Track: Case Reports

Topic: Melanocytic Neoplasms

Abstract:

Pembrolizumab (Keytruda), used since 2014 for treating metastatic melanoma, can cure melanoma by unleashing T cell cytotoxic activity that is inhibited by the PD-1/PD-L1 pathway, inducing tumor regression. The standard course involves one dose every three weeks for up to 2 years, resulting in a 30–40% complete clinical response. We report an unexpected complete response of metastatic melanoma after a single dose of pembrolizumab. Our patient is a 60-year-old male with a mixed spindle cell and desmoplastic melanoma of the right upper back (10mm Breslow thickness, nonulcerated) who was found to have metastatic melanoma (Stage IIIC, pT4aN1M0) of the right supraclavicular lymph node, as confirmed by pre-operative radiologic and pathologic assessments. Following the administration of one dose of pembrolizumab, the treatment was discontinued due to immunotherapy-related pneumonitis. Re-staging PET/CT at four months demonstrated complete resolution of the right supraclavicular lymph node with no other FDG avid lesions identified. The patient underwent a targeted lymph node biopsy of the right supraclavicular lymph node. Histopathologic examination demonstrated a sclerotic lymph node, and immunohistochemistry failed to demonstrate evidence of melanoma. To the best of our knowledge, this is the first documented instance of complete remission of metastatic melanoma following one single dose of pembrolizumab treatment.

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Thuy B Tran, M.D.