Onychomatricoma: report of a case and its comparison with fibrokeratoma of the nailbed

Onychomatricoma: a case report with literature review

Onychomatricoma (OM) is a fibroepithelial tumor of nail matrix that occurs in the digits of both the hands and feet. This was first reported by Baran and Kint. They initially described 3 cases, all of which demonstrated a filamentous tumor of matrix tissue that resulted in a thickened funnel-shaped nail. Although apparently benign, it is subject to recurrence, and long-term follow-up is recommended because it is not known whether there is a conversion to malignancy. Even though this neoplasm was first described more than 18 years ago, there remains a dearth of case reports (currently fewer than 50) in the literature. This is a single case report and literature review. Levels of Evidence : Therapeutic, Level IV.

Onychomatricoma in the light of the microanatomy of the normal nail unit

Onychomatricoma (OM) is an uncommon benign tumor of the nail thought to exhibit differentiation limited toward the nail matrix. Four recent articles from our laboratory have shown, in some respect, a morphological and immunohistochemical homology between the nail unit and the hair follicle at the level of the matrix and isthmus. The purposes of this article are as follows: to investigate whether the sequential pattern of hair keratin expression in the normal nail matrix is maintained in OM, to compare and contrast follicular tumors with matrix differentiation in OM, and to furnish morphological and immunohistochemical markers of the onychogenic capacity of OM. Formalin-fixed paraffin sections from 6 OM were examined using specific keratin (K) antibodies for the matrix, nail bed, and nail isthmus. Hair keratins were expressed in a sequential pattern similar to normal nail matrix. In 3 cases where the cavities were completely lined by the fibroepithelial projections, the morphological aspect and the pattern of expression of K5, K17, K6, K16, and K75 suggested a differentiation toward the nail bed and the nail isthmus. This study shows for the first time that OM can recapitulate the entire nail unit with differentiation toward the nail bed and the nail isthmus. We have identified new histopathological and immunohistochemical features in OM, and we have abridged the diversity of its histological presentation in 2 main patterns: a lobulated or foliated pattern, observed principally on transverse section, and a "glove-finger" mono- or multidigitate pattern, observed mainly on longitudinal section. We have also concluded that OM is not a nail variant of trichoblastoma, pilomatricoma, or other pilar tumors. The concept of epithelial onychogenic tumor with onychogenic mesenchyme could shed more light about the true nature of this peculiar mixed tumor. However, the term OM is short and sanctioned by usage, which justifies keeping it.

Onychomatricoma: genome-wide analyses of a rare nail matrix tumor

BACKGROUND

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.

OBJECTIVE

We performed a genome-wide analysis of an OM, in an attempt to shed light on the mechanisms underlying its development.

METHODS

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.

RESULTS

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).

LIMITATIONS

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.

CONCLUSIONS

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.

Onychomatricoma: an unusual case of ungual pathology. Case report and review of the literature

Onychomatricoma represents a rare fibro-epithelial nail bed tumour. Numerous clinical variants of the condition have been described, and explicit diagnostic criteria have been recently developed. In this article, we outline the clinical and histopathological features of a case of onychomatricoma and review the literature with regards to the clinical presentation, differential diagnosis and management.

Nail unit tumors: a study of 234 patients in the dermatology department of the "Dr Manuel Gea González" General Hospital in Mexico City

BACKGROUND

The frequency of nail unit tumors is not well known because they are often misdiagnosed, and the clinical appearance of benign and malignant tumors is not characteristic.

PATIENTS AND METHODS

A total of 234 patients from the dermatology department of a general hospital in Mexico City were included in this study, from January 1982 to November 2006.

RESULTS

The tumors most frequently diagnosed were fibrous tumors (29.05%), osteocartilaginous tumors (21.79%), and myxoid pseudocysts (11.96%). Malignant melanoma occupied the fourth place (9.82%), and the second most frequent malignant tumor was squamous cell carcinoma (SCC; 4.70%). Among other tumors were glomus, neurofibromas, giant cell tumors of tendon sheath, and pyogenic granulomas. The nail plate was affected in 46.5% of the cases studied.

