Synchronous Development of Acute Megakaryoblastic Leukaemia and Disseminated Melanoma following Treatment of a Germ Cell Tumour: A Case Report

Somatic malignant transformation of germ cell tumours is a well-described but poorly understood phenomenon. It is characterized by differentiation of pluripotent teratoma cells into somatic tumour cells. Following malignant transformation, the most common histologies are sarcomas and primitive neuroectodermal tumours; however, other subtypes have been recognized including melanoma, leukaemia, and renal cell carcinoma. We report a case of a 38-year-old male who had recently completed treatment for a mediastinal germ cell tumour with teratomatous components. He presented several months after completion of chemotherapy with metastatic lesions in his spine and liver accompanied with severe pancytopenia. He was subsequently diagnosed with acute megakaryoblastic leukaemia (AMKL), and a biopsy of a liver lesion was consistent with metastatic melanoma. This case illustrates the simultaneous development of 2 rare malignant entities: mediastinal germ cell tumour-associated AMKL and somatic malignant transformation to melanoma. It also highlights the importance of close surveillance to detect these metastatic sequelae and the emerging role of tumour sequencing to establish targetable pathways.

Pathological and immunohistochemical aspects of acute megakaryoblastic leukaemia in a cat – Short communication

An adult, mixed-breed, feline leukaemia virus (FeLV-) positive female cat was presented with mucosal jaundice and a history of anorexia and constipation for three days. Physical examination revealed splenomegaly, cachexia, and dehydration. Humane euthanasia was conducted, followed by postmortem examination. Grossly, the cat was icteric, and presented hepatomegaly with multifocal white spots and splenomegaly. Histologically, the bone marrow was nearly completely replaced by a proliferation of megakaryocytes and megakaryoblasts, and there was a proliferation of fibrous connective tissue. Similar neoplastic proliferation was observed infiltrating the liver, lymph nodes, spleen, kidney, skeletal muscle, and lungs. Immunohistochemistry was performed for von Willebrand Factor (VWF), CD79α, CD3, feline immunodeficiency virus, FeLV, and CD61. Marked cytoplasmic labelling was observed in the neoplastic cells for FeLV, VWF and CD61, corroborating the diagnosis of acute megakaryoblastic leukaemia.