Case report describes misdiagnosis of papillary thyroid cancer

The importance of correctly pinpointing papillary thyroid cancer (PTC) was recently highlighted in a case report describing the misdiagnosis of the disease as carcinoma of the lungs.

The paper, which appears in the journal Thyroid, centered on a 54-year-old woman who had been treated for non-small cell lung cancer six years prior to the study. At the time, doctors had labeled her disease a stage IV pulmonary carcinoma, the most serious form of the condition.

Generally, stage IV lung cancer has an exceedingly poor outlook. Only an estimated 1 percent of patients diagnosed with this form of the illness can be expected to survive long term, according to a study published in the journal Radiologic Clinics of North America.

Thus, the patient's continued survival after treatment gave physicians pause, ultimately prompting them to run a series of diagnostic tests to assess the woman's physical condition.

After administering fludeoxyglucose - a radioactive compound that is absorbed by metabolically active areas in the body, like tumors - and using ultrasounds and a fine needle aspiration biopsy, the team discovered that the woman had PTC.

She had, in fact, had PTC as her primary form of cancer the entire time. The lung cancer was actually a metastatic migration of thyroid carcinoma cells.

Researchers determined that the misdiagnosis occurred when an initial lung biopsy tested positive for the increased presence of thyroid transcription factor-1 (TTF-1), a protein that regulates gene transcription for both thyroid and lung cells.

Physicians immediately gave the woman a complete thyroidectomy. They also removed the gland's neighboring lymph nodes and conducted a lymph node dissection to check for any further metastasis.

"Because TTF-1 expression is seen in both thyroid and lung cancers," the study's authors concluded, "careful consideration should be given to both malignancies when evaluating patients with thyroid and pulmonary nodules."

Combined, thyroid and lung cancers are diagnosed in more than 267,000 Americans each year, according to the National Cancer Institute. 

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