CONCLUSION

This study in a Mexican population sheds light on the frequency and the alterations produced by nail unit tumors, which we must keep in mind for a more accurate diagnosis.

Expression of Cadherin/Catenin Cell—Cell Adhesion Molecules in a Onychomatricoma

Onychomatricoma is a rare nail tumor with a distinctive architecture. Proximally, there are serum-filled invaginations of nail matrix epithelium into the stroma, and distally, dermal protrusions perforate the nail plate. Because other matrical tumors of follicular and odontogenic origin express nuclear β-catenin, we examined the expression of cadherin/catenin proteins in this onychomatricoma case. The patient presented with a toenail yellow streak, and the biopsy revealed an onychomatricoma. E-cadherin and β-catenin were at the cell membrane in the epithelial invaginations. P-cadherin was restricted to basal cells. In contrast to other matrical tumors, nuclear β-catenin was not present. These results suggest that onychomatricoma may lack the transcriptional activating role of β-catenin that characterizes follicular and odontogenic matrical tumors. This is the first report on the expression of cadherin/ catenin cell—cell adhesion proteins in this rare nail tumor.

Giant onychomatricoma: report of two cases with rare clinical presentation

BACKGROUND

Onychomatricoma was reported for the first time by Baran and Kint as a rare nail matrix tumor with specific clinical and histologic features, including a macroscopic appearance of filiform digitations originating from the nail matrix which are inserted in the nail plate.(1) The appearance of the lesion may resemble that of an "anemone." All previous reports have been mostly from Europe, with only one case from North America. These are the first case reports from Mexico. They show rare clinical characteristics, in particular tumor involving the entire nail matrix.

METHODS

Two cases are presented: Case 1, a 59-year-old man with a 2-year history of deformity of the entire nail apparatus of the right thumb, clinically suggestive of onychomatricoma; Case 2, a 45-year-old woman with a 3-year history of gradual nail dystrophy, initially misdiagnosed as onychomycosis and treated unsuccessfully for several months with antimycotics by a general physician. In both cases, the entire nail plate was affected and, because of the clinical appearance, nail exploration and excisional biopsy of the tumors at the nail matrix were performed.

RESULTS

During nail matrix surgical exploration, including avulsion of the nail plate, characteristic digitiform projections that were firmly attached to the nail plate were observed. In both cases, the entire nail matrix was affected, producing a giant form of onychomatricoma. Hematoxylin and eosin stain showed characteristic filiform projections that corresponded to the clinical appearance, with elongated epithelium from the nail matrix and fibromyxoid stroma with multiple basophilic cells, and typical clefts in between.

CONCLUSIONS

Onychomatricoma has a classical clinical appearance; however, it is difficult to identify, as it is not until surgery, when the typical filiform projections are more visible, that the diagnosis can be made. Onychomatricoma is a rare tumor. The involvement of the entire nail matrix, with secondary nail dystrophy, in both cases presented here makes them interesting case reports of this unusual form of tumor.

Onychomatricoma: first description in a child

Onychomatricoma is an uncommon benign tumor of the nail matrix, with peculiar clinical and histologic features and electron microscopic findings. The main clinical signs are longitudinal ridging, yellow coloration along the entire length of the nail plate with splinter hemorrhages in its proximal portion, and a tendency towards transverse overcurvature of the affected nails. We report onychomatricoma associated with onychomycosis in the same nail in a 4-year-old girl.

Common nail tumors

Nail abnormalities are varied and numerous. They include warts, keratoacanthomas, onychomatricomas, fibrokeratomas, osteochondromas, tumors (ie, glomus, giant cell, Koenen's, and others), and Bowen's disease. Although the gravity of these conditions may vary, prompt diagnosis and treatment is of the utmost importance. This article discusses the most common defects associated with the nail unit and its surrounding tissue, as well as the differential diagnosis and treatment of these conditions.

