SAMPUS, MELTUMP and THIMUMP - Diagnostic Categories Characterized by Uncertain Biological Behavior

In the dermatopathological practice, there is a group of atypical melanocytic lesions with borderline histological features between benign simulants and malignant melanoma (MM), due to conflicting diagnostic criteria and inter-observer disagreement. In these cases, the dermatopathologist is authorized to seek consult with an established expert in the field, but even the most experienced specialist may not be sure about the correct diagnosis and the subsequent biological behavior. There is general consensus among qualified dermatopathologists that can be helpful to insert these ambiguous cases into two diagnostic categories: SAMPUS (Superficial Atypical Melanocytic Proliferations of Unknown Significance) and MELTUMP (MELanocytic Tumors of Uncertain Malignant Potential). According to the conception of MM progression through two phases, the radial growth phase and the vertical growth phase, it is possible to identify a novel subtype of thin melanoma (THIM) with uncertain metastatic potential, due to the presence of extensive regression ( 75% of the lesion volume), which we here define with the acronym THIMUMP (THIn Melanoma of Uncertain Metastatic Potential) for the first time in literature.Key words: malignant melanoma - thin melanoma - histology.