Diffuse Thyroid Metastasis From Lung Cancer Mimicking Thyroiditis on 99mTc-Pertechnetate Scintigraphy

Area of Science:

• Endocrinology
• Oncology
• Nuclear Medicine

Background:

• Thyroiditis is an inflammation of the thyroid gland, often presenting with abnormal thyroid hormone levels.
• Tc-pertechnetate scintigraphy is a nuclear medicine imaging technique used to assess thyroid function and uptake.

Observation:

• A 56-year-old male presented with a sore throat, decreased serum thyroid hormone, and absent Tc-pertechnetate uptake in the thyroid gland.
• Initial suspicion was for thyroiditis based on these laboratory and imaging findings.

Findings:

• Further examination revealed the thyroid gland was completely replaced by metastatic lung adenocarcinoma.
• The absence of Tc-pertechnetate uptake was attributed to the tumor replacing normal thyroid tissue.

Implications:

• This case highlights the importance of considering metastatic disease in the differential diagnosis of apparent thyroid dysfunction.
• Metastatic lung cancer can mimic thyroiditis, underscoring the need for comprehensive diagnostic evaluation.
• Accurate diagnosis is crucial for appropriate treatment and management of patients with unexplained thyroid abnormalities.