Rare Metastasis of Gastric Cancer to the Thyroid Gland: A Case Report and Review of Literature

Case report: Unique ultrasound feature of thyroid metastases in occult breast cancer

Occult breast cancer is an uncommon type of breast cancer. Metastases of occult breast cancer to other tissues are rather rare. We present a rare case of thyroid metastases in a 46-year-old woman who underwent occult breast cancer. The first ultrasound (US) examination of the thyroid showed that the left lobe was enlarged but had normal thyroid function. At first, this case was misdiagnosed as thyroiditis based on the thyroid US features. However, the cytological and histological results showed that nests of the neoplastic cells were found. Further immunohistochemistry results confirmed that these neoplasms were derived from breast tissue. Analysis using the successive US scans revealed that the sizes and echo of the thyroid repeatedly changed after the radiotherapy and chemotherapy treatment. To our knowledge, this is the first reported case of occult breast carcinoma presenting with thyroid metastases. This case can easily be misdiagnosed as thyroiditis due to the metastasis area not manifesting as regular suspicious nodules or diffused punctate calcifications.

An Extremely Rare Case of Thyroid Metastasis from Advanced Gastric Cancer

Metastases to the thyroid area are extremely rare in cancer, more specifically, in gastric cancer, where intraperitoneal metastases are absent. Herein, we describe a case of a 41-year-old man who had advanced gastric cancer with metastasis to the right thyroid area, which was found 6 years after curative surgery. The patient presented with multiple enlarged right cervical lymph nodes and a right thyroid mass of 1.2 cm. We assumed that the patient had primary thyroid cancer as he had no signs of other metastases. We performed fine-needle cytology under ultrasonography on the thyroid nodule. However, with a positive carcinoembryonic antigen and a negative thyroid transcription factor 1 immunohistochemical staining results, the patient was diagnosed with metastatic adenocarcinoma that was of gastric origin. Subsequently, the patient was treated with radiotherapy and chemotherapy. This report aimed to raise the concern that gastric cancer may cause metastasis to the peri-thyroid area, involving the thyroid, parathyroid, and regional lymph nodes.

Application of Immunohistochemistry in Papillary Thyroid Carcinoma

Immunohistochemistry (IHC) is an economic and precise method to localize the presence of specific protein at cellular level in tissue. Although many papillary thyroid carcinomas do not require IHC to render a diagnosis, there are certain scenarios in which IHC are important. The major diagnostic applications of IHC include confirmation of papillary thyroid carcinoma in sites other than the thyroid, distinguish papillary thyroid carcinoma from other primary thyroid neoplasms in thyroid, and identify papillary thyroid carcinoma from secondary tumors to the thyroid. At research level, IHC could help identify prognostic information, identify underlying genetic alterations, and predict response to treatment in papillary thyroid carcinoma. The understanding of principle and recent advances in IHC will improve the diagnosis and management of patients with thyroid lesions including papillary thyroid carcinoma.