A 60-year-old female presented to the hospital with a large painless pre-sternal swelling and it left the doctors completely puzzled regarding its diagnosis.
The woman had the swelling for 2 years. According to her, it was painless. However, the swelling had increased in size over time. On her presentation, the woman displayed normal vitals and did not have any symptoms. Doctors examined her pre-sternal swelling and did not find any extension in the retro-sternal region. The swelling was localized in front of the sternal area. However, it did involve the strap muscles of the right side. Overall, the swelling was non-tender on touch and did not cause any serious difficulties.
Pre-sternal Swelling: Can it be Thyroid?
While taking the history of the patient, the woman revealed that she underwent surgery for papillary carcinoma of the thyroid, a decade ago. Furthermore, she was on a daily dose of thyroxine ever since. This information alerted the doctors to a possible recurrence of cancer.
They carried an ultrasound of the swelling and it revealed cystic areas within the swelling. To confirm the cytological characteristics, they also performed FNAC. However, they failed to get any conclusive results. Thus, the doctors further performed CT and MRI to establish a diagnosis. The radiological results revealed a multicystic mass with both solid and cystic components along with the mass infiltrating the right sternocleidomastoid and strap muscles. They treatment plan was based on the suspicion of a possible recurrence of thyroid carcinoma.
Doctors widely excised the mass along with the lymph node that they palpated on neck examination. They also removed some parts of the sternocleidomastoid that was attached to the mass. They sent the mass for histopathology which confirmed papillary carcinoma of the thyroid. The specimen consisted of typical cells, hemosiderin-filled macrophages and areas of necrosis. The dissected lymph node also came out positive for cancer. It had both cancerous infiltrates and fibrous tissue.
Doctors put the patient on extensive radioiodine therapy to achieve complete remission from cancer. They also kept the patient on strict follow-up with regular assessment for thyroglobulin levels.
Papillary Thyroid Cancer
Papillary thyroid carcinoma constitutes the greatest percentage of thyroid cancers. It involves the formation of a solid or cystic component within the parenchyma of the gland which manifests itself as a swelling on the outside.
Papillary cancers of the thyroid spread very easily to other organs. Most commonly, they involve the lungs, liver and bones and they do so by using the lymphatics route. However, their prognosis remains good (5 years survival rate is nearly 100%). Lymphatic involvement only increases the chances of recurrence and does not seem to have any serious impact on patient survival.
Pre-sternal Swelling: How Does the Thyroid Descend?
There are many documented cases of sternal goitres. However, almost all of them take a retro-sternal position. According to a theory, these thyroids are pulled downwards by a negative intrathoracic pressure created during acts such as swallowing and respiration. While going downwards, the thyroid takes its blood supply from the inferior thyroid artery that remains in the cervical region and does not descend. Nevertheless, it keeps increasing in size and goes on to involve the strap muscles too.
The literature only describes a few cases of presternal thyroid extension. Even less, in which the thyroid forms a mass in front of the sternum. Researchers put forward different theories to explain circumstances in which the thyroid can grow into a pre-sternal position. Some say that thyroid cells migrate and invade the strap muscles and then go on to form a pre-sternal swelling/mass. Others suggest that this type of mass develops from an ectopic thyroid tissue located in pre-sternal space. Another popular belief says that it can develop from a remnant thyroid tissue left after an improper thyroidectomy. Whatever the exact aetiology may be, most cases in which it forms a pre-sternal mass turn out as papillary carcinomas on histology. Thus, they warrant careful resection with strict follow-up to achieve complete remission.