Skin nonmelanocytic tumor
Benign (nonmelanotic) epidermal tumors or tumor-like lesions
Clear cell acanthoma
Last author update: 1 May 2016
Last staff update: 25 May 2023 (update in progress)
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PubMed Search: Clear cell acanthoma [title]
Table of Contents
Definition / general | Terminology | Sites | Pathophysiology | Etiology | Clinical features | Case reports | Treatment | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Negative stains | Electron microscopy description | Differential diagnosisCite this page: Sriharan A, Shalin SC. Clear cell acanthoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skintumornonmelanocyticclearcellacanthoma.html. Accessed June 4th, 2023.
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
- 33 year old woman with clear cell acanthoma developing in epidermal nevus (J Dermatol 1997;24:601)
- Multiple clear cell acanthomas and ichthyosis (Arch Dermatol 1972;105:371)
- Clear cell acanthoma developing on a psoriatic plaque (Br J Dermatol 2000;142:842)
- Polypous clear cell acanthoma (Am J Dermatopathol 1990;12:393)
- Clear cell acanthoma presenting as nipple eczema (Br J Dermatol 1999;141:950)
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
Clear cell acanthoma
Clear cell acanthoma
Positive stains
Negative stains
- Carcinoembryonic antigen (CEA)
- Phosphorylase negative (cytochemical stain), except in the basal layer
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
