Is a tumor on my normal size spleen anything to be worries about? any additional tests recommended?

Be more exact: We need complete information about your Spleen and the tumor. Send us the exact information from the Tests done which showed this tumor. Was it a CT scan that shows this tumor? The radiologist can indicate whether it is likely to be benign(?cystic) or potentially cancerous (size matters here). A properly done CT scan or MRI can answer your questions. Ask your doctor about all of above.