Isolated metastasis of the bowel from undifferentiated thyroid carcinoma. A case report and a literature review.

In this article, we aim to demonstrate that thyroid carcinoma can metastasize to the small bowel. This case report involves a 66-year-old woman who underwent total thyroidectomy surgery in 2019, with histopathology revealing a 3A undifferentiated thyroid cancer. She presented with symptoms of bowel obstruction, including abdominal pain, nausea, and vomiting. Thyroid carcinoma accounts for less than 4% of all malignant neoplasms, making it the most common endocrine malignancy. The predominant type is papillary carcinoma, which generally has a favorable prognosis. In contrast, poorly differentiated thyroid cancers have a poor prognosis, with a 5-year postoperative survival rate of 66%. Common metastatic sites include the lungs, brain, and bones, with rare occurrences in organs such as the kidneys, spleen, adrenal glands, and ovaries. Intestinal metastases are extremely rare, with fewer than 15 cases of gastrointestinal localization documented in the literature. This case highlights the rare possibility of thyroid carcinoma metastasizing to the small bowel, emphasizing the need for clinicians to consider metastatic spread in patients with a history of thyroid cancer who present with gastrointestinal symptoms.