Simultaneous occurrence of papillary thyroid carcinoma, medullary thyroid carcinoma, and lymphoma: A case report.

[BACKGROUND] Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer, the coexistence of PTC and medullary thyroid carcinoma (MTC) is uncommon. While the simultaneous occurrence of both cancers with small lymphocytic lymphoma (SLL) in lymph nodes with PTC metastasis is very rare. This study presents a unique case of concurrent PTC, MTC, and SLL, highlighting the exceptional rarity of these coexisting tumors.

[METHODS] A 75-year-old female with a thyroid tumor underwent total thyroidectomy, bilateral central neck lymph node dissection, and right radical neck lymph node dissection. Histopathological examination revealed a low-grade medullary thyroid carcinoma (MTC) in the left lobe and classical papillary thyroid carcinoma (PTC) in the right lobe, with PTC metastasis in the cervical lymph nodes and concurrent SLL in the affected lymph nodes.

[RESULTS] Coexistence of PTC, MTC and SLL in the same patient is rare, there are currently no standardized treatment guidelines due to the limited literature. However, it is essential to consider not only the treatment for each type of tumor but also the potential risks or conflicts associated with the treatments. In the case reported in this paper, the papillary carcinoma invaded the capsule of the right lobe of the thyroid and metastasized to the cervical lymph nodes, warranting radioactive iodine therapy. However, considering the potential negative impact of radioactive iodine on the pre-existing lymphoma, the radioactive iodine therapy was postponed. Meanwhile, constant monitoring of calcitonin and thyroid globulin should be performed to monitor tumor recurrence as was performed in the present case.

[CONCLUSION] Since MTC, PTC, and SLL may coexist, patients with PTC deserve careful surveillance for the other disease entities. This case underscores the need for heightened awareness among clinicians, radiologists, and pathologists regarding the possibility of concurrent thyroid tumors and abnormal lymph nodes, guiding comprehensive pre-operative evaluations and postoperative monitoring strategies. This study aims to provide a warning for routine pathological diagnosis and contribute data for related research.