PSAT285 A Rare Case of Co-Existing Papillary Thyroid Cancer with Lung Metastasis and Lung Adenocarcinoma

INTRODUCTION: Multiple primary tumors are defined as the presence of two primary tumors of different histologies in the same individual, which can be diagnosed at the same time or at different times. We present a rare case of papillary thyroid cancer (PTC) with pulmonary metastasis and lung adenocarcinoma diagnosed simultaneously and highlight the importance of identifying multiple primary cancers to guide management and improve patient outcomes. CLINICAL CASE: A 57-year-old female with no prior history of malignancy was found to have a 12 mm left upper lobe lung nodule on CT chest as a part of evaluation of worsening cough. A fluorodeoxyglucose PET scan showed increased uptake in the left upper lobe nodule as well as a hypermetabolic thyroid nodule in the right thyroid lobe. She underwent a thoracoscopy, wedge resection, and left lung lobectomy with lymph node dissection, and pathology revealed adenocarcinoma of the lung as well as incidentally found PTC. Subsequently, thyroid ultrasound was obtained which showed a right upper mid-pole thyroid nodule measuring 1.7 cm. She underwent a total thyroidectomy, and pathology showed PTC, tall cell variant in the right lobe, with largest tumor dimension 1.5 cm with no extrathyroidal extension, no lymphatic, and no vascular invasion. A nuclear uptake scan post thyroidectomy showed focal uptake in the thyroid corresponding to residual thyroid tissue, without evidence of metastatic disease. She subsequently received 152.6 mCi of radioactive iodine (RAI). A post-therapy scan obtained one week later showed no new uptake. After RAI, her thyroglobulin antibody remained negative and thyroglobulin became undetectable. She remains on levothyroxine therapy with her TSH at target of 0.1-0.4 U/L. However, she unfortunately had recurrent disease of her lung adenocarcinoma and is continuing to undergo treatment with chemotherapy CONCLUSION: PTC is the most common type of differentiated thyroid cancer and generally has a better prognosis than other types of thyroid cancer given its indolent course. Histologic subtype, presence of extra thyroidal extension, lymph node involvement, and distant metastasis play a role in prognosis, and PTC metastasizes to the lungs in about 5% of cases. Clinicians should be aware of the possibility of multiple primary tumors, and the use of diagnostic modalities like FDG-PET and tissue biopsy can help differentiate a second primary tumor from metastatic disease. Radioactive iodine therapy (RAI) for management of differentiated thyroid carcinoma has been linked to predisposition to other primary malignancies such as leukemia and lymphoma, however our patient was found to have both malignancies simultaneously prior to receiving RAI. This suggests the possibility of genetic susceptibility or alterations in the immune constituency. Further studies are needed to analyze the genetic and environmental factors that lead to development of two primary tumors in certain individuals. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.