Papillary Endothelial Hyperplasia (Masson Tumor) Mimicking Metastasis in a Patient with a History of Diffuse Large B-Cell Lymphoma: A Rare Case of Sacral Involvement

Papillary endothelial hyperplasia, also known as Masson tumor, is an uncommon benign vascular proliferation that may clinically and radiologically resemble malignancy. This report presents a 46-year-old female patient with a prior history of stage IV diffuse large B-cell lymphoma in remission who presented with chronic low back pain. Imaging revealed a suspicious lesion in the S1 vertebral corpus, raising concern for possible spinal metastasis. Surgical intervention revealed an intensely hemorrhagic lesion without a defined mass, and histopathological analysis confirmed the diagnosis of Masson tumor. This case emphasizes the importance of considering benign vascular etiologist such as Masson tumor in diagnosing spinal lesions in oncology patients. It highlights the role of histopathology in avoiding misdiagnosis and unnecessary treatment.