The diagnostic challenge of amelanotic melanoma – case reports and short review of the literature

Introduction Cutaneous melanoma represents a very aggressive type of cancer that has one of the fastest growing incidences worldwide, with over 150000 new cases estimated in developing countries in 2010 (Jemal et al 2011). Although it represents only 10% of the total cutaneous malignant tumours, melanoma is responsible for over 90% of the deaths caused by these tumours (Jemal et al 2011). Amelanotic melanoma (AM) accounts for 2-8% of all melanomas (Jaimes et al 2012) and represent an atypical form of presentation that may not be easily recognized as malignant melanoma (McClain et al 2012). Studies show that survival after diagnosis of amelanotic melanoma is poorer than after pigmented melanoma, probably because the diagnosis is difficult and is made in more advanced stage (Thomas et al 2014). Clinically, the term of AM reffers to any melanoma lacking pigment, however there are also melanomas that produce low-levels of melanin (hypomelanotic melanoma HM) and may appear to have no pigment (Jaimes et al 2012). Because of their lack of pigment, such lesions may be misdiagnosed as other benign or malignant skin tumors or even as inflamatory disorders, and the treatment can be delayed until advanced stages when the lesion becames nodular, vascular or ulcerated (Bono et al 2001). Dermatoscopy is an in vivo, non-invasive technique that allows a 10x magnification of the skin which enables the clinician to analyse the morphological structures within pigmented lesions that are not visible with the naked eye, structures with a welldefined histological correspondent. Various studies have demonstrated the improved capacity of dermatoscopy in differentiating benign lesions from malignant ones, bringing a valuable contribution to the early diagnosis of melanoma (Kittler 2008; Argenziano et al 2012; Argenziano et al 1997). Although dermoscopic evaluation has been shown to improve the accuracy of pigmented melanoma diagnosis compared with naked eye examination, less literature is found regarding melanomas lacking significant pigment. Still, dermoscopic evaluation has been shown to be superior to naked eye examination for the diagnosis of amelanotic or hypomelanotic melanoma (Pizzichetta et al 2004; de Giorgi et al 2006) We report two unusual presentations of amelanotic melanoma resembling squamous cell carcinoma and basal cell carcinoma, two types of malignant skin tumours with completely different prognosis from AM. Both patients signed an informed consent for their data and pictures to be used for scientific purposes.