Skin nonmelanocytic tumor
Benign (nonmelanotic) epidermal tumors or tumor-like lesions
Clear cell acanthoma


Topic Completed: 1 May 2016

Minor changes: 23 September 2020

Copyright: 2003-2020, PathologyOutlines.com, Inc.

PubMed Search: Clear cell acanthoma [title]

Aravindhan Sriharan, M.D.
Sara C. Shalin, M.D., Ph.D.
Page views in 2019: 8,383
Page views in 2020 to date: 5,616
Cite this page: Sriharan A, Shalin SC. Clear cell acanthoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skintumornonmelanocyticclearcellacanthoma.html. Accessed October 21st, 2020.
Definition / general
  • A small sharply demarcated benign epidermal tumor, typically of the leg or arm, with acanthosis and accumulation of glycogen in keratinocytes having pale staining cytoplasm (Clear cell acanthoma - Farlex Partner Medical Dictionary)
  • Acanthoma: broad term for benign tumor of keratinocytes
  • Classically seen on legs, no known gender predilection, rarely may be multiple (eruptive)
  • Average age of onset: 52 years
Terminology
  • Pale Cell Acanthoma (of Degos)
  • Degos Acanthoma
  • Acanthome cellules claires of Degos and Civatte
Sites
  • Distal lower extremities of middle aged and older individuals
  • Other sites reported
Pathophysiology
  • Upregulation of KGF (Keratinocyte Growth Factor) may cause the cell proliferation
  • Defect in phosphorylase enzyme leads to intracellular glycogen accumulation
Etiology
  • Precise etiology unknown
  • Has been regarded as:
    • Inflammatory epithelial hyperplasia (reactive)
    • Hamartoma
    • Variation of seborrheic keratosis
Clinical features
  • Well demarcated, pink to tan papule or plaque
  • Polypoid, pigmented and giant variants (up to 6 cm) have been described
  • Often peripheral rim of scale and central erythematous area with puncta that bleed easily upon trauma
  • Under dermoscopy:
    • Dotted blood vessels are lined up in strings with white surrounding halo
    • Blood is crusted at periphery of lesion
Case reports
Treatment
  • Surgical excision is the standard of care, and is curative
  • Cases have been successfully treated by carbon dioxide laser ablation (Dermatol Surg 2005;31:1355)
Gross description
  • Pink to brown, flat or slightly raised plaque or nodule
Microscopic (histologic) description
  • Bland, intraepithelial tumor of clear keratinocytes with abrupt transition to and from normal epidermis
  • Often in a pattern of psoriasiform hyperplasia, hypogranulosis and neutrophils throughout the epidermis and in the stratum corneum
  • Typically lacks the thinning of the suprapapillary plate seen in psoriasis
  • May be colonized by melanocytes or have parakeratosis
  • Often the vessels within the dermal papillae are dilated, tortuous and run vertically up the papillae
  • Often spares hair follicles / adnexal structures.
  • Some cases have hyperplasia of underlying sweat ducts
Microscopic (histologic) images

Contributed by Mark R. Wick, M.D. and J. Michael Magill, Jr., M.D.
PAS, breast skin PAS, breast skin

PAS, breast skin

Clear cell acanthoma Clear cell acanthoma Clear cell acanthoma Clear cell acanthoma

Clear cell acanthoma


Clear cell acanthoma Clear cell acanthoma Clear cell acanthoma

Clear cell acanthoma

Positive stains
  • PAS (diastase sensitive due to glycogen accumulation)
  • Keratin, filaggrin and involucrin
  • Strong diffuse EMA (epithelial membrane antigen) positivity
Negative stains
Electron microscopy description
  • Abundant glycogen containing granules, except in basal keratinocytes
  • The granules are concentrated around nuclei in the lower layers of the epidermis; in upper layers they are more numerous and center on cytoplasmic tonofilaments
  • Melanosomes are abundant within melanocytes, but are distinctly absent in keratinocytes, indicating a defect in the transfer mechanism between melanocytes and keratinocytes
Differential diagnosis
  • Bowen disease (squamous cell carcinoma in situ): has full thickness cytologic atypia
  • Poroma: lacks cytoplasmic glycogen, has basaloid, polygonal nuclei and evidence of ductular differentiation
  • Psoriasis vulgaris: lacks the sharply demarcated lateral boundaries and glycogenation; has thinner suprapapillary plates; lacks string-like arrangement of vessels on dermoscopy
  • Seborrheic keratosis: lacks cytoplasmic glycogen
Back to top
Image 01 Image 02