Collision lesions

From dermoscopedia
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Author(s) Andreas Blum · Rainer Hofmann · Florentia Dimitriou
Responsible author Andreas Blum→ send e-mail
Status unknown
Status update July 5, 2018
Status by Ralph P. Braun

Detectable by dermoscopy, Collision tumors/lesions of the skin can occur in all possible combinations of the different growths of the epidermal and/or dermal cell layers (Table 1 & Figure 1)[1].

  • They are associated with advancing age and cumulative UV-exposure[2].
  • Compared with combinations of epidermal-dermal collision tumors, epidermal-epidermal collision tumors are more likely to be found in older patients and on the head and neck areas. In addtion, Collision tumors with a basal cell carcinoma component are more common on the head and neck compared to collision tumors with a melanocytic component that are more common on the trunk[2].
  • Collision tumors pose a diagnostic challenge. To correctly diagnose any possible collision tumor/lesion, the dermoscopic analysis of colors and structures must be performed in all four "quadrants" of the inspected lesion[3].
  • Using both polarized and non-polarized dermoscopy may be helpful in the diagnosis of these lesions[4][5].

Table 1 - Skin lesions or tumors with their original cell types of the different skin layers (focused only on skin lesions detectable by dermoscopy).[2]

Layer of the Skin Cell Type or Functional Structure Associated Proliferations / Neoplasms
Epidermis Keratinocytes Solar lentigo

Seborrheic keratosis
Actinic keratosis
Bowen's disease
Squamous cell carcinoma

Basal cell layer (non-differentiated folliculo-sebaceous-apocrine germ) Trichoblastoma

Basal cell carcinoma

Melanocytes Melanocytic nevus


Merkel cells Merkel cell carcinoma
Dermis Blood capillaries Angioma
Melanocytes Melanocytic (dermal or blue) nevus


Fibroblasts Dermatofibroma

Dermatofibrosarcoma protuberans

Non-Langerhans cells/histiocystes Xanthogranuloma
Infundibulo-follicular-sebaceous unit Sebaceous hyperplasia

Milia cyst
Adnexal (benign or malignant) tumor

Myocytes Kaposi sarcoma

  1. An Atlas of Dermoscopy, Second Edition. Marghoob A. et al. CRC Press; 2012.
  2. 2.0 2.1 2.2 Blum et al.: Collision skin lesions-results of a multicenter study of the International Dermoscopy Society (IDS). Dermatol Pract Concept 2017;7:51-62. PMID: 29230351. DOI.
  3. Braga et al.: Melanoma mimicking seborrheic keratosis: an error of perception precluding correct dermoscopic diagnosis. J. Am. Acad. Dermatol. 2008;58:875-80. PMID: 18328596. DOI.
  4. Kittler 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;74:1093-106. PMID: 26896294. DOI.
  5. Wang et al.: Differences in dermoscopic images from nonpolarized dermoscope and polarized dermoscope influence the diagnostic accuracy and confidence level: a pilot study. Dermatol Surg 2008;34:1389-95. PMID: 18637816. DOI.
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