[Onychomatricoma, a rare lesion of the nail]

Onychomatricoma is a rare fibroepithelial lesion of the nail matrix with peculiar clinical and histological features. Clinically, it is characterized by a longitudinal band of yellow thickening of the nail plate with transverse overcurvature and splinter hemorrhages. Nail avulsion exposes a villous tumor of the matrix with filamentous digitations extending into multiple holes of the nail plate. Histologically, a thick keratogenous zone forms a thickened nail plate. The lesion in its proximal portion is characterized by deep epithelial invaginations and by a stroma organized in two layers. The distal zone corresponds to multiple fibroepithelial projections extending into the nail plate. The diagnosis can be difficult in the presence of misleading clinical features or when the specimen is incomplete or examined with an improper orientation. Surgical resection is the recommended treatment.

Unguioblastoma and unguioblastic fibroma--an expanded spectrum of onychomatricoma

Onychomatricoma is a rare tumor that appears to originate from cells of the nail matrix. Three cases of onychomatricoma that met Perrin et al.'s1 histologic criteria of onychomatricoma are described. However, using a single term to classify all three tumors ignores the apparent microscopic differences that exist among them. To demonstrate better the spectrum of so-called onychomatricoma and properly acknowledge the noticeable disparity among our cases, a series of terms is proposed. This terminology is based on the histologic spectrum of epithelial-stromal ratio of stromal cellularity and of extent nuclear pleomorphism. Use of such criteria has a precedent in the classification of follicular and odontogenic fibroepithelial neoplasms. This new nomenclature includes "unguioblastoma" for tumors with a predominant epithelial component and "unguioblastic fibroma" for tumors where a cellular stroma is more prominent and characteristic. The term "atypical unguioblastic fibroma" is used to describe a third rare neoplasm, in which the cellular stroma shows nuclear pleomorphism and atypia with an increase of mitotic activity.

The onychomatricoma: additional histologic criteria and immunohistochemical study

Onychomatricoma (OM) is a tumor of the nail matrix typified histologically by multiple distal fibroepithelial projections and a thick keratogenous zone forming multiple V-shaped invaginations at the level of epithelial ridges, with the formation of a thick nail plate. In its proximal portion, the thickness of the nail looks like a spur originating from the ventral part of the nail plate. In its distal part, beyond the lunula, the nail plate is globally thickened and filled with cavities containing serous fluid. Often, however, the pathologist is not provided with the nail plate. The diagnosis then rests on the presence of a fibroepithelial tumor. In this article the histologic criteria of OM without nail plate are refined and OM is characterized immunohistochemically using three tumors fixed in liquid nitrogen and examined separately from the nail plate. On longitudinal section OM without nail plate appears as a unique pedunculated fibroepithelial tumor i.e., the multiple distal epithelial digitations arranged along a transversal plane are not seen. The feature is reminiscent of fibrokeratoma. When OM is visualized in longitudinal section, 3 main criteria differentiate OM from fibrokeratoma: the presence of epithelial-lined invaginations around optical cavities, a stroma organized in 2 layers, and the absence of horny corn. Patterns of expression of cytokeratins and integrins in OM are identical to that observed in the normal nail matrix. Involucrin finds expression from the basal layer through to the top of the epithelium, where it is more marked and where transglutaminase 1 is restricted. Merkel cells detected by CK 20 are increased in number and sometimes disposed in clusters. The fibrous component of OM is composed of 2 layers: a superficial stroma made of numerous fines fibrils of collagen IV intermingled with collagen I, and deep stroma made principally of collagen I. Antibody AE13, specific to trichocytic keratins Ha 1-4, represent a good potential marker of OM. Its V-shaped expression in epithelium ridges offers early identification of the keratogenous zone of OM, on tumors separated from their nail plates and limited to their fibroepithelial components.