Solid-pseudopapillary tumor with an elderly woman, showing an increase in size over a four-year follow-up period: report of a case]

Solid-pseudopapillary tumor (SPT) is considered to be a tumor showing an essentially benign biological behavior based on the results of histological examination of resected specimens and postsurgical follow-up. Little is known regarding the growing speed and pattern, and the process of cystic structure formation of this tumor due to a lack of reports describing its natural history. We herein report a case of SPT showing an increase in size in a four-year follow-up period, which underwent resection thereafter.