to establish the diagnosis
Videos

Superficial acral fibromyxoma

Sample pathology report
  • Left big toe, excision biopsy:
    • Acral fibromyxoma (see comment)
    • Comment: There is a well circumscribed dermal based spindle cell neoplasm comprised of collagenous and myxoid areas. The stellate cells are bland, lacking atypia. Mitoses are rare. There is prominent thin vasculature. Scattered mast cells are noticed. Immunohistochemical stains for CD34 and CD99 are positive in spindle cells; features are consistent with superficial acral fibromyxoma, a benign fibroblastic tumor. The tumor is completely excised. Local recurrence is uncommon following complete excision.
Differential diagnosis
  • Onychomatricoma:
    • Rarely affects nail matrix
    • Spindle shaped stromal cells with epithelial component
    • CD34 is positive
  • Myxoid neurofibroma:
    • Spindle cells with wavy nuclei in abundant myxoid stroma
    • Prominent vasculature is lacking
    • S100 and CD34 positive
  • Superficial angiomyxoma:
    • Occurs anywhere in the body, mostly affecting the head and neck region
    • Multilobulated tumor in dermis and subcutis with infiltrative growth
    • Myxoid matrix is abundant
    • Arborizing vessels are prominent at edges
    • Intralesional neutrophils
    • SMA is negative
    • CD34 is negative
  • Acral fibrokeratoma:
    • Polypoid dome shaped
    • Dense collagenous stroma, mature spindle cells and small vessels
    • Vertical orientation of collagen fibers
  • Dermatofibrosarcoma protuberans (DFSP):
    • Affecting trunk and extremities
    • Myxoid DFSP is rare in digits
    • Storiform pattern and deep infiltration in the subcutaneous fat
    • CD34 is positive
  • Fibroma of tendon sheath:
    • Well circumscribed, attached to tendon
    • Sparsely cellular
    • Spindle cells in fibrous stroma
    • Vessels are slit-like
    • SMA is positive
    • CD34 is negative
  • Giant cell tumor of tendon sheath:
    • Lobulated, gray-brown
    • Attached to tendon sheath
    • Spindle, epithelioid and giant cells in fibrous stroma
    • Hemosiderin and foamy cells along with inflammatory cells in varying proportion
    • CD34 is negative
    • CD68 is positive
  • Glomus tumor:
    • Solitary painful mass of digits involving subcutaneous
    • Uniform round to polygonal cells arranged around vessels
    • SMA is positive
    • CD34 is negative
Board review style question #1

A 30 year old woman presented with a slow growing painless subungual mass. Plain Xray revealed uninvolved bone. Magnetic resonance imaging (MRI) confirmed a soft tissue confined lesion without bone erosion. Excision specimen revealed histological features as shown in the given image. Which positive IHC stain helps confirm the diagnosis?

  1. CD34
  2. Desmin
  3. MUC4
  4. S100
  5. SMA
Board review style answer #1
A. CD34. In superficial acral fibromyxoma (SAF), only CD34 will be diffuse and strongly positive. Answer E is incorrect because SMA is only focally positive and is not diagnostic, as it can be positive in many other spindle cell lesions. Answer D is incorrect because S100 is negative in SAF and will exclude nerve sheath tumor. Answer B is incorrect because desmin negativity excludes rhabdoid differentiation. Answer C is incorrect because MUC4 will be negative in SAF, which is a positive marker in low grade fibromyxoid sarcoma.

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Reference: Superficial acral fibromyxoma
Board review style question #2
Superficial acral fibromyxoma Superficial acral fibromyxoma


A 30 year old woman presented with a slow growing painless subungual mass. Plain Xray revealed erosion of underlying bone. Magnetic resonance imaging (MRI) confirmed a soft tissue lesion and bone erosion. Excision specimen revealed histological features as shown in the given H&E image. The provided IHC stain is CD34. What is the treatment of choice?

  1. Local excision
  2. Moh's microsurgery
  3. Neoadjuvant chemotherapy
  4. Radiation
  5. Wide excision
Board review style answer #2
A. Local excision. The current diagnosis of superficial acral fibromyxoma warrants only local excision with adequate margins. Answer B is incorrect because Moh's microsurgery is a procedure done for skin cancers, including basal cell carcinoma, squamous cell carcinoma and melanoma at critical sites like eyes, ear, nose and lips where excision margins are sent for frozen section to secure clear margins with minimal tissue defect. Answers C, D and E are incorrect because a benign diagnosis does not merit chemotherapy, radiation or wide excision.

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Reference: Superficial acral fibromyxoma
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