A rare acral lesion with parallel-ridge pattern on dermoscopy

A parallel-ridge pattern on dermoscopy is often associated with early invasive melanoma or melanoma-in-situ of acral sites. Here, we present a case of pagetoid dyskeratosis with a parallel-ridge pattern on dermoscopy, mimicking acral melanoma-in-situ.
Pagetoid dyskeratosis is a benign incidental histological finding in various skin conditions, often located in intertriginous areas. Friction and moisture are thought to be triggers, although the exact cause is unclear.
A 34 year old builder presented with a 6-month history of an enlarging rusty-brown discolouration on the palmar aspect of his right little fingertip. There was no associated nail deformity or discolouration. He was a non-smoker. Dermoscopy showed a parallel-ridge pattern, which raised the suspicion of a melanoma arising in an acral site. Punch biopsy of the lesion showed epidermal hyperplasia, compact hyperkeratosis, hypergranulosis and scattered large cells with vacuolated cytoplasm in the epidermis. There was no evidence of melanocytic proliferation along the dermo-epidermal junction. Immuno-histochemical staining of the epidermal clear cells were negative for S100, SOX10, CEA, Cytokeratins 5,7 and CAM5.2, consistent with a diagnosis of Pagetoid dyskeratosis.
There is limited amount of published literature on pagetoid dyskeratosis of the hands and palms1 but it is now slowly being recognised as a separate entity. This condition requires no specific treatment and is thought to be friction-induced. It should be considered as a differential diagnosis in acral lesions displaying the parallel-ridge pattern on dermoscopy.
1. Toyonaga E, Inokuma D, Abe Y et al. Pagetoid dyskeratosis with parallel ridge pattern under dermoscopy. JAMA dermatology. 2013;149(1):109-11.

Dr. Priyamvada Sobarun

Queensland Institute of Dermatology, Brisbane QLD

I am a final year dermatology trainee from New Zealand, currently doing my overseas training at the Queensland Institute of Dermatology and Princess Alexandra Hospital in Brisbane. I am also involved in various clinical research projects at the Princess Alexandra Hospital where I am working with Prof Peter Soyer. I am interested in all aspects of dermatology, in particular, medical dermatology, dermoscopy and skin cancer management.