Acquired Localized (Monodactylous) Longitudinal Pachyonychia and Onychocytic Carcinoma In Situ (2 Cases): Part II.

The authors have recently proposed to use the name pachyonychia as an umbrella term that includes 2 distinctly different entities in the form of congenital pachyonychia and acquired longitudinal pachyonychia. Congenital pachyonychia is defined by a diffuse hyperkeratosis of the nail bed. Acquired longitudinal pachyonychia correspond to the true definition of pachyonychia, that is, a thickened nail plate without subungual keratosis. Acquired (monodactylous) pachyonychia can be diffuse typifying onychomatricoma or localized as a longitudinal band with three etiological possibilities: onychomatricoma, onychocytic matricoma, and onychocytic carcinoma. On histopathological examination, onychomatricoma is a fibroepithelial tumor; conversely, onychocytic matricoma and carcinoma are purely epithelial tumors. The purpose of this study was to present the clinical, pathological, and immunohistochemical profiles of 2 cases of in situ onychocytic carcinoma, to discuss the role of high-risk human papillomavirus in the pathogenesis of this tumor, and to confirm the interest value of nail clipping microscopy in the surgical planning of the acquired (monodactylous) pachyonychia band pattern. Two men were referred for a longitudinal thickening of the lateral part of the nail plate of their fingers. The bands were yellowish with a faint to dominant black coloration. Nail clippings were obtained before excision in one case; the nail plate was thickened with minute holes in a honeycomb pattern. Nail biopsy specimens revealed an onychocytic carcinoma with epithelial projections inducing active production of the nail plate and multiple minute cavitations into the thick nail plate. Hair-related keratins were expressed in all specimens. One tumor expressed p16 in a diffuse pattern, whereas the other showed an unspecific faint patchy staining. p53 was negative. A clinical finding of longitudinal pachyonychia, which by nail clipping microscopy contains small cavities in a honeycomb-like pattern, should be considered an alert to the possibility of a malignant lesions.

Acquired Localized Longitudinal Pachyonychia and Onychomatrical Tumors: A Comparative Study to Onychomatricomas (5 Cases) and Onychocytic Matricomas (4 Cases).

BACKGROUND: Besides onychomatricoma (OM), which shows a clinical band pattern of nail plate thickening, 2 new onychomatrical tumors with this clinical feature have recently been described: onychocytic matricoma (OCM) and in situ onychocytic carcinoma. OBJECTIVE: The purpose of this study was to present 4 cases of OCMs and compare their clinical and histopathologic characteristics with usual OMs. METHODS: We studied 4 cases of OCMs with nail clipping in 3 cases and an extensive immunohistochemical study for hair-related keratins and epithelial keratins. Nail clipping of OCMs was compared with the distal nail plate of 5 cases of OMs. RESULTS: All cases showed an acquired localized longitudinal band pattern of a thickened nail plate with yellow discoloration in 2 cases and a black streak in 2 cases. All cases showed a V-shaped keratogenous epithelial tumor with a papillomatous pattern of growth. The nail plate was thickened with small holes in a honeycomb pattern. In contrast, the 5 OMs showed the classical pattern of a panonychoma fibropapilliferum. The nail plate showed large cavities in a honeycomb pattern. CONCLUSIONS: This case series raises awareness of the clinical value of longitudinal pachyonychia coupled with nail clipping in the early detection of onychomatrical tumors as generic diagnosis with a limited differential diagnosis and a simple therapeutic approach. Nail clipping could be an aid in the surgical planning of onychomatrical tumor. A diagnosis of a benign growth could be suggested when the average dimensions of cavities are superior to 0.15 mm sparing the patient from an excisional procedure with its risk of subsequent permanent nail dystrophy. In contrast, nail clipping with a honeycomb pattern of minute cavities with average dimension inferior to 0.10 mm should prompt a biopsy of the distal matrix to rule out a malignant lesion.

CO2 Laser-Assisted Nail Sampling for Mycological Testing in Onychomycosis.

Introduction: Onychomycosis is the most common nail infection, predominantly caused by Trichophyton spp., and is divided into four main types. Confirmatory testing is crucial, but obtaining an adequate sample may be challenging. We suggest the use of carbon dioxide (CO2) laser for painlessly detaching the nail plate during mycological examination and ensuring a sufficient specimen. Methods: We retrospectively enrolled 25 patients with distolateral onychomycosis, treated according to the following protocol: (1) multiple passes of CO2 laser at 10 W in continuous mode along the proximal border of the affected nail plate; (2) the nail plate was gently cut; (3) the nail bed was curetted; (4) subungual debris and plate fragments were collected for KOH test and culture. Results: The mean visual analog score (VAS) for pain experienced during the procedure was 0.7 (SD: 2.1), indicating that the sampling was relatively painless for the majority of patients. There were no permanent changes observed in the nail unit of any patients during the follow-up visits as a result of using the CO2 laser. Conclusion: We firmly believe that the use of lasers offers numerous advantages, including ease of use, reduced pain perception, and the ability to target the proximal margin of fungal infections where viable hyphae are significantly represented.

Onychocytic matricoma presenting as pachymelanonychia longitudinal. A new entity (report of five cases).

Among the tumors of the epidermal appendages, only rare tumors have been proved as differentiating in the direction of the nail. Beside onychomatricoma, we report a new matrical tumor of the nail: onychocytic matricoma (acanthoma of the nail matrix producing onychocytes). The main differential diagnosis of onychocytic matricoma is seborrheic keratosis. However, if attention is paid to the nature of the different layers of the tumor and the peculiar microanatomy of the nail matrix, the differentiation is not difficult. Onychocytic matricoma is a localized (monodactylous) longitudinal melanonychia which is slightly raised. The term pachymelanonychia is used to define the 2 clinical features of the tumor. Pachyonychia indicate a localized thickening of the nail plate, and melanonychia indicate its longitudinal pigmented band. Onychocytic matricoma is composed of a basal compartment with a varying admixture of prekeratogenous cells and keratogenous cells. Endokeratinization originating in the deep portion of the tumor and nests of prekeratogenous and keratogenous cells in concentric arrangement are a characteristic feature. Three major patterns can be identified as follows: acanthotic, papillomatous, keratogenous type with retarded maturation. Given the peculiar thickening of the nail plate observed both in pigmented onychomatricoma and onychocytic matricoma, the term pachymelanonychia longitudinal could be proposed to specify clinically these 2 lesions, which the clinician sometimes mistakes for melanoma.

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.