Skin - Nonmelanocytic tumors
Adnexal tumors - eccrine sweat glands
Clear cell acanthoma

Author: Aravindhan Sriharan, M.D. (see Authors page)
Editor: Sara Shalin, M.D., Ph.D.

Revised: 10 June 2016, last major update May 2016

Copyright: (c) 2003-2016, PathologyOutlines.com, Inc.

PubMed Search: Clear cell acanthoma [title]
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)
Clinical Images

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Various images

Gross Description
  • Pink to brown, flat or slightly raised plaque or nodule
Micro 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
Micro Images

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PAS, breast skin
Contributed by: Dr. Mark R. Wick




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Contributed by: Dr. J. Michael Magill, Jr.

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