Abstract
< strong > Objective: < /strong > Medullary thyroid carcinoma (MTC) is a rare tumor originating from parafollicular C cells. It has more aggressive biologic behavior than differentiated thyroid carcinomas, and it is insensitive to treatment with radioactive iodine. Vandetanib and cabozantinib are the newly approved tyrosine kinase inhibitors in advanced stages, but novel effective systemic therapeutics could be crucial and needed for the clinical management of these patients. We aimed to evaluate the Programmed death-ligand 1 (PD-L1) expression, which is a novel immunotherapy target, in our MTC cohort, and determine whether it has an association with clinical and pathological features. < strong > Material and Method: < /strong > This retrospective study involved 41 cases of MTC with a median follow-up of 54 months. PD-L1 monoclonal antibody (SP263 clone) was investigated immunohistochemically. Complete and/or partial membranous staining pattern in more than 1% of tumor cells was considered positive. The correlations of PD-L1 expression with clinicopathologic and prognostic features were analyzed. < strong > Results: < /strong > PD-L1 positivity was detected in 5 (12.2%) of 41 tumors. The extent of PD-L1 staining was low ( < 5%) for all tumors. There was no clinicopathologic and prognostic relevance regarding PD-L1 expression in our MTC patients. < strong > Conclusion: < /strong > Although PD-L1 expression could be a potential biomarker to predict the prognosis of various cancers and response to checkpoint inhibitors, we did not find any significant correlation between PD-L1 expression and clinicopathologic features in our cases. Studies with larger patient numbers are still required to perform a more comprehensive analysis.
Highlights
Medullary thyroid cancer (MTC) is a rare neuroendocrine tumor originating from calcitonin-producing parafollicular C cells of the thyroid gland
The expression of Programmed death-ligand 1 (PD-L1) in thyroid cancers originating from follicular cells has been investigated in many recent studies, and the rates of PD-L1 positivity vary between 6.1% and 82.5% in thyroid carcinomas originated from follicular cells [13]
The investigator found that PD-L1 positivity was higher in anaplastic thyroid carcinoma than in papillary thyroid carcinoma and follicular thyroid carcinoma, and it is associated with a worse prognosis and aggressive tumor behavior [13]
Summary
Medullary thyroid cancer (MTC) is a rare neuroendocrine tumor originating from calcitonin-producing parafollicular C cells of the thyroid gland. We aimed to investigate PD-L1 expression in MTC patients treated at our university hospital. There was no correlation between PD-L1 negative and positive patients based on clinicopathological characteristics, including age, sex, tumor size, multifocality, surgical margin, pT stage, pN stage, initial lymph node metastasis, recurrence, and relation with chronic lymphocytic thyroiditis (p>0.05).
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