Are You Confident of the Diagnosis?
What you should be alert for in the history
Stucco keratosis is a benign epithelial skin tumor. The lesion typically presents as a white or white-gray papule with a diameter of only a few millimeters (Figure 1, Figure 2). Stucco keratoses usually occur at a high number (often more than 100) on the extensor surfaces of the lower legs or forearms and the dorsal aspects of the hands and feet of elderly patients. Stucco keratoses show a ’stuck-on’ appearance to the skin and can be scraped off easily without bleeding.
Characteristic findings on physical examination
In most cases the diagnosis can be made according to the characteristic clinical features. Single lesions may be mixed up with viral warts (which may show evidence of autoinnoculation), acrokeratosis verruciformis (frequently on the dorsal hands and may be associated with Darier disease), hyperkeratosis lenticularis perstans (presents in a more generalized distribution) or epidermodysplasia verruciformis (lesions may resemble tinea versicolor and have a risk for the development of squamous cell carcinoma).
Expected results of diagnostic studies
In doubtful cases, histological examination is helpful. Stucco keratosis histologically resembles a hyperkeratotic seborrheic keratosis, showing orthohyperkeratosis and a church-spire like epidermal papillomatosis (’saw-tooth pattern’). Horn cysts are absent.
Who is at Risk for Developing this Disease?
Stucco keratosis mainly affect people aged 40 or older. The prevalence among men is reported to be four times higher than in women, and Caucasian patients are preferentially affected. The prevalence has been estimated between 7-20%, but in fact may be lower.
What is the Cause of the Disease?
The risk factors for this disease are not known, although the distribution of the affected body sites suggests a possible role of UV light. However, the face is usually not affected. It is assumed that this lesion represents a variant of (hyperkeratotic) seborrheic keratosis. The homologous histopathology between stucco keratosis and hyperkeratotic seborrheic keratosis supports this assumption. Furthermore, the detection of PIK3CA mutations in stucco keratosis is compatible with this hypothesis, because these mutations have been also found in seborrheic keratoses.
Systemic Implications and Complications
–Medical – imiquimod, keratolytics (6% salicylic acid, 12% ammonium lactate)
–Destructive – electrodessication, cryosurgery
–Surgical excision – curettage
Optimal Therapeutic Approach for this Disease
Stucco keratoses are benign skin lesions lacking a malignant potential. Therefore, treatment is not mandatory. Stucco keratoses can be removed by curettage or shave excision. A topical therapy with imiquimod has been reported.
Patient reassurance that these lesions are benign and are of no significance other than cosmetic appearance is essential. Treatment is only necessary should the patient desire it or, in the rare occasion, when lesions become irritated.
Unusual Clinical Scenarios to Consider in Patient Management
What is the Evidence?
Braun-Falco, O, Weissmann, I. “Stuccokeratoses. Review and own observations”. Hautarzt. vol. 29. 1978. pp. 573-7. (An older review on stucco keratosis with clinical remarks.)
Hafner, C, Landthaler, M, Mentzel, T, Vogt, T. “FGFR3 and PIK3CA mutations in stucco keratosis and dermatosis papulosa nigra”. Br J Dermatol. vol. 162. 2010. pp. 508-12. (This study detected PIK3CA mutations in stucco keratoses. These mutations are also found in (hyperkeratotic) seborrheic keratoses. The findings suggest a relationship between stucco keratosis and seborrheic keratoses.)
Hafner, C, Toll, A, Fernandez-Casado, A, Earl, J, Marques, M. “Acquadro F et al. Multiple oncogenic mutations and clonal relationship in spatially distinct benign human epidermal tumors”. Proc Natl Acad Sci U S A. vol. 107. 2010. pp. 20780-5. (This study shows that multiple oncogenic mutations (FGFR3, PIK3CA, RAS) are present in benign seborrheic keratoses, although these lesions lack a malignant potential.)
Stockfleth, E, Rowert, J, Arndt, R, Christophers, E, Meyer, T. “Detection of human papillomavirus and response to topical 5% imiquimod in a case of stucco keratosis”. Br J Dermatol. vol. 143. 2000. pp. 846-50. (This study reports successful treatment of stucco keratosis with topical imiquimod. However, it remains uncertain whether the detection of HPV in these lesions is really pathogenetically relevant or, more likely, represents a coincidental finding.)
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