<s>[INST] I am 52 years old, male, active in sports. I got sick couple days back, fever, I went to my doctor for a check-up. Had an x-ray done as well. Results show that I have a well-defined ovoid opacity in the left lower lung overlying the 6th anterior and 9th posterior ribs. Is this ok? Is this life threatening? Thank You.. [/INST] Thanks for your question on Chat Doctor. There are many causes for ovoid opacity in left lower lung. Like1. Benign cystic lesion (oncogenic cyst)2. Malignant mass3. Rounded pneumonia etc. So we need to rule out all these. CT thorax with contrast is needed in your case. As CT will give you better idea about the lesion like exact size of the lesion, its shape, borders, necrotic or not, associated with lung lesion or not, mediastinal lymph nodes enlarged or not etc. And all the above points are important in deciding etiology. And you may need biopsy also for proper diagnosis. </s>