Collision tumors/lesions of the skinThis glossary term has not yet been described., detectable with dermoscopyThe examination of [skin lesions] with a 'dermatoscope'. This traditionally consists of a magnifier (typically x10), a non-polarised light source, a transparent plate and a liquid medium between the instrument and the skin, and allows inspection of skin lesions unobstructed by skin surface reflections. Modern dermatoscopes dispense with the use of liquid medium and instead use polarised light to cancel out skin surface reflections., can occur in all possible combinations of the different cells of the epidermal and/or dermal cell layers (Table 1, Figure 1) (1).
- Combinations of epidermal-epidermal collision tumors are more often found in UV-exposed skin areas in older patients than epidermal-dermal combinations.
- To diagnose correctly any possible collision tumor/lesion, the dermoscopic analysis of colorsThis glossary term has not yet been described. and differential structuresThis glossary term has not yet been described. must be perfomed in all four "quadrants" (2,3).
- The switch between polarized and non-polarized lightThis glossary term has not yet been described. might also be helpful (4,5).
Skin lesions or tumors with their original cell types of the different skin layers (focused only on skin lesions detectable by dermoscopy) (1).
Fig 3b: Description of Fig 3a: Seborrheic keratosis (upper part A) with a basal cell carcinomais the most common skin cancer, and one of the most common cancers in the United States. While BCC has a very low metastatic risk, this tumor can cause significant disfigurement by invading surrounding tissues (lower part B).
ReferencesThis is material contained in a footnote or bibliography holding further information.: 
- An Atlas of Dermoscopy, Second Edition. Marghoob A. et al. CRC Press; 2012.
- Blum A, Siggs G, Marghoob AA, et al. (2017) Collision skin lesions-results of a multicenter study of the International Dermoscopy Society (IDS). Dermatol Pract Concept 2017;7(4):12;51-62
- Braga JC, Scope A, Klaz I, Mecca P, Spencer P, Marghoob AA. Melanoma mimicking seborrheic keratosis: an error of perception precluding correct dermoscopic diagnosis. J Am Acad Dermatol 2008:58:875-880
- Kittler H, Marghoob AA, Argenziano G, et al. Standardization of terminology in dermoscopy/dermatoscopy: Results of the third consensus conference of the International Society of Dermoscopy. J Am Acad Dermatol. 2016;74:1093-1106
- Wang SQ, Dusza SW, Scope A, Braun RP, Kopf AW, Marghoob AA. Differences in dermoscopic images from nonpolarized dermo¬scope and polarized dermoscope influence the diagnostic accuracy and confidence level: a pilot study. Dermatol Surg 2008;34:1389-1395
- Pan Y, Gareau DS, Scope A, Rajadhyaksha M, Mullani NA, Mar¬ghoob AA. Polarized and nonpolarized dermoscopy: the explana¬tion for the observed differences. Arch Dermatol 2008;144:828-829.
- Blum A, Maltagliati-Holzner P, Deinlein T, Hofmann-Wellenhof R. Collision tumors in dermoscopy : A new challenge. Hautarzt 2018 May 4. doi: 10.1007/s00105-018-4172-z.