Tohoku J. Exp. Med., 2023 September, 261(1)

Tumor-to-Tumor Metastasis of Medullary Thyroid Carcinoma to Paraganglioma in a Multiple Endocrine Neoplasia Type 2B Patient: A Case Report and Literature Review

Naruhito Takido,¹ Ryusuke Saito,¹ Kaoru Okada,¹ Norifumi Kanai,¹ Yoshihiro Shono,¹ Hiroaki Mitsugashira,¹ Muneyuki Matsumura,¹ Kengo Sasaki,¹ Koji Miyazawa,¹ Atsushi Fujio,¹ Kazuaki Tokodai,¹ Keigo Murakami,² Hironobu Sasano,¹

¹Department of Surgery, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
²Department of Pathology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan

Tumor-to-tumor metastasis is a rare phenomenon in which primary tumor cells metastasize to other tumors. Herein, we report an extremely rare case of tumor-to-tumor metastasis of medullary thyroid carcinoma to a paraganglioma in a patient with multiple endocrine neoplasia type 2B. Based on genetic examination, a 36-year-old woman was diagnosed with multiple endocrine neoplasia type 2B when she was 24 years old. She had a history of total thyroidectomy for medullary thyroid carcinoma and bilateral adrenalectomy for pheochromocytomas, which were performed when she was 15 years and 29 years old, respectively. Follow-up computed tomography demonstrated a retroperitoneal tumor of 30 mm in diameter beside the left kidney and a liver tumor of 16 mm in diameter located in segment 6. The retroperitoneal and liver tumors were surgically resected and examined by a pathologist. Histological examination revealed the classic Zellballen pattern in the retroperitoneal tumor, rendering the diagnosis of a paraganglioma recurrence. Inside the tumor, a white nodule positive for carcinoembryonic antigen, weakly positive for calcitonin, and negative for tyrosine hydroxylase, was identified and diagnosed as a metastatic medullary thyroid carcinoma with high malignant potential. The liver lesion was diagnosed as a metastasis of the medullary thyroid carcinoma. This is the first report of tumor-to-tumor metastasis of medullary thyroid carcinoma to paraganglioma in a patient with multiple endocrine neoplasia type 2B twenty years after total thyroidectomy.

Key words —— calcitonin; medullary thyroid carcinoma; multiple endocrine neoplasia type 2B; paraganglioma; tumor-to-tumor metastasis

© 2023 Tohoku University Medical Press

===============================

Tohoku J. Exp. Med., 2023 September, 261(1), 75-81.

Correspondence: Ryusuke Saito, Department of Surgery, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8574, Japan.

e-mail: ryusuke009009@gmail.com