Background: Thyroid neoplasm is the commonest endocrine neoplasm. More than 80% of thyroid malignancies are papillary thyroid carcinoma (PTC) followed by follicular carcinoma (FC). The diagnosis of papillary thyroid carcinoma is based on characteristic nuclear morphology of a thyroid neoplasm. In contrast, follicular variant of PTC may cause, if the nuclear features of PTC are insufficiently appreciated, severe problems in differentiating from follicular thyroid carcinoma. Several immunohistochemical (IHC) markers such as P63 and CD56 have been recommended to differentiate between this two thyroid malignancies with overlapping histomorphology. Objectives: Our aim was to identify the possible diagnostic role of P63 and CD56 immunoexpression that distinguish PTC, including the follicular variant from follicular thyroid carcinoma. Methods: This cross-sectional descriptive study was conducted in the Department of Pathology, Rajshahi Medical College from March 2020 to February 2022. A total of 44 cases, histologically confirmed as papillary and follicular thyroid carcinoma were included in the study. Immunohistochemistry was done for P63 and CD56 from selected paraffin blocks. Results: Histologically, 39 cases were diagnosed as papillary thyroid carcinoma (27 were classical PTC & 12 were FVPTC) and the rest 5 were follicular thyroid carcinoma. In this study, mean age of the patients was 40.86 ± 6.57 years (SD) and male to female ratio was 1:2.4. P63 showed 74.4% positivity with papillary thyroid carcinoma. Positive immunoreactivity of P63 was highly significant in distinguishing papillary from follicular thyroid carcinoma (P=0.003). Combined P63 positive CD56 negative (P=0.048) and P63 negative CD56 negative immunoexpression (P=0.039) were statistically significant in differentiating papillary from follicular thyroid carcinoma. Conclusion: This study suggested that the use of P63 and CD56 may be helpful in the diagnosis of papillary and follicular thyroid carcinoma along with histopathological examination and their combination may also help in this purpose.
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