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Onychomatricoma: A Rare Tumor of Nail Matrix

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Hong Jin Joo
Hong Jin Joo
Hong Jin Joo
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Mi Ri at United Arab Emirates University
Mi Ri
Baik Kee Cho at Catholic University of Korea
Baik Kee Cho
Gyeol Yoo
Gyeol Yoo
Gyeol Yoo
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Abstract and Figures

Onychomatricoma is a rare tumor of the nail matrix. Until now, few cases of onychomatricoma have been reported in the literature. Immunohistochemically, CD10, a marker of the onychodermis, is expressed in the stroma of the onychomatricoma. In the present case, a 27-year-old woman presented with an 8-year history of a yellowish, thickened, and overcurved nail plate of the right index finger, mimicking onychomycosis. She had been treated for 4 years with antifungal agents by general physicians, without improvement. The nail was surgically removed, and the tumor at the nail matrix was excised. The nail plate continued to grow in the 2 months after the excision. This is a case of onychomatricoma in South Korea, which was initially misdiagnosed as onychomycosis. In addition, we present a review of the literature regarding clinical, sonographic, and histological features, differential diagnoses, and treatment of onychomatricoma.
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Onychomatricoma: A Rare Tumor of Nail Matrix
Vol. 28, No. 2, 2016
237
Received August 5, 2015, Revised December 16, 2015, Accepted for
publication December 24, 2015
Corresponding author: Hyun Jeong Park, Department of Dermatology,
Yeouido St. Mary’s Hospital, College of Medicine, The Catholic University
of Korea, 10 63-ro, Yeongdeungpo-gu, Seoul 07345, Korea. Tel:
82-2-3779-1391, Fax: 82-2-783-7604, E-mail: hjpark@catholic.ac.kr
T
his is an Open Access article distributed under the terms of the Creative
Commons Attribution Non-Commercial License (http://creativecommons.
org/licenses/by-nc/4.0) which permits unrestricted non-commercial use,
distribution, and reproduction in any medium, provided the original work
is properly cited.
Copyright © The Korean Dermatological Association and The Korean
Society for Investigative Dermatology
pISSN 1013-9087ㆍeISSN 2005-3894
Ann Dermatol Vol. 28, No. 2, 2016 http://dx.doi.org/10.5021/ad.2016.28.2.237
CASE REPORT
Onychomatricoma: A Rare Tumor of Nail Matrix
Hong Jin Joo, Mi Ri Kim, Baik Kee Cho, Gyeol Yoo
1
, Hyun Jeong Park
Department of Dermatology, College of Medicine, The Catholic University of Korea,
1
Department of Plastic and Reconstructive Surgery,
Yeouido St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea
Onychomatricoma is a rare tumor of the nail matrix. Until
now, few cases of onychomatricoma have been reported in
the literature. Immunohistochemically, CD10, a marker of
the onychodermis, is expressed in the stroma of the ony-
chomatricoma. In the present case, a 27-year-old woman
presented with an 8-year history of a yellowish, thickened,
and overcurved nail plate of the right index finger, mimicking
onychomycosis. She had been treated for 4 years with anti-
fungal agents by general physicians, without improvement.
The nail was surgically removed, and the tumor at the nail
matrix was excised. The nail plate continued to grow in the
2 months after the excision. This is a case of onychoma-
tricoma in South Korea, which was initially misdiagnosed as
onychomycosis. In addition, we present a review of the liter-
ature regarding clinical, sonographic, and histological fea-
tures, differential diagnoses, and treatment of onychoma-
tricoma. (Ann Dermatol 28(2) 237∼241, 2016)
-Keywords-
Onychomatricoma, Onychomycosis
INTRODUCTION
Onychomatricoma, which was first described in 1992 by
Baran and Kint
1
, is a rare benign tumor of nail matrix
origin. Since its description, no more than 80 cases have
been reported in the literature
1–7
. The four main clinical
features of onychomatricoma include thickening of the
nail plate, transverse or longitudinal overcurvature, xan-
thonychia, and multiple splinter hemorrhage. After avul-
sion of the nail plate, onychomatricoma presents as a vil-
lous matrix tumor with projections that penetrate the
thickened nail plate. Diagnosis is based on clinical, sono-
graphic, and histopathological findings. The treatment for
onychomatricoma is surgical, and the tumor must be re-
moved completely. This is the second case of onychoma-
tricoma in South Korea, which was initially misdiagnosed
as onychomycosis in this patient. This is also the first re-
ported case for which immunohistochemical staining of
an onychomatricoma tissue sample was performed
8
.
