Abstract YO25
Case summary
Background: Neuroendocrine tumors (NETs) only account for 1-2% of all neoplasms, most commonly found in the gastrointestinal tract followed by the lung, and is more commonly associated with MEN-1 disease. Mediastinal neuroendocrine tumors, on the other hand, albeit extremely rare, behave more aggressively with a greater tendency for local invasion. TTF-1 positivity is more common among pulmonary NETs while mediastinal NETs frequently have the opposite phenotype. Case: We present a case of a 48 year-old male, with no known co-morbidities and significant smoking history, coming in for a 1 month-history of occasional coughing episodes and throat discomfort. Upon findings of a right paratracheal opacity on chest x-ray, a chest CT scan was requested which showed a large 7.3 x 11.4 x 13 cm heterogeneously enhancing, lobulated mass centered at the anterior mediastinum already compressing the right atrium, left brachiocephalic vein, and the superior vena cava with innumerable vari-sized nodules scattered throughout the lungs with largest measuring 1.7 x 1.3 cm at the left upper lobe. The patient was referred to surgery service and underwent VATS. Immunohistochemical staining revealed positive for chromogranin, synaptophysin and TTF-1, and negative for CD3, CD20 and p40, Ki67 2.6%. The patient was only treated with monthly everolimus.
Conclusion: While the anterior mediastinal mass is larger with more local extension, there was uncertainty regarding the primary site of the tumor because of the unusual positivity for TTF1 for mediastinal NETs compared to lung NETs. While TTF-1 positive, the disease progression and aggressiveness of this case likely points to a mediastinal origin. While synchronous neuroendocrine tumors have been reported (pancreas and ileum), the similarity of morphology and immunohistology of both sites on the background of high specificity of pulmonary NETs for TTF-1, makes this unlikely. The patient’s response was consistent with recent data on everolimus treatment among lung and gastrointestinal NETs, which showed tumor shrinkage in 64% vs 26 % of patients, disease stabilization in 81% vs 64%, and an overall survival of 23.7 months vs 16.5 months.
Clinical trial identification
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Editorial acknowledgement
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