A report describes a case of a 51-year-old male who complained of a gradually progressive blackish discoloration of the left thumbnail for 10 months. Associated history of insidious onset gradually progressive swelling of the distal aspect of left thumb was also given. There was mild pain, no history of any trauma before the complaints, and no discharge or itching. He took many oral and topical medicines including several courses of oral antifungals without any relief.

Examination showed diffuse mildly tender swelling in the distal part of the left thumb, distal to the interphalangeal joint, with hyperpigmented and dystrophic overlying nail plate. Hyperpigmentation was also seen on the proximal nail fold, hyponychium and periungual areas (positive Hutchinson′s sign). Islands of black necrotic granulation tissue with scant purulent non-foul smelling discharge in between the layers of the dystrophic nail plate were also seen. No regional lymphadenopathy was present.

Systemic examination was normal. Biopsy was taken from left thumbnail bed, which on histopathological examination revealed traits of malignant melanoma. Other investigations like hemogram, urinalysis, liver and renal functions, ultrasound abdomen and CT scan abdomen were within normal ranges. No features of metastasis were seen in the detailed evaluation including a PET scan.

Excision of the entire lesion along with disarticulation at the interphalangeal joint was carried out. Resected margins were free of tumor tissue. Histopathology revealed layers of cells with varied shapes. The spindle cells showed scanty cytoplasm, pleomorphic oval to spindle hyperchromatic nuclei, with some angulated nuclei. Some polygonal cells had large coarse nuclei and prominent macronucleoli. The intracytoplasmic golden-brown pigment was seen in many cells. Also, the areas of necrosis and mitotic figures were seen.  

The histopathological features prompted the final diagnosis as malignant melanoma.

Source: Verma R, Kakkar S, Vasudevan B, et al. A rare case of subungual melanoma. Indian J Dermatol. 2015;60(2):188-90.