In this report, we present clinical, histological, immuno-
histochemical, and sonographic findings of onychoma-
tricoma in a 27-year-old Korean woman.
CASE REPORT
A 27-year-old woman presented with an 8-year history of
gradual nail dystrophy on the right index finger, which
was initially misdiagnosed as onychomycosis; she had
been treated for 4 years with antifungal agents by general
physicians without improvement. On physical examina-
tion, the nail plate of the right index finger was thickened
and dark yellowish in color, mimicking onychomycosis. It
exhibited scattered splinter hemorrhages and overcur-
vature in the longitudinal plane (Fig. 1). She had neither a
history of trauma to the nail nor a personal or family his-
tory of skin cancer or dermatological disorders. A fungal
culture of the nail plate yielded negative results, and ra-
diography of the affected finger revealed no bone involve-
ment linked to onychomatricoma. Ultrasonography re-
vealed a hypoechogenic tumoral lesion in the nail matrix
HJ Joo, et al
238 Ann Dermatol
Fig. 1. (A) Yellowish, thickened
nail plate of the right index finger,
with splinter hemorrhages and
longitudinal bands mimicking ony-
chomycosis. (B) Lateral view of the
nail plate showing longitudinal
overcurvature.
Fig. 2. Ultrasonographic image showing a 2×5×7 mm hypoechogenic tumor under the proximal nail fold (A, B) and hyperechogenic
villous projections of the nail matrix having low blood flow (C). (A) Transversal view. (B, C) Longitudinal view.
Fig. 3. (A) Intraoperative view of the filamentous tumor arising from the nail matrix. (B) Macroscopic appearance of the removed
tumor with finger-like projections. (C) Proximal portion of the nail plate showing multiple cavities characteristic of onychomatricoma.
(D) Normal nail plate growth 2 months after the excision.
and a hyperechogenic area corresponding to fingerlike
projections with low blood flow (Fig. 2). The nail was sur-
gically removed, and the tumor at the nail matrix was
excised. When the nail plate was initially avulsed, a firmly
attached, filamentous tumor was observed arising from the
nail matrix (Fig. 3A). The excision specimen was a flesh-col-
ored tumor with fingerlike projections emerging from the
nail matrix, leaving cavities in the nail plate (Fig. 3B). The
proximal portion of the nail plate contained multiple cav-
ities, which is characteristic of onychomatricoma (Fig. 3C).
Onychomatricoma: A Rare Tumor of Nail Matrix
Vol. 28, No. 2, 2016
239
Fig. 4. (A, B) Histopathological section showing characteristic filiform projections lined by epithelium emerging from the nail matrix.
(A) Medium-power view (H&E, ×100). (B) High-power view (H&E, ×400). (C) Immunohistochemical stain showing CD10 diffusely
expressed in the stroma of the section. (D) Immunohistochemical stain showing CD34 diffusely expressed in the stroma of the section.
(C, D) Medium-power view (×100).
The normal nail plate continued to grow in 2 months after
the excision (Fig. 3D). The excised tumor consisted of a
connective tissue core and characteristic filiform projec-
tions lined by epithelium from the nail matrix lacking
granular and horny layers (Fig. 4A, B). Immunohistochemical
examination revealed that CD10 and CD34 were diffusely
expressed in the stroma of the onychomatricoma (Fig. 4C,
D). Periodic acid-Schiff histochemical stain was negative
for fungal organisms.
