Skin nonmelanocytic tumor
Benign (nonmelanocytic) epidermal tumors or tumor-like lesions
Epidermolytic acanthoma
Authors: Simon F. Roy, M.D., Jennifer M. McNiff, M.D.
Resident / Fellow Advisory Board: Caroline I. Mullins, M.D.
Editorial Board Member: Kiran Motaparthi, M.D.
Last author update: 18 October 2021
Last staff update: 25 April 2022
Copyright: 2021-2025, PathologyOutlines.com, Inc.
PubMed Search: Epidermolytic acanthoma
Table of Contents
Definition / general | Essential features | ICD coding | Epidemiology | Sites | Pathophysiology | Clinical features | Diagnosis | Prognostic factors | Case reports | Treatment | Clinical images | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Videos | Sample pathology report | Differential diagnosis | Additional references | Board review style question #1 | Board review style answer #1 | Board review style question #2 | Board review style answer #2Cite this page: Roy SF, McNiff JM. Epidermolytic acanthoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skintumornonmelanocyticepidermolyticacanthoma.html. Accessed April 2nd, 2025.
Definition / general
- Cutaneous acanthotic benign lesion with epidermolytic hyperkeratosis spanning more than 50% of its surface
Essential features
- Solitary or multiple lesions with acanthosis and epidermolytic hyperkeratosis
- Epidermolytic hyperkeratosis spanning > 50% of the lesion surface
ICD coding
Epidemiology
- M = F (J Cutan Pathol 2019;46:305)
- Mean age: 58 years old (J Cutan Pathol 2019;46:305)
Sites
- Extragenital (67% of cases): head and neck, upper limbs, trunk or back, lower limbs (uncommon), oral (uncommon)
- Genital (33% of cases): vulvar, penile, perianal, perineal, scrotal
Pathophysiology
- Somatic hotspot mutations in the Arg156 position of KRT10, also known to cause epidermolytic ichthyosis (germline) (J Cutan Pathol 2020;47:524)
- Not HPV related (J Cutan Pathol 2020;47:524)
Clinical features
- Most frequently a single lesion but may be multiple (5% of instances) (J Cutan Pathol 2019;46:305)
- Erythematous, skin colored or brown papules or nodules with scale
- Multiple epidermolytic acanthomas are more likely to be found on genital sites
- Can be confused with condyloma (J Cutan Pathol 2019;46:305)
- May be pruritic
- Dermoscopy may show pearly white areas, irregular pigmented grooves and peripheral pigmented radial streak-like areas (J Am Acad Dermatol 2017;77:e37)
Diagnosis
- H&E stain with light microscopy
Prognostic factors
- Benign
Case reports
- 40 year old man with multiple epidermolytic acathomas on the fingers, mimicking flat warts (Case Rep Dermatol 2017;9:98)
- 49 year old man with multiple pruritic epidermolytic acanthomas on the scrotum (Actas Dermosifiliogr 2018;109:81)
- 56 year old man with epidermolytic acanthoma on the lower back and related dermoscopy findings (J Am Acad Dermatol 2017;77:e37)
- 57 year old man with solitary penile pidermolytic acanthoma mimicking condyloma (Dermatopathology (Basel) 2019;6:23)
- 58 year old woman with a solitary vulvar epidermolytic acanthoma mimicking condyloma (Int Angiol 1988;7:19)
- 71 year old Caucasian man with an oral solitary epidermolytic acanthoma (Oral Surg Oral Med Oral Pathol Oral Radiol 2019;128:e208)
Treatment
- Surgical excision
- Liquid nitrogen (Case Rep Dermatol 2017;9:98)
- Topical imiquimod (J Dermatol 2007;34:267)
- Topical calcipotriol (J Dermatol 2013;40:144)
Clinical images
Contributed by Simon F. Roy, M.D. and Jennifer M. McNiff, M.D.
