Co-Occurrence of Differentiated Thyroid Cancer and Second Primary Malignancy: Correlation with Expression Profiles of Mismatch Repair Protein and Cell Cycle Regulators

Abstract

Some patients with thyroid cancer develop a second primary cancer. Defining the characteristics of patients with double primary cancers (DPCs) is crucial and needs to be followed. In this study, we examine molecular profiles in DPC. We enrolled 71 patients who received thyroid cancer surgery, 26 with single thyroid cancer (STC), and 45 with DPC. A retrograde cohort was used to develop immunohistochemical expressions of mismatch repair (MMR) proteins and cell-cycle-related markers from tissue microarrays to produce an equation for predicting the occurrence of DPC. The multivariate logistic model of 67 randomly selected patients (24 with STC and 43 with DPC) identified that the expression of deficient MMR (dMMR) (odds ratio (OR), 10.34; 95% confidence interval (CI), 2.17-49.21) and pRb (OR, 62.71; 95% CI, 4.83-814.22) were significantly associated with a higher risk of DPC. In contrast, the expression of CDK4 (OR, 0.19; 95% CI, 0.04-0.99) and CDK6 (OR, 0.03; 95% CI, 0.002-0.44) was significantly associated with a lower risk of DPC. Collectively, dMMR, pRb, CDK4, and CDK6 have a sensitivity of 88.9% (95% CI, 75.1-95.8) and a specificity of 69.2% (95% CI, 48.1-84.9) for occurrence of DPC in all 71 patients. This is the first report to demonstrate the molecular differentiation of STC and DPC. Overall, the integral molecular profile performed excellent discrimination and denoted an exponential function to predict the probability of DPC.

Keywords: DNA mismatch repair; cell cycle; immunohistochemistry; multiple primary; neoplasms; second primary; thyroid neoplasms.

Figure 1

Representative images and distribution of the investigative markers. The microarray cores exhibited features of papillary carcinoma (upper panels) and follicular carcinoma (lower panels). The cores of thyroid cancer tissue showed strong expression of cyclin D1 and p21, while loss of expression of CDK4.

Figure 2

Expression pattern of MMR proteins. Panel (A): The tumor sample from papillary carcinoma showed dMMR status with complete loss of nuclear staining for MLH1 and PMS2. Panel (B): The tumor sample from follicular carcinoma exhibited an MMR-proficient status with intact nuclear staining for MMR proteins.

Figure 3

Representative immunohistochemical staining for the expression of pRb, CDK4, CDK6, and MMR proteins in the double primary cancer (DPC) group. Papillary carcinoma (left upper panel; H&E stain) showed high expression of pRb, while most cancer cells were negative for CDK4 and CDK6. Tumor tissue demonstrated deficient mismatch repair (dMMR) with loss of MLH1 and PMS2 expression.

Figure 4

The analysis of the receiving operating characteristics curve demonstrating the ability of the combined predictive model (dMMR phenotype, pRb expression and lack of CDK4 or CDK6) to discriminate the DPC group.