Case Reports

Metastatic Melanoma Mimicking Eruptive Keratoacanthomas

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Depending on the subtype of cutaneous metastases (eg, satellitosis, in-transit disease, distant cutaneous metastases), the location prevalence of the primary melanoma varies. In a study of 4865 melanoma patients who were diagnosed and followed prospectively over a 30-year period, skin metastases were mostly locoregional and presentation on the leg and foot were disproportionate.1 In contrast, the trunk was overrepresented for distant metastases. Distant metastases also were more associated with concurrent metastases to the viscera.1 Accordingly, a patient’s prognosis and management will differ depending on the subtype of cutaneous metastases.

Eruptive or multiple KAs classically have been associated with the Grzybowski variant, the Ferguson-Smith familial variant, and Muir-Torre syndrome. It was reported as a paraneoplastic syndrome associated with colon cancer, ovarian cancer, and once with myelodysplastic syndrome.3 Keratoacanthomas are being classified as well-differentiated squamous cell carcinomas and have metastatic potential. A biopsy is recommended to diagnose KAs as opposed to historically being monitored for resolution. A skin biopsy is the standard of care in management of KAs.

In addition to being associated with Muir-Torre syndrome and classified as a paraneoplastic syndrome,3 eruptive KAs can occur following skin resurfacing for actinic damage, fractional photothermolysis, cryotherapy, Jessner peels, and trichloroacetic acid peels.6 A couple other uncommon settings include a case report of an arc welder with job-associated radiation and multiple reports of tattoo-induced KAs.7,8 There is the new increasingly common association of squamous cell carcinomas with BRAF inhibitors, such as vemurafenib, for metastatic melanoma.9

In a 2012 review article on cutaneous metastases, Riahi and Cohen10 found 8 cases of cutaneous metastases presenting as KA-like lesions; none were metastatic melanoma. All were solitary lesions, not multiple lesions, as in our patient. The sources were lung (3 cases), breast, esophagus, chondrosarcoma, bronchial, and mesothelioma. The most common location was the upper lip. Additionally, similar to our patient, they behaved clinically as KAs with rapid growth and keratotic plugs and were asymptomatic.10

Metastatic melanoma may mimic many other cutaneous processes that may make the diagnosis more difficult. Our case indicates that cutaneous metastases may mimic KAs. Although multiple KA-like lesions can spontaneously occur, a paraneoplastic syndrome and other underlying etiologies should be considered.

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