DISCUSSION
Onychomatricoma, which is a benign tumor of nail matrix
origin, has been rarely reported
1-7
. This may be partly due
to the anatomic particularities of the nail apparatus and
the often fragmented tissue specimens submitted to path-
ologists
4
. We report the clinical, radiological, sonographic,
and histological features and treatment of a case of ony-
chomatricoma, including a review of relevant literature.
Recent studies have reported that onychomatricoma main-
ly affects middle-aged women, with peak incidence at
around the fifth decade of life
2,3
, although few case reports
indicate that the onychomatricoma development has no
sex predilection
6
. Onychomatricoma predominantly af-
fects the fingers, with either single or multiple digits af-
fected simultaneously
1
. Onychomatricoma may be com-
plicated by fungal infection, and the tumor is often mis-
diagnosed as onychomycosis and treated as such
9,10
. In re-
cent studies, patients with onychomatricoma considered
to have genetic alterations, such as loss of chromosome
11
.
The classic tetrad signs include yellowish, thickened nail
plate, splinter hemorrhage, transverse overcurvature of the
nail plate, and woodworm-like cavities in the distal mar-
gin of the nail plate. After avulsion of the nail plate, the
HJ Joo, et al
240 Ann Dermatol
presence of digitiform projections is quite suggestive of
the diagnosis. A villous matrix tumor with projections pen-
etrates the thickened nail plate.
Diagnosis is based not only on the classic tetrad signs but
also on additional diagnostic methods, such as dermo-
scopy, ultrasonography, and histopathological findings.
Dermoscopy shows perforations in the distal portion of
the nail plate, hemorrhagic striae, and white longitudinal
grooves corresponding to the nail plate channels
12
.
Radiological examination shows no underlying bone in-
volvement linked to onychomatricoma
13
. Ultrasonographic
examination shows a hypoechoic tumoral lesion affecting
the nail matrix and a hyperechogenic area corresponding
to the fingerlike projections, in addition to having low
blood flow
14
.
Onychomatricoma has distinctive histological features that
confirm the diagnosis. Onychomatricoma is a fibroepithelial
tumor comprising two distinct areas
15
. The proximal zone
is located below the posterior nail fold and is charac-
terized by deep epithelial invaginations occupied by over-
lying ungual protrusions. The distal zone, which corre-
sponds to the lunula, comprises epithelial digitations origi-
nating from the matrix epithelium, which proliferate and
cause perforations in the nail plate. Recently, Lee
8
sug-
gested that onychomatricoma might derive from the ony-
chodermis because CD10, a marker of the onychodermis,
is expressed in the stroma of onychomatricoma. Consistent
with this finding, CD10 was diffusely expressed in the
stroma of the onychomatricoma in our case. In addition,
CD34, which is expressed in dendritic or fibroblast-like
mesenchymal cells that are ubiquitously distributed in the
dermis
16
, was diffusely expressed in the stroma of the
onychomatricoma.
Misciali et al.
17
reported onychoblastoma as a variant of
onychomatricoma. Clinical examination showed a thick-
ened nail plate with multiple cavities and a digitated tu-
mor originating from the nail matrix, which is similar to
that found for onychomatricoma. The tumor was dis-
tinguished from onychomatricoma by a unique arrange-
ment with follicular differentiation and expression of cyto-
keratin (CK)5⁄6 and CK14 by keratin immunohistochemistry.
However, Baran
18
suggested that there was lack of evi-
dence for differentiating onychoblastoma from onychoma-
tricoma, and the gross morphology of this tumor and the
channels within the nail plate were all consistent with
onychomatricoma.
Differential diagnoses include fibrokeratoma, periungual
fibroma, onychomycosis, squamous cell carcinoma, Bowen’s
disease, subungual verruca vulgaris, longitudinal melano-
nychia, and osteochondroma
2
. Among these, fibroker-
atoma and periungual fibroma are the main histological
differential diagnoses. In the longitudinal sections of the
onychomatricoma, the histopathological features are remi-
niscent of those of fibrokeratoma. However, that diagnosis
may be excluded because fibrokeratoma lacks the multi-
ple fibroepithelial projections and nail plate perforations
characteristic of onychomatricomas
19
. Moreover, although
ungual fibroma also produces longitudinal grooving of the
nail plate due to the compression in the nail matrix, the
differential diagnosis of onychomatricoma is possible be-
cause of the lack of hyperplastic onychomatricial epi-
thelium
7
.
