BACKGROUND Intimal sarcoma (IS) is a malignant mesenchymal tumor with predominantly intraluminal growth in large vessels and the heart. Due to the rarity of cases it often poses diagnostic problems in clinical and pathological settings. Although the classification of IS is still controversial, undifferentiated type of IS has recently been found to show immunohistochemical positivity with MDM2, CDK4, or PDGFRA and amplification of MDM2/CDK4 and PDGFRA. CASE REPORT The patient was a 76 years-old Japanese man who presented with superior vena cava (SVC) syndrome. CT identified a tumor or thrombi in the SVC, bilateral brachiocephalic, and jugular veins. The histology of the biopsy specimen revealed an undifferentiated tumor without immunohistochemical positivity for all antibodies available except vimentin and smooth muscle actin. He was treated conservatively and died of respiratory failure 2 months after presentation. At autopsy, the large veins were filled by a sausage-like tumor and the cut sections revealed hemorrhagic and necrotic tumor. The tumor cells were negative with MDM2, CDK4, and PDGFRA by immunohistochemistry. Amplification of MDM2 and PDGFRA was not identified by fluorescence in-situ hybridization. CONCLUSIONS We concluded that the case was an undifferentiated sarcoma (IS without any specific phenotype) arising in the SVC, bilateral brachiocephalic, and jugular veins. We propose a way of subtyping sarcomas with predominantly intraluminal growth in large vessels and the heart based on immunohistochemistry and amplification of MDM2 and PDGFRA. However, proper subtyping of these sarcomas requires further study.
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