Clinical observation of thyroid metastatic lesion in a patient withrectal cancer

Metastatic lesions of the thyroid gland are extremely rare: in the English-language literature, only 24 clinical cases of colorectal cancer metastasis to the thyroid gland were previously reported. We present a rare clinical case of metastatic thyroid carcinomatosis in a 39-year-old female patient who underwent combined treatment for rectal cancer. In 2018, the patient underwent a laparoscopic-assisted anterior resection of the rectum, with extended lymphadenectomy and preventive ileostomy for rectal cancer (adenocarcinoma), followed by 8 courses of chemotherapy. For the first time, a node in the right lobe of the thyroid gland was detected in August 2020, at the same time a fine-needle aspiration biopsy was performed, the cyto logical picture of which was characteristic of papillary carcinoma, class VI according to Bethesda. In September 2020, the patient underwent surgery in the amount of thyroidectomy, lymphadenectomy III, IV, VI levels of the neck on the right. In order to clarify the histogenesis of tumor foci, an immunohistochemical study was performed (SK-7, SK-20, CDX-2 (DAK-CDX-2), SATB-2 (EP281)). Histological examination of the right lobe of the thyroid gland revealed a metastasis of low-grade adenocarcinoma of the intestinal type with a desmoplastic reaction of the stroma, extensive foci of necrosis, and tumor thrombi in the lumen of blood and lymphatic vessels. In 3 lymph nodes, metastases of poorly differentiated adenocarcinoma with subtotal replacement of lymph node tissue were also detected.