Abstract

Combination BRAF and MEK-inhibitor therapy is a mainstay of treatment in metastatic melanoma patients with BRAF V600E or V600K mutations. Dabrafenib and trametinib as single agents have shown improved survival outcomes, and in combination, there is less toxicity and delayed treatment resistance. We present a case of a 57-year-old male with stage IIIB melanoma, who had been on dabrafenib and trametinib combination therapy for four years. Recent PET scan showed multiple new hypermetabolic subcutaneous nodules on bilateral lower extremities. Patient had noticed these lesions on his lower legs over the last several months.There was concern for possible new metastases, and the patient presented to the WVU Dermatology for further evaluation and biopsy. A punch biopsy was performed, and histopathologic evaluation demonstrated a lobular and septal panniculitis with admixed foamy histiocytes, eosinophils, neutrophils, and granuloma formation. Tissue cultures were collected, which showed no growth of bacteria or fungus. This panniculitis was likely secondary to targeted melanoma treatment. Panniculitis is considered a rare side effect of combination dabrafenib/trametinib therapy. It is important to be aware of this entity as these lesions could be confused with new metastases and thus progressive disease. Learning from these cases can help to better characterize which patients get this side effect, when it occurs, and what ramifications it may have. Targeted melanoma treatments have various potential cutaneous adverse events. Awareness of these side effects is key for correct diagnosis and can help us to elucidate how these cutaneous adverse effects may reflect on treatment response and patient prognosis. Recognition of this effect can also help us to further elucidate subsequent complications and assess if cessation of treatment is warranted in these patients.

Financial Disclosure:
No current or relevant financial relationships exist.