LAUSR

Keratoacanthomas (KA) may arise in tattoos. Although the pathogenesis remains unclear, it has been postulated that there may be a hypersensitivity reaction to the tattooing process or the ink itself may possess carcinogenic qualities. We present two cases of eruptive KAs occurring in tattoos within 2 weeks of the tattooing process. Case one was a 57-year-old Caucasian man who presented with eight keratotic nodules 2 weeks after receiving a red-blue-black-green tattoo of a fish on his left forearm (Fig. 1). His general practitioner performed two 3-mm punch biopsies on two lesions, which were both initially reported as well-differentiated squamous cell carcinoma (SCC). Clinically the lesions were consistent with eruptive KAs. An expert dermatopathologist reviewed the biopsies, favouring KA over SCC. Acitretin was commenced at a dose of 10 mg daily, which was titrated to 30 mg daily over 8 weeks. All keratotic lesions within the tattoo resolved over 5 months of treatment and the patient was then slowly weaned off acitretin over 3 months. A solitary lesion persisted above the tattoo, which was excised, the histopathology of which was consistent with KA. The patient has remained free of recurrence and free of new primaries at 10 months of follow up. Case two was a 38-year-old Aboriginal woman who presented with six painful eruptive nodules in an orange-redblack-green tattoo of a flower camouflaging a pre-existing black tattoo (Fig. 2). These nodules appeared within 2 weeks of receiving the new tattoo. The general practitioner performed a single 3-mm punch biopsy, which was initially reported as a well-differentiated SCC. Clinically the lesions were consistent with eruptive KAs, however, given the initial histological diagnosis of SCC, the patient opted for excision of the previously biopsied lesion (necrotic lesion left of photo). An expert dermatopathologist reviewed both the punch and excisional biopsy and favoured KA over SCC. The patient, who had undergone a previous tubal ligation, was then commenced on acitretin at a dose of 10 mg daily, which was titrated to 30 mg over 4 months. Intralesional 0.5 mL of triamcinolone acetonide of 10 mg/mL was also injected to the most indurated areas around the nodules to control pruritus. The patient has remained free of recurrence and free of new primaries at 9 months of follow up; however, on lowering acitretin, the area becomes thickened and pruritic. KA has a distinctive crateriform architecture, with a proliferation of mildly atypical squamous cells around the base of the crater. The distinction between KA and well-differentiated SCC may not be possible on histological grounds alone. This may even be more difficult in punch biopsy specimens, as the crateriform architecture may not be fully appreciated when only a portion of the lesion is present. Where there is difficulty distinguishing KA from SCC an expert dermatopathology opinion may be helpful.