Hello Joyce,
In general, an enlarged spleen is always a concern unless it is a known congenital normal variant or there is a known preexisting medical condition which commensurate with the size of the enlarged spleen.
A person's spleen can enlarge as a result of pressure build-up such as the case of liver cirrhosis or occlusion of the splenic venous outlet. Either of these conditions require further work-up. Other causes of an enlarge spleen include chronic infections, metabolic abnormalities, bone marrow disease, lymphoma and other blood related diseases.
The investigations for an enlarged spleen may include scans, special blood tests and bone marrow examination or biopsy. Whether any treatment is required or available will depend on the final diagnosis. Hope that helps.
-Dr Quan