Linear porokeratosis (LP) is an uncommon form of porokeratosis that is typically congenital, though lesions may arise in adulthood. LP’s follow Blaschko lines and are most often unilateral; however, they can rarely be generalized.3 Of all variants of porokeratosis, LP carries the highest risk for malignant transformation, estimated to occur in up to 19% of cases.11Our patient’s lesion was clinically consistent with LP, which was confirmed histologically. She had multiple risk factors for malignant transformation including a large, long-standing lesion, and location on the extremity.3-4 Other known risk factors for malignant transformation include sun exposure, immunosuppression, and ionizing radiation.1,2,4,5 While there are a few cases in the literature of multiple squamous cell carcinomas arising within linear porokeratosis, to our knowledge this is the first case to present with recurrence of a malignancy treated six years prior. This case highlights the importance of regular monitoring and surveillance for malignant degeneration in patients with large and long-standing linear porokeratosis.
1. Sasson, M, Krain, A. Porokeratosis and cutaneous malignancy: a review. Dermatol Surg. 1996;22:339-42.
2. Maubec E, Duvilard P, Margulis A. Common skin cancers in porokeratosis. Br J Dermatol. 2005;152:1389–91.
3. Sertznig P, von Felbert V, Megahed M. Porokeratosis: present concepts. JEADV. 2012;26:404-412.
4. Otsuka F, Umebayashi Y, Watanabe S, Kawashima M, et al.Porokeratosis large skin lesions are susceptible to skin cancer development: histological and cytological explanation for the susceptibility. J Cancer Res Clin Oncol. 1993;119:295–400.
5. Bencini PL, Tarantino A, Grimalt R, Ponticelli C, et al. Porokeratosis and immunosuppression. Br J Dermatol. 1995;132:74–8.