Onychocytic matricoma

Abstract

Onychocytic matricoma is a newly described tumor of the nail matrix. Clinically, it presents with localized thickening of the nail plate and melanonychia. Histologically, it represents a benign acanthoma of onychocytes. There are 8 cases reported in the literature. A 12-year-old girl presented with localized melanonychia and concurrent thickening of the nail plate restricted to the area of pigmentation affecting the right thumb, with no history of trauma or pain. We report a case of this rare tumor occurring in late childhood and provide a comprehensive review of its clinical presentation and differential diagnosis. Both clinicians and dermatopathologists should be aware of the presentation of onychocytic matricoma and include it in their scope of diagnosis of longitudinal nail bands.

Ungual seborrheic keratosis with longitudinal melanonychia: A case report

“…We suggest that the dermoscopic finding of milia‐like cysts may be useful for the diagnosis of ungual SK, although clinically and pathologically it is often difficult to differentiate between ungual SK and OCM. Some dermoscopic findings of OCM were similar to those of ungual SK, such as longitudinal streaks with various colors (white, yellow, tan, and dark brown), splinter hemorrhages, 12 and localized thickening of the nail plate with subungual hyperkeratosis at the hyponychium 13 . On the contrary, the tip of OCM shows a honeycomb‐like cavity with thickening and deformation of the nail plate, which is more pronounced in the late stages 14 .…”

“…Some dermoscopic findings of OCM were similar to those of ungual SK, such as longitudinal streaks with various colors (white, yellow, tan, and dark brown), splinter hemorrhages, 12 and localized thickening of the nail plate with subungual hyperkeratosis at the hyponychium. 13 On the contrary, the tip of OCM shows a honeycomb-like cavity with thickening and deformation of the nail plate, which is more pronounced in the late stages. 14 Therefore, late lesions of OCM are likely to be differentiated by observation of the nail apex.…”

Nail‐plate dystrophy of the fifth toenail: thinking outside the box

“…The median age of presentation is the fifth decade of life, but a case in a 12-year-old patient has been reported. 3,6 Diagnosis of OCM is challenging. OCM presents with nail-plate abnormalities, including a pigmented, thickened and rough surface associated with increased transverse curvature (pachymelanonychia).…”

“…In contrast to onychocytic carcinoma, OCM does not display cellular atypia, nuclear pleomorphism, prominent nucleoli or mitotic figures. 5,6 OCM differs from onychopapilloma that is a tumour of the distal matrix affecting the entire nail unit and showing epithelial hyperplasia, deep clefts and nail bed papillomatosis, whereas onychomatricoma is a fibroepithelial tumour and shows nail-bed papillomatosis with a cellular stroma and collagen fibres.…”

“…Onychocytic matricoma is more common in women, and arises more frequently in the fingernails compared with the toenails. The median age of presentation is the fifth decade of life, but a case in a 12‐year‐old patient has been reported 3,6 …”