The treatment for onychomatricoma is surgical excision
20
.
After anesthesia, the nail plate is removed, permitting visu-
alization of the matrix tumor projections. The tumor must
be completely excised, including the normal nail matrix
proximal to the lesion, in order to prevent local re-
currence
5
. Only one local recurrence has been reported
within a mean follow-up time of 20.1 months
4
. With the
exception of this case, most previous cases had no local
recurrence
2
. Nail dystrophy can occur depending on the
preservation of the nail matrix during tumor excision
2
.
The diagnosis of onychomatricoma is often delayed.
Patients’ typical delay in seeking medical attention may be
attributed to the slow growth and absence of pain in most
cases
3
. In addition, many cases are misdiagnosed as ony-
chomycosis
20
, like our case, probably because dermatolo-
gists are not familiar with its clinical features. Therefore,
we are reporting a typical case of onychomatricoma to
help dermatologists recognize the clinical features of ony-
chomatricoma and detect this uncommon nail matrix tu-
mor early.
ACKNOWLEDGMENT
This work was supported by the Basic Science Research
program through the National Research Foundation of
Korea (NRF), which is funded by the Ministry of Education,
Science and Technology (2015R1C1A2A01055073).
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... Histologically, OCM shows acanthotic, papillomatous, or keratogenous features with minimal melanocyte changes [4,5]. Of the reported cases, OCM has been found in 11 males [1,2,[4][5][6][7][8], 7 females [1,6,[8][9][10][11], with 1 case in late childhood [11]. Additionally, there were recent findings in one South Korean female, one Chinese male, one Taiwanese male, and one Taiwanese female [7][8][9]. ...
... Of the reported cases, OCM has been found in 11 males [1,2,[4][5][6][7][8], 7 females [1,6,[8][9][10][11], with 1 case in late childhood [11]. Additionally, there were recent findings in one South Korean female, one Chinese male, one Taiwanese male, and one Taiwanese female [7][8][9]. There are no reported cases of OCM in Black individuals as well as no reported cases found in toenails. ...
... This is the first case to our knowledge of OCM reported in a Black patient. Differentiating features between OCM and other possible diagnoses include longitudinal erythromelanonychia for subungal seborrheic keratosis; verrucous band of thickened nail plate with a yellowish discoloration in onychocytic carcinoma; and xanthonychia with splinter hemorrhages mimicking onychomycosis seen in onychomatricoma [4,9,12,13]. Differential diagnosis for longitudinal melanonychia may also include melanoma and pigmented Bowen's disease [14]. ...
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Introduction: Onychocytic matricoma (OCM) is a benign acanthoma of the nail matrix that presents with longitudinal melanonychia and nail thickening. Only 18 previously reported cases of OCM are in the literature since it was first described in 2012. Case presentation: The purpose of this case report was to report a unique presentation of OCM in the toenail of a Black patient as well as to review the clinical presentation, histologic features, and management of this rare entity. Previously described cases presented on the fingernails and were predominantly in white males. Conclusion: OCM is a benign entity that may mimic a nail unit melanoma or squamous cell carcinoma especially when pachyonychia is present. Despite some clinical clues to suggest a diagnosis of OCM, a nail matrix biopsy is often required to rule out malignancy.
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... 3.11.7 Onychomatricoma -Definition: Onychomatricoma is a benign fibroepithelial neoplasm of the nail matrix that penetrates the nail plate (Cañueto et al. 2011). It commonly affects women especially in the fifth decade and predominantly involves fingers, singly or multiply at a time (Joo et al. 2016;Tavares et al. 2015). The etiology of this disease is not fully known, but onychomycosis and genetic alterations in chromosome 11 have been reported as predisposing factors (Cañueto et al. 2011). ...
