Abstract
BACKGROUND: The coexistence of malignancies in a patient may be explained by the tumor-to-tumor metastasis phenomenon or multiple primary malignant tumors, both of which are not common findings. Here, we are going to present a case with coexistent papillary thyroid carcinoma and primary squamous cell carcinoma of the lung. CASE PRESENTATION: A 36-year-old Iranian man presented to our clinic for evaluation of constitutional symptoms. His past medical history was significant for papillary thyroid carcinoma due to which he had undergone total thyroidectomy, cervical lymph node dissection, and radioactive iodine therapy 14 years ago. Six months prior to admission, he received radioactive iodine therapy due to the metastatic involvement of both lungs with papillary thyroid carcinoma in another center with consequent improvement in symptoms. Diffuse nodular lesions in both lungs, a lesion in the lower lobe of his left lung, not present 6 months ago, peritoneal carcinomatosis, and several para-aortic lymphadenopathies were detected by imaging studies. A radioactive iodine uptake scan, positron emission tomography/computed tomography scan, and transbronchial biopsy of the lesion in the lung revealed concurrent squamous cell carcinoma of the lung and pulmonary metastasis of papillary thyroid carcinoma. After consultation with an oncologist, our patient received 6 months of chemotherapy; however, he died 8 months after presentation. CONCLUSIONS: Physicians should be aware of the possibility of the emergence of primary malignancies in patients with a history of papillary thyroid carcinoma, especially lung cancer as it is a common site of papillary thyroid carcinoma metastases. Using appropriate diagnostic evaluations in order to choose the best therapeutic option is of utmost importance.