Late development of splenic sarcoidosis-like lesions in a patient with metastatic melanoma and long-lasting clinical response to ipilimumab

A male patient with Stage IV melanoma was treated with ipilimumab resulting in a long-lasting partial response according to RECIST criteria. However, twenty months after ipilimumab treatment, routine follow-up CT scan revealed new splenic lesions initially interpreted as indicative of progressive disease. Nevertheless, a biopsy was performed and histologic evaluation showed that the lesions did not contain malignant cells but rather constituted non-caseating epithelioid cell granulomas consistent with sarcoidosis. As the patient was asymptomatic no treatment was initiated and over the following months the splenic lesions slowly disappeared and to date the patient remains in remission. Ipilimumab is now widely used in the treatment of melanoma patients. Our case-report illustrates that physicians should consider the possibility of ipilimumab induced visceral sarcoidosis-like reactions, mimicking metastatic lesions, developing even many months after ipilimumab treatment. Thus, biopsy of such suspicious lesions is advisable to avoid misinterpretation as disease progression and unnecessary resumption of cancer therapy.