Oncovirus es (viruses that can cause cancer) include human papillomavirus ( cervical cancer ), Epstein–Barr virus ( B-cell lymphoproliferative disease and nasopharyngeal carcinoma ), Kaposi's sarcoma herpesvirus ( Kaposi's sarcoma and primary effusion lymphomas), hepatitis B and hepatitis C viruses ( hepatocellular carcinoma ) and human T-cell leukemia virus-1 (T-cell leukemias). Bacterial infection may also increase the risk of cancer, as seen in Helicobacter pylori -induced gastric carcinoma .   Parasitic infections associated with cancer include Schistosoma haematobium ( squamous cell carcinoma of the bladder ) and the liver flukes , Opisthorchis viverrini and Clonorchis sinensis ( cholangiocarcinoma ). 
Primary skeletal tumors do not typically cause neurologic signs. Multilobular osteochondroma originates in the flat bones of the skull, usually in older medium- or large-breed dogs and appears as a firm, fixed mass. It may erode the cranium and compress, rather than infiltrate, underlying brain tissues. Radiographically, the tumor contains nodular or stippled areas of mineralization, resulting in a characteristic “popcorn ball” appearance. Local recurrence and metastasis are common. Vertebral osteochondroma is the spinal cord counterpart.