... -Prognosis and treatment: Surgical excision is the primary treatment. Upon nail plate avulsion, the tumor is completely cleared away, and normal nail matrix proximal to affected area is removed in order to prevent recurrence (Joo et al. 2016). Although nail dystrophy occurs in some cases, overall outcomes for this treatment approach are positive nail (Joo et al. 2016;Tavares et al. 2015). ...
... Upon nail plate avulsion, the tumor is completely cleared away, and normal nail matrix proximal to affected area is removed in order to prevent recurrence (Joo et al. 2016). Although nail dystrophy occurs in some cases, overall outcomes for this treatment approach are positive nail (Joo et al. 2016;Tavares et al. 2015). -Differential diagnosis: Fibrokeratoma, periungual fibroma, onychomycosis, Bowen's disease, longitudinal melanonychia, subungual verruca vulgaris, and SCC (Joo et al. 2016;Cañueto et al. 2011). ...
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... 7 Intraoperatively, a filamentous tumor with digitiform projections that penetrate the nail plate leading to woodworm-like cavities is usually found. 10,11 Histopathological evaluation characteristically exhibits a fibroepithelial tumor composed of a proximal pedunculated base and a distal zone with multiple epithelial digitations. 2,3 A biphasic fibrous stroma, superficially cellular and deeply collagenized and relatively hypocellular, is present throughout the tumor. ...
... 2,3 The treatment of choice for onychomatricoma is complete surgical excision and is typically curative. 10 Secondary ungual dystrophy and recurrences have been rarely reported. 5,10 Conclusion Onychomatricoma should be kept in mind in the differential diagnosis of nail apparatus changes to avoid misdiagnosis and proper treatment delay. ...
... 10 Secondary ungual dystrophy and recurrences have been rarely reported. 5,10 Conclusion Onychomatricoma should be kept in mind in the differential diagnosis of nail apparatus changes to avoid misdiagnosis and proper treatment delay. The current case illustrates the Indian Journal of Dermatology, Venereology and Leprology | Volume XX | Issue XX | Month 2021 importance of suspecting an underlying onychomatricoma toward a single long-standing distorted nail unresponsive to fungicidal treatment. ...
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... Onychomatricoma is a rare benign subungual tumour affecting the germinal nail matrix, first reported by Baran and Kint in 1992. 1 The tumour classically presents with a tetrad of: yellow discolouration with thickening of the nail plate, splinter haemorrhage, transverse nail plate overcurvature, and worm-like cavitation of the nail plate. 2 The presence of frond-like cavitations in the nail plate is further suggestive of onychomatricoma. 2 Differentials for onychomatricoma include Bowen's disease, fibrokeratoma, onychomycosis, squamous cell carcinoma, and subungual verruca vulgaris amongst others. 3 Nevertheless, onychomatricoma appears to be the only one that actively produces nail plate substance, lending to its thickening. ...
... Onychomatricoma is a rare benign subungual tumour affecting the germinal nail matrix, first reported by Baran and Kint in 1992. 1 The tumour classically presents with a tetrad of: yellow discolouration with thickening of the nail plate, splinter haemorrhage, transverse nail plate overcurvature, and worm-like cavitation of the nail plate. 2 The presence of frond-like cavitations in the nail plate is further suggestive of onychomatricoma. 2 Differentials for onychomatricoma include Bowen's disease, fibrokeratoma, onychomycosis, squamous cell carcinoma, and subungual verruca vulgaris amongst others. 3 Nevertheless, onychomatricoma appears to be the only one that actively produces nail plate substance, lending to its thickening. ...
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... An onychomatricoma is a benign tumor of the nail matrix that may present with splinter hemorrhages, xanthonychia, nail plate thickening, and cavities at the free edge of the nail plate [16]. It is histologically characterized by fibroepithelial projections surmounted by benign epithelium, creating perforations that form channels in the nail plate [17]. Periungual Bowen's disease is an in situ SCC of the nail [18]. ...
