# Traveling together! - Intrathymic thyroid tissue in a patient with Graves’ disease

## TL;DR

A rare case of thyroid tissue found inside the thymus in a patient with Graves' disease is reported.

## Contribution

This report adds to the limited literature on intrathymic ectopic thyroid tissue in the context of Graves' disease.

## Key findings

- Intrathymic thyroid tissue was identified in a 52-year-old African-American woman with Graves' disease.
- The mass was confirmed histologically as thyroid follicles surrounded by normal thymic tissue.
- The case highlights the rarity of intrathymic ectopic thyroid tissue.

## Abstract

Ectopic thyroid tissue is rare in the general population and more prevalent in people who have existing thyroid disease. Common anatomical sites of ectopic thyroid tissue include the lateral cervical region, thyroglossal duct, mediastinum, lingual, sublingual, and submandibular region. Intrathymic ectopic thyroid tissue is exceedingly rare. The purpose of this report is to describe one such case in a 52-year-old African-American female with Graves’ disease. The patient presented for a physical exam and follow-up. During the exam, an incidental mediastinal mass was discovered, which was evaluated by imaging studies and subsequently was resected. Histologically, the mass was composed of variable-sized thyroid follicles lined by a monolayer of cuboidal to columnar follicular epithelial cells and filled with eosinophilic colloid, surrounded by a rim of unremarkable compressed thymic tissue.