Sociedade Brasileira de Dermatolodia Surgical & Cosmetic Dermatology


ISSN-e 1984-8773

Volume 5 Number 1

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Continuing medical education



Nilton Di Chiacchio1, Glaysson Tassara Tavares1, Emerson Henrique Padoveze1, Diego Leonardo Bet1, Nilton Gioia Di Chiacchio1

PhD in Dermatology, Head of the Dermatology Department of the Hospital do Servidor Público Municipal de São Paulo—São Paulo (SP), Brazil1, Volunteer Physician at the Dermatology Medical Residency of the Hospital Central da Universidade Federal de Minas Gerais (UFMG)—Belo Horizonte (MG), Brazil2, Assistant Physician at the Dermatology Clinic of the Hospital do Servidor Público Municipal de São Paulo3, Volunteer Assistant Physician at the Dermatology Clinic of the Hospital do Servidor Público Municipal de São Paulo4, Intern Physician at the Micrographic Surgery Service of the Dermatology Clinic of the Hospital do Servidor Público Municipal de São Paulo5

Received on: 27 February 2013 Approved on: 15 March 2013 The present study was carried out at the Hospital do Servidor Público Municipal de São Paulo—São Paulo (SP), Brazil. Financial support: None Conflict of interest: None



Onychomatricoma is a benign neoplasia that occurs pecifically in the nail apparatus. It was described in 1992, and is the only tumor in which the change of the nail plate is actively caused by the lesion. It lies in the nail matrix,and has fingerlike projections that are embedded in the nail plate, resulting in thickening, longitudinal grooves, yellow discoloration and splinter hemorrhages. Although described as a rare tumor, it is believed to be underdiagnosed. The present study is aimed at reviewing onychomatricoma’s clinical features as well as the complementary examinations that are used to recognize and diagnose this tumor.



Onychomatricoma (OM) is a benign tumor arising from the nail matrix. It was first described by Baran and Kint in 1992 1 as the first onychomatrixoma. In 1995, Hanekee and Fränken, based on histological aspects, proposed the term onychomatricoma, which has been used since then. 2 Also, on a histological basis, other quotes and nomenclature, such as onychoblastoma, onychoblastic fibroma and atypical onychoblastic fibroma are currently found, however the term onychomatricoma remains the most frequently used and cited in the current literature. 3, 4

It is considered a rare and specific tumor of the nail apparatus, characterized by the presentation of fingerlike projections from the matrix, and is the only tumor in which alterations of the nail plate are actively produced by the lesion. 2,5

Since its first description, just over 40 cases have been reported. Although considered a rare condition, its clinical, radiological, dermoscopic, histological, and electron microscopy-based aspects have been well documented. Recent studies consider the tumor''''''''s genetic alterations, such as losses on chromosome 11. 4 Its slow growth and the absence of pain in most cases explain patients'''''''' typical delay in seeking medical attention.


Although onychomatricoma''''''''s etiology is still not fully understood, trauma is considered the main predisposing factor. Another hypothesis is that it corresponds to a reactive picture and not to a matrix tumor. 2 Some authors suggest that onychomatricoma is an epithelial and conjunctive tissue hamartoma that mimics the nail matrix''''''''s structures. 1,6,7


Onychomatricoma affects mainly females (2,16:1), with the peak of incidence around the age of 51. 8 It rarely affects children, with only one case described in the literature. 9 Despite its prevalence in Caucasians, there are reports of involvement of other ethnicities 10 and one case described in a patient of African heritage. 11 It rarely causes pain and fingers are more affected than toes— this information is biased however, since there is greater patient concern and demand for a doctor''''''''s intervention for lesions that affect fingers. 4

Onychomatricoma classically manifests with the clinical tetrad: (1) yellowish longitudinal band of variable thickness, (2) splinter hemorrhages preferentially affecting the proximal portion of the nail plate, (3) longitudinal and transverse hypercurvature of the nail plate, and (4) fingerlike projections that emerge from the nail matrix, leaving cavities in the nail plate. 12 (Figure 1)

Due to the fact that it is a matrix tumor, a nodule can be clinically observed in the proximal nail fold. Besides the clinical tetrad, onychomatricoma can present as longitudinal melanonychia (hypermelanosis), nail dystrophy, subungual hematoma, verrucous aspect in the proximal nail fold, dorsal pterygium, giant variant and normal type of pseudo-fibrokeratoma, in addition to the resemblance to 11 onychomycosis. 13,14 (Figure 2) The main differential diagnoses include subungual exostosis, fibrokeratoma, fibroma, onychomycosis, epidermoid carcinoma, Bowen''''''''s disease, keratoacanthoma, verruca vulgaris, acral superficial fibromyxoma, melanoma, bacterial infections, dermatofibrosarcoma protuberans, porocarcinoma, andosteochondroma. 4

Onychomycosis has been implicated as a predisposing factor for the emergence of onychomatricoma (reactive theory of the lesion). On the other hand, onychomatricoma can also be considered a predisposing factor for onychomycosis 9,15


