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This general category of skin tumors is a general term for benign tumors of epidermal keratinocytes. The unifying characteristics include a benign behavior, epidermal acanthosis or hyperplasia, and lack of dysplasia. Some investigators lump seborrheic keratosis with this group.


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ACANTHOLYTIC ACANTHOMA Solitary tumor on trunk of older patients. Multiple lesions may be seen in renal transplant patients.

Histology shows hyperkeratosis, papillomatosis, acanthosis, and variable acantholysis.
Acantholytic dyskeratotic acanthoma: a variant of a benign keratosis.

Department of Dermatology, Yale University School of Medicine, New Haven, CT, USA.

J Cutan Pathol. 2008 Mar;35(3):298-301. Abstract quote

Acantholytic acanthoma was originally described as a solitary lesion displaying histologic features of acantholysis without dyskeratosis. Solitary, non-genital lesions displaying confluent acantholysis and dyskeratosis have not been well described in the literature, clinically or histologically.

We screened cases at our institution over a 6-month period and found 28 such lesions. Lesions were most often found on the trunk as a solitary papule, for which the clinical diagnosis was often basal cell carcinoma. There was a slight female predominance.

Confluent acantholysis and dyskeratosis is a histologic pattern that may present as a solitary keratosis.
CLEAR CELL ACANTHOMA Also known as pale cell acanthoma. Firm brown to red dome shaped nodule occurring on the lower legs of middle-aged to elderly patients.

Histologically there is a well-demarcated area of psoriasiform hyperplasia with pallor of the keratinocytes. There may be scattered neutrophils within the epidermis.

J Am Acad Deramtol 2001;44:2 (Letter to the Editor)

Polypoid clear cell acanthoma (CCA) with a diameter of 3 cm

A polypoid growth is unusual for this tumor and a polypoid CCA of this size has never before been reported in the literature

CLEAR CELL PAPULOSIS Multiple white papules on the trunk of young women. It may measure up to 1 cm and number more than 100. Histologically, there is mild acanthosis with pale cells scattered throughout the epidermis.
DERMATOSIS PAPULOSA NIGRA May be a variant of seborrheic keratosis. Almost always found on head and neck area in black females. Histologically resembles the reticulate variant of seborrheic keratosis.
EPIDERMOLYTIC ACANTHOMA May be solitary or disseminated resembling a wart. Histology shows epidermolytic hyperkeratosis.
LARGE CELL ACANTHOMA These are sharply demarcated scaly patches occurring in sun-exposed areas of middle-aged to elderly patients. Histologically, there is epidermal acanthosis with enlarged keratinocytes, often twice as large as normal.
MELANOACANTHOMA Pigmented nodule occurring on the trunk and head and neck of older patients. Histologically resembles a pigmented seborrheic keratosis.
Reticulated acanthoma with sebaceous differentiation.

Fukai K, Sowa J, Ishii M.

Department of Dermatology, Osaka City University Graduate School of Medicine, Osaka, Japan.

Am J Dermatopathol. 2006 Apr;28(2):158-61. Abstract quote  

Reticulated acanthoma with sebaceous differentiation (RASD) is characterized by the reticulated proliferation of spinous cells with aggregates of mature sebocytes in the bases of the strands of the keratinocytes, often linking rete ridges.

Here, we report the first case reported as RASD. A 55-year-old woman presented with a 15-year history of a slightly pruritic patch on the upper back, and the histology was typical for RASD. She had been bothered by a yellow discharge from the tumor. Skin tumors with sebaceous differentiation are occasionally associated with Muir-Torre syndrome. However, immunohistochemical staining for mutS homolog 2 (MSH-2) and mutL homolog 1 (MLH-1) showed positive staining within the nuclei of sebaceous cells and cells in the dermis.

Therefore, it is most likely that the present case is not associated with Muir-Torre syndrome.
WARTY DYSKERATOMA Usually solitary resembling a wart on the head and neck of middle-aged to elderly patients. Histology shows suprabasilar clefting, acantholysis, dyskeratosis, and keratinous plug.
Plaque form of warty dyskeratoma - acantholytic dyskeratotic acanthoma.

