Abstract
Cutaneous paraneoplastic granulomatous eruption (CPGE) describes a malignancy-associated reactive granulomatous dermatitis. Previous reports of CPGE associated with chronic myelomonocytic leukemia (CMML) have presented as palisaded neutrophilic and granulomatous dermatitis (PNGD)-like eruptions. We describe a case of CPGE with an interstitial granulomatous dermatitis pattern. A 76-year-old man with CMML and non-small cell lung cancer status post resection presented with an asymptomatic rash on his chest and back for 1 to 2 years. Physical exam revealed dark red to violaceous infiltrated papules coalescing into a plaque on the central chest and ill-defined darkly erythematous to violaceous papules on the upper and lower back. Two prior biopsies were suggestive of granuloma annulare and dermatofibroma. The patient was undergoing surveillance but was not yet on treatment for CMML. A repeat skin biopsy revealed an interstitial and perivascular lymphohistiocytic infiltrate with aggregates of giant cells, consistent with an interstitial granulomatous dermatitis. Subsequent bone marrow biopsy was significant for a KRAS mutation, NRAS mutation, and TET2 mutation. His skin biopsy was positive for the same TET2 mutation, supporting a diagnosis of CPGE in association with his underlying CMML. Given his CMML is low risk, the patient is being monitored with routine blood work and computerized tomography scans of the chest for his history of lung cancer. His skin lesions remain asymptomatic and have minimally improved with topical corticosteroids.