Onychomatricoma

What is onychomatricoma?

Onychomatricoma is a rare, benign fibroepithelial tumour of the nail matrix [1].

 

Who gets onychomatricoma?

Onychomatricoma typically affects Caucasian women, with a peak incidence in the fifth decade of life. It is rarely observed in children [2].

What causes onychomatricoma?

The exact pathophysiology of onychomatricoma is unknown, although it could be precipitated by trauma [3,4].

What are the clinical features of onychomatricoma?

Onychomatricoma more commonly affects the fingers than the toes. It could involve either a single digit or multiple digits simultaneously [2,5].

Onychomatricoma is typically slow-growing and painless. Its classic clinical features include [1,4,5]:

• A yellowish and thickened nail plate
• Proximal splinter haemorrhage
• Longitudinal overcurvature of the nail plate
• Finger-like projections penetrating the nail plate, resulting in the characteristic 'woodworm' cavities when viewed from the nail plate’s free margin.

Rarer presentations of onychomatricoma include longitudinal melanonychia, [subungual haematoma]([sitetree_link,id=Loading, please wait...]>), and dorsal pterygium [4,6].

Dermoscopic features of onychomatricoma include perforations in the distal portion of the nail plate, haemorrhagic striae, as well as white longitudinal grooves corresponding to the nail plate channels [5].

What are the complications of onychomatricoma?

Onychomatricoma may be complicated by onychomycosis, so both conditions can coexist [1,5]. Delayed diagnosis and treatment are not uncommon due to unfamiliarity with onychomatricoma [2].

How is onychomatricoma diagnosed?

Onychomatricoma is diagnosed based on its characteristic clinical features supplemented by dermoscopy, imaging, and histopathology [6].

Imaging may be considered to guide clinical decisions before excision if the presentation is non-specific or unclear [4]. Imaging modalities that could help with diagnosing onychomatricoma include [5,7]:

• Ultrasound — this may show hypoechogenic tumour affecting the nail matrix and hyperechogenic area corresponding to the finger-like projections; reduced blood flow could also be observed
• MRI — the affected nail matrix typically shows a low signal uptake, while the finger-like projections have high uptake.

Histopathological evaluation could be performed on either nail clippings or a resected tumour, which is considered the gold standard [1,4–7]:

• Nail clippings — these classically show a thickened nail plate with cavities filled with serous material, lined by a thin layer of epithelium at the periphery
• A resected tumour — distinctive histological features confirm the diagnosis.
  • The proximal nail folds — ungual protrusions and deep epithelial invaginations
  • The distal zone (corresponding to the lunula) — fibroepithelial projections perforating the nail plate, originating from the matrix.

Immunohistochemistry although helpful, is not routinely required in typical cases [5].

What is the differential diagnosis for onychomatricoma?

Common differential diagnoses of onychomatricoma include:

• Fibrokeratoma (a rare neoplasm)
• Periungual fibroma
• Onychomycosis
• Squamous cell carcinoma
• Intraepidermal squamous cell carcinoma
• Subungual viral wart.

What is the treatment for onychomatricoma?

The definitive treatment for onychomatricoma is complete surgical excision [5].

What is the outcome for onychomatricoma?

Onychomatricoma typically resolves without local recurrence with complete surgical excision [2,4].