Clear cell acanthoma

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Main PageBenign lesionsClear cell acanthoma
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Description This chapter describes the dermoscopy of clear cell acanthoma
Author(s) N. N.
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Status update March 25, 2023
Status by Ralph P. Braun


Also known as "Acanthome cellules claires of Degos and Civatte", "Degos acanthoma," and "Pale cell acanthoma", clear cell acanthoma is a benign clinical and histological lesion initially described as neoplastic, which some authors now regard to as a reactive dermatosis. It usually presents as a moist solitary firm, brown-red, well-circumscribed, 5 mm to 2 cm nodule or plaque on the lower extremities of middle-aged to elderly individuals. The lesion has a crusted, scaly peripheral collarette and vascular puncta on the surface. It is characterized by slow growth, and may persist for years [1].

Dermoscopic features

'String of pearls'

Even though clear cell acanthoma has a non-specific clinical appearance, it has a relatively specific and easy to recognize dermoscopic feature called 'string of pearls', referring to dotted vessels that are arranged in a linear of serpiginous pattern [2]. The linear formations tend to coalesce into a reticular pattern, covering whole or part of the lesion [1]. The 'string of pearls' sign was found to be related to angio-eccrine hyperplasia and vascular hyperplasia of the papillary dermis, corresponding to the capillaries oriented perpendicular within the elongated dermal papillae [3].

Clear cell acanthoma.jpg

Additional dermoscopic features [1]

  • Pale pink background (90% of cases)
  • Shiny white lines (60% of cases)
  • Glomerular vessels (55% of cases)
  • Collarette of translucent scale around the periphery of the lesion (40% of cases)
  • Haemorrhagic areas (35% of cases)
  • Orange crusts (15% of cases)

CP (5).JPG

Differential diagnosis

The clinical differential diagnosis includes [4]:

  • Dermatofibroma
  • Inflamed seborrheic keratosis
  • Pyogenic granuloma
  • Actinic keratosis
  • Basal cell carcinoma
  • Squamous cell carcinoma
  • Verruca vulgaris
  • Psoriasis
  • Eccrine poroma
  • Clear cell hidradenoma
  • Melanoma.

In a recent report it was demonstrated that the 'string of pearls' sign can be seen with other epidermal lesions, as two seborrheic keratoses and one lichen planus-like keratosis presented with the classic 'string of pearls' sign. [5]

  1. 1.0 1.1 1.2 Lyons et al.: Dermoscopic features of clear cell acanthoma: five new cases and a review of existing published cases. Australas. J. Dermatol. 2015;56:206-11. PMID: 25495637. DOI.
  2. Tiodorovic-Zivkovic et al.: Dermoscopy of clear cell acanthoma. J. Am. Acad. Dermatol. 2015;72:S47-9. PMID: 25500041. DOI.
  3. Paolino et al.: Clinicopathological and dermoscopic features of angio-eccrine hyperplasia in clear cell acanthoma. J. Am. Acad. Dermatol. 2016;74:1259-1261.e3. PMID: 27185430. DOI.
  4. Tiodorovic-Zivkovic et al.: Dermoscopy of clear cell acanthoma. J. Am. Acad. Dermatol. 2015;72:S47-9. PMID: 25500041. DOI.
  5. Espinosa et al.: "String of pearls pattern": report of three cases of non clear-cell acanthoma. An Bras Dermatol 2017;92:142-144. PMID: 29267474. DOI.
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