case_images: PMC9883383_01
case_images: (A) Longitudinal melanonychia on the fifth toe of the left foot (black arrow). (B) Onychoscopy of the toe showing regular, parallel, brown-pigmented lines forming a band along the nail plate (black arrow). (C) Intraoperative image showing the presence of pigment on the distal nail matrix (black arrow).
case_images: cureus-0015-00000034292-i01.jpg
case_images: PMC9883383_01_cureus-0015-00000034292-i01.jpg
case_images: FIG1
case_images: No periungual brownish pigmentation of the cuticle (micro-Hutchinson's sign) was observed (Figure 1, Panel B). After completely removing the nail plate, the presence of pigment on the distal nail matrix was evident; therefore, an excisional biopsy of the pigmented lesion was performed (Figure 1, Panel C).
case_images: (A) Hematoxylin and eosin stain, x4. Microscopy of the nail matrix tissue specimen shows epithelial acanthosis (black brackets) and pagetoid upward migration of individual epidermal cells with clear cytoplasm and groups of these cells in a spindle shape. (B) Hematoxylin and eosin stain, x10 and x40, respectively. Microscopy of the nail matrix tissue specimen with greater magnification shows the individual epidermal cells with clear cytoplasm (red arrows).
case_images: cureus-0015-00000034292-i02.jpg
case_images: PMC9883383_01_cureus-0015-00000034292-i02.jpg
case_images: FIG2
case_images: The histopathology of the tissue specimen reported a nail matrix with epithelial acanthosis and pagetoid upward migration of epidermal cells with clear cytoplasm (Figure 2, Panels A and B).
case_images: Immunohistochemistry showing Melan-A-positive cells and HMB45-positive cells (black arrows)
case_images: cureus-0015-00000034292-i03.jpg
case_images: PMC9883383_01_cureus-0015-00000034292-i03.jpg
case_images: FIG3
case_images: This showed Melan-A-positive cells and HMB45-positive cells (black arrows) (Figure 3).