Unveiling Giant Onychomatricoma: A Diagnostic and Therapeutic Challenge

Onychomatricoma is a rare benign tumor of the nail matrix that is often misdiagnosed due to its resemblance to other nail conditions, particularly onychomycosis. A giant variant, which affects the entire nail structure, is even more uncommon, with fewer than 20 cases documented. We present the case of a 62-year-old male with a 5-year history of a slow-growing, asymptomatic tumor on the third nail of his left hand. Clinical examination revealed a papillomatous mass originating from the nail matrix, accompanied by nail thickening and xanthonychia. Dermoscopy showed longitudinal yellow, white, and gray lines, splinter hemorrhages, and a honeycomb pattern. Mycological testing suggested onychomycosis, but due to the size and persistence of the lesion, a multidisciplinary team recommended a complete nail avulsion and proximal matricectomy. Histopathological analysis revealed fibroepithelial projections covered by squamous epithelium and thickened nail plate fragments, confirming the diagnosis of giant onychomatricoma. The patient underwent surgical management and has shown no signs of recurrence after 2 years of follow-up. This case highlights the diagnostic and therapeutic challenges posed by giant onychomatricoma, particularly when coexisting with fungal infection. It also underscores the need for thorough clinical, dermoscopic, and histopathological evaluation in cases of chronic nail deformities.