074 ALK-positive desmoplastic Spitz naevus in a patient with corresponding ALK-positive anaplastic large cell lymphoma

Abstract

Aim:Spitz naevus is a benign melanocytic tumour with distinct histopathological features of spindle-shaped melanocytes. An understanding of genetic aberrations can help to characterise the different subsets of Spitzoid neoplasms. Anaplastic lymphoma kinase (ALK) is a tyrosine kinase receptor that was first described in the pathogenesis of anaplastic large cell lymphoma (ALCL). ALK mutations have been reported in up to 10% of Spitz tumours.This study describes the rare occurrence of an ALK mutation in two different diseases in the same patient – ALCL and Spitz naevus. Method:Presentation, management, and clinical outcomes were retrospectively reviewed for a patient with ALK-positive ALCL and ALK-positive Spitz naevus at a tertiary paediatric hospital. Result:The patient was a 14-year-old female with a 12-month history of a red-brown plaque on the right shoulder.This was on a background stage III ALCL treated with chemotherapy and stem cell transplantation. She underwent surgical excision of the skin lesion. Histopathological examination showed an ALK-positive desmoplastic Spitz naevus. A bone marrow aspirate and trephine (BMAT) of the right axillary lymph node at the time of ALCL diagnosis also revealed an ALK mutation. She is currently in remission 2 years post stem cell transplantation. Conclusion:Our case reports on a rare coincidence of a patient having the same mutation for two distinct disease processes. There has been one similarly reported case in the literature in a patient with ALK-positive cutaneous ALCL and Spitz naevi with the same fusion partner gene (TPM3). Whilst this occurrence is not fully understood, further studies may identify whether this is an independent coincidence in two different cell lineages, or a fragile site similarity which may predispose to the same translocation event.