Prevalence of RET/PTC expression in papillary thyroid carcinoma and its correlation with prognostic factors in a north Indian population

Context : The prevalence of Rearranged during Transfection/Papillary Thyroid Carcinoma (RET/PTC) rearrangement in papillary thyroid carcinoma (PTC) varies in different geographic regions and its prognostic significance remains unclear. Aim : The aim of this study was to recognize the prevalence of RET/PTC expression in PTC from the endemically iodine-deficient region in Northern India and to correlate the expression with the clinicopathologic prognostic factors. Settings and Design : Retrospective. Archival tissue used. Materials and Methods : Immunohistochemistry was performed to look for activated RET protein expression in 50 cases of PTC. No patient had any history of prior irradiation . Statistical Analysis Used : Chi-square method, Student t test, and binary regression method. A P value of < .05 was considered significant for all the tests. Results : The prevalence of RET expression was 44%. Twenty-six (52%) cases showed RET immunoreactivity in histiocytes. Immunoreactivity was the highest in the classic variant of PTC (47.5%), followed by tumors with poorly differentiated areas (25%) and follicular variant (16.7%). RET expression was more prevalent in young patients (45.5 vs. 35.3%), females (43.3 vs. 40.0%), small tumors (33.3 vs. 26.7%), multicentric tumors (36.8 vs. 33.3%), tumors with extrathyroidal invasion (38.9 vs. 32.4%), and regional lymphadenopathy (55.2 vs. 22.2%), while it was less in cases with distant metastases (20 vs. 43.9%). There was no significant correlation of immunoreactivity with any prognostic factor. However, when the cases having immunoreactivity within histiocytes (n=26) and histiocytes + tumor tissue (n=28) were considered, then the expression was significantly more in cases with lymphadenopathy (P values=.009, in both instances). However, the exact clinical significance of RET/PTC positive histiocytes remained unexplained. Conclusions : Prevalence of RET/PTC in our study was consistent with the reported prevalence from other geographic areas. There was no significant correlation with the clinicopathologic factors. However, uniform techniques of detection and large international collaborative studies could clear the uncertainties regarding the prognostic importance of RET/PTC.