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... Both our cases demonstrated different clinical phenotypes. In patient 1 (as mentioned in Table 1 and Fig. 1), diagnostic possibilities considered included pyogenic granuloma, superficial acral fibromyxoma, onychomatricoma, and subungual SCC [8,9]. Clinical and microscopic features availed for evaluating this patient have been lucidly elaborated in Table 2. ...
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Pincer nail is a deformity characterized by excessive transverse curvature of nail, progressively increasing along its longitudinal axis. The curvature is greatest at the distal end, leading to an ingrown nail, producing pain, discomfort, and significant cosmetic alteration. It is a severe variant of ingrown nail, often attributed to causes such as anatomical variation of nail plate axis, tight footwear, gait abnormalities, and so on. Correspondingly, its management involves the removal of the lateral ingrowing nail plate or the lateral hypertrophic nail folds. We report a young male who presented with symptomatic pincer nail deformity. However, on exploration there was a midline onychomatricoma, leading to the thickening of the central part of the nail plate, causing incurving of the lateral nail plate and discomfort. The report serves to highlight the need for a comprehensive evaluation of pincer nails, to assess for matrix disease as well, because the surgical approach will differ accordingly.
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Onychomatricoma: A tumor unknown to dermatologists
Article
Full-text available
  • Mar 2015
A sixty-one year old white female was referred to the Dermatology Department to treat an ingrown nail in the inner corner of the left hallux. Examination of the entire nail unit showed the presence of xanthonychia in the outer corner besides thickening and increase in the transverse curvature of the nail plate. Dermoscopy and nuclear magnetic resonance of the free edge of the nail plate detected characteristic signs of onychomatricoma, a diagnosis that was later confirmed by anatomopathological exam.
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Onychomatricoma: Epidemiological and clinical findings in a large series of 30 cases
Article
  • May 2015
  • BRIT J DERMATOL
Onychomatricoma (OM), first described by Baran and Kint(1) , is considered a rare benign tumor of the nail matrix with no more than 80 cases reported in the literature. Fingernails of adult white patients are most commonly affected. Reported clinical features include localized or diffuse thickening of the nail plate, transverse over curvature, xanthonychia, multiple splinter hemorrhages, which often affect the proximal nail plate, and presence of holes in the distal margin of the nail plate (2) . This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
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Onychoblastoma - Hamartoma of the Nail Unit: A New Entity?
Article
  • Jun 2008
  • J CUTAN PATHOL
A 50-year-old Peruvian man presented with a 4–5 years history of a 1,2 × 0,7 cm subungual verrucous mass that extended from the proximal nail fold to the hyponychium of the 2nd left toe. Histology of the nail bed showed a nodular tumour with multiple structures, similar to the infundibulum of the follicles, and germ like aggregations often joined to a follicular papilla. Few scattered neoplastic cells were necrotic. The stroma surrounding the nodular aggregations was made up of delicate fibrillary bundles of collagen associated with numerous oval fibrocytes. The histological findings remind us a neoplasm with follicular differentiation: trichoblastoma. A tumor with these histological aspects on the nail unit has never been reported. We name this benign neoplasm, which probably represents an hamartoma, onychoblastoma. Differential diagnosis of this case includes basal cell carcinoma (BCC) of the nail unit which is rare and mostly localised in the nail folds. The main histopathologic findings of nodular BCC are asymmetry, ulceration and its poorly circumscription. The hair follicle and the nail share similar embryological and anatomical features and the occurrence of a tumor with follicular differentiation in the nail further demonstrates the common origin of these adnexal structures.
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Onychomatricoma
Article
  • Jan 2011
  • ANN DERMATOL VENER
We report a case of onychomatricoma, which is a rare benign tumour originating in the germinal matrix of the nail. The diagnosis can be made on the typical clinical findings and confirmed by histology. Complete excision is the treatment of choice.
