1.5 to 1.9cm, 2 lymph nodes neat suspected thymoma in ant mediastinum. pet suv was 3.8 for thymoma and 4.7 for 1.9 node. could it it by lymphoma?

Maybe: There are typical appearances of certain cancers but none are specific enough to provide a diagnosis. What you describe sounds worrisome for a malignant thymoma or thymic carcinoma with metastases to lymph nodes. Could it be lymphoma? Yes. Could it be lung cancer metastatic to nodes and thymoma? Yes. A biopsy is needed to make the correct diagnosis. Case presentation at a tumor board is best.

Hard to tell, Biopsy: Only a biopsy can tell the cause of these abnormalities. Unless you have some symptoms from these lesions in the mediastinum, i would be inclined to wait before jumping right now into this area for a biopsy. An interval repeat study pet or ct scan in 2 months would be my preference. Why were all these tests done? Do you have any pain or fever? What is your doctor's recommendation for further step.