Solitary epidermolytic acanthoma
Images hosted on other servers:
Multiple epidermolytic acanthomas on scrotum
Gross description
Microscopic (histologic) description
- Acanthosis and epidermolytic hyperkeratosis (covering > 50% of the lesion surface) (J Cutan Pathol 2019;46:305)
- Low power architecture generally resembles seborrheic keratosis (J Cutan Pathol 2019;46:305)
- Epidermolytic hyperkeratosis consists of lace-like degeneration of the midspinous epithelial layer, perinuclear vacuolization, epithelial eosinophilia and finely speckled keratohyaline granules (J Cutan Pathol 2019;46:305)
- 3 architectural patterns of solitary epidermolytic acanthoma have been described: papillomatous, cup shaped and acanthotic (J Eur Acad Dermatol Venereol 2011;25:175)
- Solitary and multiple epidermolytic acanthomas display similar histopathological findings (J Cutan Pathol 2019;46:305)
Microscopic (histologic) images
Contributed by Simon F. Roy, M.D. and Jennifer M. McNiff, M.D.
Papillomatous pattern
Cup-like / endophytic pattern
Positive stains
- Not usually performed
Videos
Epidermolytic hyperkeratosis
Sample pathology report
- Skin, left forearm, punch biopsy:
- Epidermolytic acanthoma
Differential diagnosis
- Seborrheic keratosis:
- Acanthosis and papillomatosis but no epidermolytic hyperkeratosis
- Focal incidental epidermolytic hyperkeratosis may be present
- Still classified as seborrheic keratosis if covering < 50% of the surface
- Verruca or condyloma:
- Hypergranulosis and finely speckled keratohyaline granules
- No lace-like reticular degeneration
- No dense cytoplasmic eosinophilia
- HPV induced
- Incidental epidermolytic hyperkeratosis in another acanthotic lesion:
- Epidermolytic hyperkeratosis is found spanning < 50% of the lesion surface
- Epidermolytic ichthyosis (formerly bullous congenital icthyosiform erythroderma):
- Generalized desquamating plaques rather than a solitary lesion
- Hereditary ichthyosiform condition due to alterations in keratin genes
- Overlapping histology with solitary epidermolytic acanthoma, clinicopathologic correlation is crucial
- Clear cell acanthoma:
- Pale epithelial cells with acanthosis but no epidermolytic hyperkeratosis
- Solitary keratosis with hypergranulotic dyscornification:
- Dense keratohyaline granules rather than finely speckled
- Both may display eosinophilic cytoplasm but perinuclear vacuolization is more characteristic of epidermolytic acanthoma
- Hypergranulotic dyscornification may be a focal incidental finding in other lesions
Additional references
Board review style question #1
What is the best diagnosis based on the images above, considering this is a solitary lesion?
- Clear cell acanthoma
- Epidermolytic acanthoma
- Epidermolytic ichthyosis
- Seborrheic keratosis
Board review style answer #1
B. Epidermolytic acanthoma. Epidermolytic acanthoma is an acanthotic benign lesion that displays epidermolytic hyperkeratosis on more than 50% of its surface. Clear cell acanthoma and seborrheic keratosis do not show epidermolytic hyperkeratosis on their surface. Epidermolytic ichthyosis does not present as a solitary lesion but rather as a hereditary generalized desquamative eruption.
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Board review style question #2
What is the histopathological epidermal reaction pattern seen in the image above?
- Acantholysis
- Dyskeratotic acantholysis
- Epidermal necrosis
- Epidermolytic hyperkeratosis
Board review style answer #2
D. Epidermolytic hyperkeratosis. Epidermolytic hyperkeratosis is the epidermal reaction pattern displayed here, with reticular (lace-like) clearing of the epidermis, dense eosinophilia of the keratinocytes and coarse keratohyalin granules. Acantholysis is rather a rounding of keratinocytes with detached intercellular attachments (desmosomes). Dyskeratotic acantholysis shows acantholysis in addition to dense eosinophilia of keratinocytes but no reticular degeneration of finely speckled keratohyalin granules.
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