SHM Converge Scientific Abstract ePoster Gallery-Beyond Recurrence: Distinguishing New Lung Primary From Remote Thyroid Carcinoma in a Diagnostic Crossroad

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This case describes a 56-year-old Vietnamese woman, a lifelong nonsmoker, with remote papillary thyroid carcinoma treated in 2008 and persistently undetectable thyroglobulin. She presented with dyspnea, orthopnea, and weight loss, and imaging showed a large right pleural effusion. After thoracentesis drained 1.5 L, CT revealed enlarging right lung nodules.<br /><br />Initial biopsy showed malignant cells positive for AE1/AE3, CK7, and TTF-1, which raised concern for recurrent thyroid cancer versus lung adenocarcinoma. To avoid anchoring bias, the team expanded the immunohistochemical workup. Napsin A positivity supported a diagnosis of a new primary lung adenocarcinoma rather than thyroid recurrence. Brain staging was negative.<br /><br />She was initially treated with carboplatin, pemetrexed, and pembrolizumab. Molecular testing later identified PD-L1 expression and an EGFR mutation, leading to a switch to osimertinib. She remains on osimertinib with stable disease on follow-up CT.<br /><br />The report emphasizes several diagnostic lessons: patients with remote cancer histories and malignant pleural effusions are at risk for anchoring bias, especially when immunohistochemical markers overlap across tumor types. Papillary thyroid carcinoma rarely recurs after more than 10 years when thyroglobulin remains undetectable. Large pleural effusions can also hide underlying lung lesions, making repeat imaging after drainage important. The authors recommend using broad diagnostic panels, coordinated imaging, pathology, and molecular testing, and maintaining vigilance for second primary malignancies in cancer survivors.

Asset Subtitle

Bhavika Agrawal

Meta Tag

Author List Bhavika Agrawal, Sivaguha Yadunath Prabhakaran, Tulsi Bhatt

Category Clinical Vignettes

Concept Papillary Thyroid Carcinoma

Concept Primary Lung Adenocarcinoma

Concept Clinical History

Concept Imaging

Concept Immunohistochemistry

Distinguished Non-Finalist

Presenter Organization Mercy Catholic Medical Center

Presenting Author Bhavika Agrawal

Track Adult

Keywords

papillary thyroid carcinoma

lung adenocarcinoma

malignant pleural effusion

anchoring bias

immunohistochemistry

TTF-1

Napsin A

EGFR mutation

osimertinib

second primary malignancy

Papillary Thyroid Carcinoma

Primary Lung Adenocarcinoma

Clinical History

Imaging

Immunohistochemistry