<s>[INST] Hi Doctor. I just got back from my CT scan. 3 months ago they located a 2 cm mediastynum cyst on the right side of my chest. My doctor sent me to get another CT 3 months later to see if it grew. Thy told me that it looks the same and that it is on the right side of my body near my heart. What should I do? And what is it? [/INST] Respected user, hi I evaluated your query thoroughly .* Mediastinal cyst has vivid pathologies ranging from benign neuronal tumors   to malignant ones .* Mediastinal cyst evaluation needs correlation with detailed history of the    patient , clinical assessment , signs elicited by the consultant, exact location    in the mediastinum with in depth analysis of reports , Biopsy of the lesion   giving histopathological evidence of the disease.Hope this helps you.Welcome for any further queries.Thanks for using Healthcaremagic.com & giving me an opportunity to assist you.Wishing you healthy life ahead.Regards dear take care. </s>