Metastatic Papillary thyroid carcinoma

My husband has been diagnosed with metastasis papillary thyroid carcinoma in October 2023. He has undergone thyroidectomy and neck dissection (8 hour surgery!). 20 out of 30 lymph nodes were cancerous. He has had 1 treatment of R-131. His thyroglobin has been consistent and never elevated. So, clearly this is NOT a good indicator if cancer has came back. Finally just got the doctors to come to this realization after 6 months! He has had a CT and PET Scan in April.....claims no cancer only in the neck. However, he is so sick!!! Extremely exhausted, nausea, can't eat, losing weight, short term memory loss, etc. No one will listen!!! We finally got through this week, he had a gastrointestinal appointment along with neurology. He recently found a lump in his armpit. He got an ultrasound yesterday. It is described as well-defined,
heterogeneous ovoid solid mass. The radiologist claims it may be lipoma.Given his history, shouldn't it be checked out further??? It is growing at a rapid rate! How can anyone to listen before it has spread more???? Anyone with advice. Please help!