[Thyroid Transcription Factor-1 is Useful for Identifying Primary Tumors]

Area of Science:

• Oncology
• Pathology
• Radiology

Background:

• A 67-year-old male with a history of liver resection for intrahepatic cholangiocarcinoma presented with a growing pulmonary nodule.
• Initial diagnosis of intrahepatic cholangiocarcinoma was based on prior liver resection pathology.

Observation:

• Computed tomography (CT) scan revealed gradual enlargement of a pulmonary nodule in the left S1+2 region.
• Intraoperative rapid pathology indicated metastasis to lymph node (LN) #3, suggesting a potential spread from the initial diagnosis.

Findings:

• Postoperative pathological diagnosis, aided by thyroid transcription factor-1 (TTF-1) staining, revealed primary lung cancer.
• The liver lesion was also confirmed as metastatic lung cancer using TTF-1 staining, revising the initial diagnostic pathway.

Implications:

• This case highlights the importance of TTF-1 staining in differentiating primary lung cancer from metastatic disease, especially in patients with a history of other malignancies.
• Accurate pathological diagnosis is crucial for appropriate treatment strategies and patient management in complex oncological cases.
• The findings underscore the potential for misdiagnosis when relying solely on initial pathological assessments without confirmatory markers like TTF-1 in cases of suspected metastasis.