In addition to the classic tetrad of signs, other methods such as dermoscopy of the nail plate,16 ultrasound17,18 MRI19 ungual clipping, 20 and histologic study, 7,13,21 can be employed to aid in the diagnosis of onychomatricoma. (Figures 1 and 2)

The dermoscopy of the nail plate evidences perforations in the distal portion of the ungual plate,16 hemorrhagic striae, and white longitudinal grooves corresponding to the nail plate channels. 5 (Figure 31)

Radiologically, there is no bone involvement linked to onychomatricoma. 20

Ultrasound has been shown useful in the tumor''''''''s detection, delimitation, and topography. For a good view of the lesion at this body site, the device''''''''s frequency should be set at seven to 15 MHz. The tumor is seen as a hypoechogenic area affecting the nail matrix and a hyperechogenic area corresponding to the fingerlike projections, in addition to having a low blood flow. 18

With MRI, the tumor is easily seen in the sagittal cuts, affecting the nail matrix, with low signal capture, and resembling normal epidermis. At the distal section, the digitations are observed with high signal capture, as the mucoid stroma present in the area of the tumor has a high concentration of water (T2). The axial cuts allow the viewing of perforations in the nail plate. 19 Nail clipping is the histologic study of the nail plate in which the analyzed specimen is removed by cutting the distal part of the nail plate. This technique allows the visualization of the gaps (perforations) of different shapes and sizes, suggestive of onychomatricoma. The technique is deemed straightforward, fast, cost effective, and minimally invasive. In addition to allowing the diagnosis of the tumor, it provides assistance in the differential diagnosis of onychomicosis using PAS staining, and enables the immunohistochemical study of the nail plate. 21

Diagnosis is confirmed histologically. It is a fibroepithelial tumor composed of two distinct areas: the proximal and distal zones. The first is located below the posterior nail fold and is characterized by deep epithelial invaginations filled by a thick keratin zone in the shape of a "V", well-defined fibrillar and fibrotic stroma, in addition to the thickening of the nail plate without cavities. The distal zone, which corresponds to the lunula region, is characterized by fingerlike projections, perforations in the nail plate, and deep and poorly delimited penetration of the connective stroma in the dermis. 4,7

The fingerlike projections are formed by matrix epithelium, located around the connective tissue, in the antero-oblique axis, that proliferate and cause perforations in the nail plate, generating cavities, which in the distal part of the lunula lose their epithelium and are filled with serous fluid. 4,7

Some authors mention the presence of mast cells in the stroma of onychomatricomas. 22 The keratinization zone can be adhered to the nail plate. Thus, both the tumor and the removed plate must be sent for histological examination. 4 The splinter hemorrhages seen in the nail plate''''''''s proximal region, correspond to the fingerlike projections'''''''' loose vascular stroma. 12

The yellowish color occurs due to the thickening of the nail plate, resulting from the layers of keratinization that involve the fingerlike projections.. Its intensity is proportional to the degree of thickening. 12

The main histological differential diagnoses are the fibrokeratoma and the ungual fibroma. In the longitudinal cuts of the onychomatricoma, the structure is reminiscent of a fibrokeratoma; nevertheless that diagnosis may be excluded due to the presence of multiple fingerlike projections, the absence of a cutaneous horn, and the presence of cavities filled with serous fluid in the distal portion of the nail plate. The onychomatricoma''''''''s stroma, located in the lunula, may suggest the diagnosis of fibroma, which in turn may be discarded by the hyperplasic and onychogenic nature of the epithelium. Moreover, ungual fibroma generates a longitudinal depression in the nail plate, in the shape of a channel, due to the compression in the nail matrix. 12

The immunohistochemical study using the cell proliferation marker Ki67 (MIB-1) demonstrates a low rate of cell proliferation in the onychomatricoma. 2 The observed expression pattern of the cytokeratin and integrins is identical to those of the normal matricial epithelium, in spite of the fact that the antibody AE13—specific for the trichocystic keratin Ha 1-4 —can be potentially useful as an onychomatricoma marker. 23

A study with adhesion proteins demonstrated the absence of beta-catenin in comparison with other ungual tumors. 24 The involucrin is expressed from the basal layer up to the upper part of the epithelium, where it is more pronounced and the transglutaminase-1 is limited. 5The immunophenotyping expresses CD34, but not CD99 or epithelial membrane antigen, S100 protein, actin, and desmin. 5

In electron microscopy, the basal cells apparently contain a reduced number of tonofilaments and desmosomes, which have a non-uniform development. 8


The treatment for onychomatricoma is surgical (Figure 4). After anesthesia (proximal or distal locking) the proximal nail fold is bent and the nail plate is gently removed in order to prevent the villi from being torn. The tumor must be removed completely. Nail dystrophy after surgical removal can occur depending on the preservation of the nail matrix during the removal of the tumor. 25


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