Parosteal Osteosarcoma with Pancreatic Metastasis and Multiple Relapses: A Case Report and Review of the Literature.

Osteosarcoma is the most common primary bone cancer in all age groups. Metastasis mostly occurs with high-grade tumors disseminating to the lungs and other bones. Spread to the pancreas is rare and undocumented in the low-grade subtypes. Additionally, it is uncommon for the disease course of low-grade subtypes to involve multiple relapses. We present a 35-year-old woman with parosteal osteosarcoma who has experienced an atypical metastasis to the pancreas as well as multiple local and pulmonary relapses. The lesion was identified incidentally on routine imaging, and the patient underwent resection. We compare our case to the other reports of pancreatic metastasis in the literature. Despite being especially rare, clinicians ought to be aware of pancreatic metastasis of osteosarcoma. Furthermore, despite parosteal osteosarcoma's less aggressive disease course, it can uncommonly lead to multiple relapses. We present a rare case exemplifying these phenomena in the prognostically favorable histologic subtype of parosteal osteosarcoma.