Department of Dermatology and Veneorology, Medical University of Łódź, Łódź, Poland.


J Cutan Pathol. 2007 Jun;34(6):494-6. Abstract quote

We report the case of a 64-year-old man with a plaque-like lesion on the lower back. Clinically, squamous cell carcinoma was suspected, but the histological features resembled those of isolated Darier's disease or pemphigus vegetans. The lesion was removed with the final diagnosis of acantholytic dyskeratotic acanthoma.

We discuss this case with special regard to the differential diagnosis of other isolated acantholytic acanthomas.

Warty dyskeratoma-"follicular dyskeratoma": Analysis of clinicopathologic features of a distinctive follicular adnexal neoplasm.

Kaddu S, Dong H, Mayer G, Kerl H, Cerroni L.

Department of Dermatology, University of Graz.

J Am Acad Dermatol 2002 Sep;47(3):423-8 Abstract quote

BACKGROUND: The clinicopathologic spectrum of warty dyskeratoma (WD) is not well characterized and the pathogenesis of this unusual lesion is still unclear.

OBJECTIVE: We reviewed the clinical and histopathologic spectrum of WD and investigated a possible involvement of human papillomavirus (HPV) infection in onset of this lesion.

METHODS: A total of 46 cases of WD were analyzed clinically and histopathologically. Polymerase chain reaction (PCR) analysis for HPV-DNA was performed in 13 lesions of WD.

RESULTS: A total of 46 lesions of WD from 45 patients (M/F ratio, 1:1.8; mean age 59.8 years, median 61 years, age range 3-88 years) presented as solitary papules or small nodules on the head and neck (32 cases), trunk (9 cases), lower extremities (4 cases), and upper extremities (1 case). One patient had 2 lesions. No patient had clinical signs of Darier's or Grover's disease. Histopathologically on scanning magnification, lesions showed mainly 3 architectural patterns, namely, cup-shaped (29 cases), cystic (6 cases), and nodular (2 cases). In 9 cases, a combination of two of these morphologic patterns was observed. Characteristically, the epithelial component in all WDs displayed foci of acantholytic dyskeratosis. Variable features suggestive of follicular differentiation toward the infundibular portion of a normal hair follicle were also observed, including a focal contiguity to pilosebaceous units in most cases (63%), and the presence of small infundibular cystic structures in a subset of lesions (46%). The majority of lesions (83%) also revealed a hyalinized or fibrous stroma with intrastromal clefts. PCR analysis for HPV-DNA performed in 13 cases inclusive of all representative architectural patterns was negative.

CONCLUSION: We conclude that WD shows a wider spectrum of morphologic features than previously recognized. Despite some histopathologic similarities to viral warts, WD is not a manifestation of HPV infection. On the other hand, the majority of these lesions display overall histopathologic features consistent with a follicular adnexal neoplasm. On the basis of this finding, we propose the alternative term follicular dyskeratoma to better reflect the distinctive features of this peculiar lesion.

Macpherson and Pincus. Clinical Diagnosis and Management by Laboratory Methods. Twentyfirst Edition. WB Saunders. 2006.
Rosai J. Ackerman's Surgical Pathology. Ninth Edition. Mosby 2004.
Sternberg S. Diagnostic Surgical Pathology. Fourth Edition. Lipincott Williams and Wilkins 2004.
Robbins Pathologic Basis of Disease. Seventh Edition. WB Saunders 2005.
DeMay RM. The Art and Science of Cytopathology. Volume 1 and 2. ASCP Press. 1996.
Weedon D. Weedon's Skin Pathology Second Edition. Churchill Livingstone. 2002
Fitzpatrick's Dermatology in General Medicine. 6th Edition. McGraw-Hill. 2003.
Weiss SW and Goldblum JR. Enzinger and Weiss's Soft Tissue Tumors. Fifth Edition. Mosby Elesevier 2008

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Last Updated March 12, 2008

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