Porokeratome

Walsh, 2007

Rare benign neoplasm first described in 2007 by Walsh SN et al (< 20 cases known to date), presenting as a 1.0-2.0 cm, usually solitary, scaly brown to gray-brown, asymptomatic, broad-based, firm nodule. Advanced lesions present as sharply demarcated, irregular verrucous nodules; sometimes with sunken center and accentuated annular horny ridge. Clinically, the findings are indistinguishable from a "classic keratoacanthoma" (Batalla A et al. 2013).

Patients of middle to higher age - 50-70 years. Less often younger.

Located primarily on the distal extremities. Also described is the occurrence in the facial area, on the chest and buttocks.

Histologically, there is a benign acanthoma with compact orthokeratosis; focally distinct parakeratotic cornoid lamellae with absence of stratum granulosum, superficial lymphohistiocytic inflammatory infiltrate in the corium. In isolated cases, PCR sequencing and in situ hybridization demonstrated the presence of human papillomavirus (HPV) type 16. (Kanitakis J et al. 2009; Caseiro Silverio P et al. 2015).

• Verruca vulgaris
• Keratoacanthoma
• Squamous cell carcinoma

Excision for histological confirmation of the diagnosis (which should generally be a random diagnosis) is useful.

No association with immunosuppression to date. No reports of a tendency to malignant transformation

1. Batalla A et al (2013) Porokeratoma: a different entity or a variant of verrucous (hyperkeratotic) porokeratosis? Indian J Dermatol 58:158.
2. Caseiro Silverio P et al (2015) Porokeratoma: A Possible Association with Human Papillomavirus Infection. Dermatopathology (Basel) 2:43-45. illustration histo.
3. Kanitakis J et al (2009) Porokeratoma (porokeratotic acanthoma): immunohistological study of a new case. J Cutan Pathol 36:804-807.
4. Tan, Cheng (2015) Porokeratotic acanthoma- JDDG 13: 151-153.
5. Wade TR et al.(1980) Cornoid lamellation. A histologic reaction pattern. Am J Dermatopathol 2:5-15.
6. Walsh SN et al (2007) Porokeratoma. Am J Surg Pathol 31:1897-1901. -
7. Weedon D. Weedon's Skin Pathology. 3rd London: Churchill Livingstone Elsevier; 2010.

8. Zhang Z et al. (2016) Genomic variations of the mevalonate pathway in porokeratosis. eLife 4: e06322, 2015.