Research interest in dermoscopy has accelerated, but the complete dermoscopic image sets used for inter-observer investigations for skin tumors are not often shared to the reader. The aim of this systematic review was to analyze what proportion of images depicting skin tumors are shared in the manuscripts of studies investigating inter-observer variation in the assessment of dermoscopic features and/or patterns. The Embase, MEDLINE, and Scopus databases were screened for eligible studies published from inception to July 2, 2020. For included investigations we extracted the proportion of lesion images presented in the manuscripts and or supplements. Overall, we included 61 studies (52 original investigations and 9 concise reports) in the time period of 1997 to 2020. These investigations combined, included 14,124 skin tumors of which 373 (3%) images were shared. Since data sharing must be promoted, this investigation should be a wake-up call for the dermatology research community and editorial offices.