A man in his 80s presented with a 2-year history of an asymptomatic, expanding eruption on the trunk and extremities. He denied any systemic symptoms. Physical examination revealed a serpiginous, erythematous eruption with a peripheral scale resembling wood grain (Figure). Histologic findings showed a perivascular lymphohistiocytic infiltrate with no deposition noted on a direct immunofluorescence assay. A workup for malignancy revealed a mass in the prostate with bilateral para-aortic and inguinal lymphadenopathy and an elevated level of prostate-specific antigen. The patient declined surgery and was lost to follow-up.Erythema gyratum repens (EGR) is a rare type of figurate erythema first described by John Gammel, MD, in 1952. 1 The rash has a characteristic appearance with erythematous concentric and parallel bands (wood grain pattern) and a collarette of scale. The typical distribution involves the trunk and proximal extremities but spares the hands, feet, and face. 2 Advancement of the rash is usually rapid. The mean age at diagnosis is in the seventh decade of life, with a 2:1 male-to-female ratio. 2 In approximately 70% of cases, EGR is considered a paraneoplastic condition. 2 Although in most patients the eruption precedes the diagnosis of an underlying neoplasm by several months, the rash may also present in those with an established malignant tumor. 3 The most commonly associated types of neoplasms are lung, esophageal, and breast cancer. 2 Figurate erythemas should be carefully considered in the differential diagnosis, as should other conditions that may present with EGR-like morphologic features, including resolving pityriasis rubra pilaris, ichthyosis, syphilis, lupus erythematosus, autoimmune blistering diseases, neutrophilic dermatoses, and cutaneous T-cell lymphoma.In EGR, histologic examination results are not specific and may reveal parakeratosis, spongiosis, and a perivascular lymphohistiocytic infiltrate in the papillary dermis. Deposits of immunoglobulin G, C3, and C4 may be observed in the basement membrane on an immunofluorescence assay. The exact pathogenesis of paraneo-plastic EGR is still debated, but an immune response triggered by the malignant neoplasm is suspected. 4 Given the high risk of paraneoplastic disease, cancer screening is strongly recommended. Patients should ensure that their routine cancer screening tests are updated and that appropriate symptoms are evaluated. If results of such studies are normal, thoracic imaging with chest radiography and computed tomography should be considered because of the association between EGR and thoracic malignant tumors. Patients should be advised to remain current with future cancer screening tests if no malignant neoplasm is detected.Neither immunosuppressive therapy nor retinoid treatment is effective against EGR. Resolution requires successful treatment of the underlying disease. 3