Metastatic germ cell tumour presenting as acute megakaryoblastic leukaemia and disseminated melanoma: A case report

Abstract

Since first recognised in 1985, studies have described the unique and rare association between haematological malignancies and germ cell tumours, most commonly acute megakaryoblastic leukemia (AMKL) and non-seminomatous germ cell tumours. A recent molecular study identified mutations in PTEN and TP53 in both tumours, supporting the theory that distinct genomic alterations underlie this rare association. It is also recognised that teratomatous components of mediastinal germ cell tumours have a tendency for secondary transformation to other malignancies including melanoma. We report a case of a 38-year-old man presenting with severe back pain. An MRI spine demonstrated diffuse marrow replacement and bony lesions concerning for metastatic disease. The patient had recently completed chemotherapy for a mediastinal germ cell tumour with teratomatous components on histopathology. A staging CT identified liver and splenic lesions suspicious for metastatic deposits. A peripheral blood film performed on admission was found to have circulating blasts with an immunophenotype consistent with megakaryoblasts. He subsequently underwent a bone marrow biopsy confirming AMKL with a TP53 mutation. A liver biopsy revealed necrotic tumour with immunohistochemistry consistent with metastatic melanoma. In summary, we describe a case of treated mediastinal germ cell tumour with secondary transformation to metastatic melanoma with synchronous AMKL.