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
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