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Onychomatricoma: Genome-wide analyses of a rare nail matrix tumor
Article
  • Mar 2011
Onychomatricoma (OM) is a rare benign tumor of the nail matrix in which genome-wide analyses have never been performed. It is clinically characterized by an increased transversal curvature of the nail plate, a longitudinal yellowish discoloration, and splinter hemorrhages. Once the nail plate has been removed, fingerlike fibrokeratogenous projections appear through the proximal nailfold. Histologically, it is a fibroepithelial tumor with well-established features. In this article, a comprehensive review of this tumor is made. We performed a genome-wide analysis of an OM, in an attempt to shed light on the mechanisms underlying its development. We report a 36-year-old man who was given a diagnosis of OM involving his fourth right toenail. To investigate molecular genetic alterations, we carried out two approaches, fluorescent in situ hybridization and array-based comparative genomic hybridization, in our patient. Genomic testing of OM showed 34 genomic alterations, with most of the genomic losses being on chromosome 11. Array-based comparative genomic hybridization showed the deletion of 11p15.4, which harbors STIM-1, 11q14.2 (RP-11 292E14), which harbors the Cathepsin C gene, 11q14 (RP11-281F10-RP11-265F24), and 11q21 (RP11-203F8 and RP11 183A22). This work is an initial approach to a genome-wide study of this tumor. Further studies (with more cases) must be conducted to pinpoint possible candidate genes for the development of OM. Array-based comparative genomic hybridization showed important genomic alterations in OM, especially genomic losses. Most genomic losses affected the chromosome 11 in our patient. The STIM-1 and the Cathepsin C genes might play a role in the development of OM.
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Onychomatricoma: New Clinical and Histological Features. A Review of 19 Tumors
Article
  • Feb 2010
To further define the clinicopathological spectrum of onychomatricoma (OM). We report the clinical feature, histological, and immunophenotypic characteristics of 19 cases of OM diagnosed between 2002 and 2007. The characteristic histologic appearance of OM is sometimes difficult to grasp because of 3 main factors: the anatomic particularities of the nail apparatus, the often fragmented aspect of the tissue specimen, and the choice of the section planes, which strongly modified the morphologic appearances observed. To prevent these difficulties, we built a tridimensional model using serial, transverse, and longitudinal sections. This reconstitution gives us a better understanding of the apparent diversity of the morphologic aspects observed in linking them to the anatomic site of the tumor. OM of the matrix is characterized by a thick nail plate with porch roof. OM of the ventral aspect of the proximal nail fold (PNF) is characterized by a nail plate without porch roof, exhibiting either a woodworm-like appearance or multiple cavities. In this second category, the fibrous base becomes elongated in shape, taking the shape of the anatomic contour of the PNF. The stroma gives rise to numerous fibroepithelial digitations. This pattern is different from the classical OM visualized in longitudinal sections, which appears as a single and large fibroepithelial tumor, that is, the multiple distal epithelial digitations arranged along a transversal plane are not seen. In the PNF variant, the characteristic clinical signs of OM fail to appear. We individualize 3 misleading clinical variants: tumor with a verrucous surface that is located in the lateral nail fold, as a band pattern suggesting wart or Bowen disease; a total dystrophy of the nail unit mimicking a squamous cell carcinoma; and pseudofibrokeratoma type. In the OM located on the ventral matrix, 3 new specific histologic variants were noted: pleomorphic OM, OM with a predominantly collagenous stroma, and superficial acral fibromyxoma-;like OM. OM is a benign tumor with a broader morphologic spectrum than previously thought. When the nail plate is not available, the immunohistochemistry can aid diagnosis by highlighting the peculiar immunophenotyping of OM, which expresses CD34 but not CD99, epithelial membrane antigen, S-100 protein, actin, and desmin.
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Onychomatricoma: Case report of an unusual subungual tumor with literature review
Article
  • Apr 2009
  • J CUTAN PATHOL
Onychomatricoma is rare subungual tumor of nail matrix origin. We report a 40-year-old white man with an onychomatricoma of the left index finger that highlights the characteristic clinical and pathological features and expands the known case material. We also review the published medical literature on the subject.
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