Abstract
Immunotherapy is standard care for stage III and IV melanoma. In the neoadjuvant setting, the histopathologic response ranges from focal fibrosis to sheet-like tumoral melanosis. In some cases, this pathologic response may mimic disease progression clinically. Herein, we report three cases of pathological response following neoadjuvant immunotherapy in patients with metastatic melanoma. All patients had an initial diagnosis of stage III to IV metastatic melanoma and received immunotherapy with pembrolizumab, ipilimumab, nivolumab, and/or talimogene laherparepvec. They presented to our institution with worsening blue plaques and/or swelling near the primary melanoma site, clinically concerning for microsatellites or in-transit melanoma metastasis. Histological examination demonstrated complete pathologic response to immunotherapy in two cases. One patient showed superficial dermal melanophages and chronic inflammation, while another patient showed tumoral melanosis and necrosis. Immunohistochemical stain to Melan-A was negative, confirming the absence of residual melanoma. The third case demonstrated clinical worsening of lesions and histopathologically had partial response characterized by persistent melanoma with variable tumoral melanosis. In conclusion, our cases raise awareness that partial and complete response to immunotherapy can clinically mimic disease progression. Additionally, these cases reinforce the spectrum of histopathologic response patterns to immunotherapy.
Financial Disclosure:
No current or relevant financial relationships exist.