Misdiagnosed follicular adenoma with 11 year postoperative liver and lung metastases a case report and literature review

As the second most common thyroid cancer, the follicular form has a good prognosis, but it is easily confused with follicular adenoma pre-operatively, which often leads to misdiagnosis, delayed treatment, and an increased risk of hematogenous metastasis. The optimization of diagnostic and treatment strategies is crucial for increasing the early diagnosis rate and improving the prognosis. A 73-year-old male was misdiagnosed as "follicular adenoma" 11 years previously and the left thyroid adenoma was resected. He was admitted with a confirmed diagnosis of follicular thyroid cancer and multiple metastases to the liver and lungs. A total resection of the left residual thyroid and the right thyroid and isthmus was performed, combined with bilateral central lymph node dissection, and post-operatively, two 131I-NaI 100 mCi treatments for the metastatic foci in the liver and lungs were administered, as well as regularly receiving oral levothyroxine replacement therapy. The one-year follow-up showed no recurrence of the primary foci and a significant reduction in metastatic foci, confirming the effectiveness of the comprehensive treatment program. Pre-surgery, follicular thyroid carcinoma is easily confused with follicular adenoma and nodular goiter with non-invasive encapsulated follicular tumors with papillary carcinoma nuclei, and it requires standardized treatment and detection of metastatic foci. Surgery combined with radioiodine is the mainstay of treatment and it is supplemented with levothyroxine replacement therapy. Targeted drugs are available for patients, refractory to radiotherapy. Long-term follow-up is essential to improve the prognosis.