Immunohistochemical analysis of vocal cord polyps applying markers of squamous cell carcinogenesis

The aim of the study was to perform a pathohistological and immunohistochemical analysis of squamous cell (SC) carcinogenesis markers on epithelial linings of vocal cord polyps. The vocal box, being a heavily burdened organ with intensive cell renewal and regenerative processes, is therefore a favourable environment for constant epithelial growth and hyperplasia. In our ongoing projects on laryngeal carcinogenesis and research on laryngeal tissue, we encountered atypia on diagnosed nodules and polyps that are usually considered as benign formations, resulting from the above-mentioned cell renewal and regeneration, which lead to further investigation. The purpose was to see if changes in molecular markers of SC carcinogenesis follow, or, may appear in immunohistochemical (IHC) analysis, before histological atypia in standard haematoxylin-eosin (HE) staining, and contribute in early diagnosis of potentially suspect polyps.

After classical pathohistological (PH) analysis on HE slides, IHC analysis of EGFR, cyclin D1, p53, Ki-67, and IMP3 was performed on tissue microarrays of laryngeal tissue (50 samples), ranging from normal to hyperplastic lesions with no atypia (34 samples), low-grade atypia (11 samples), and high-grade atypia (5 samples).

This study established an increase and correlation of EGFR, cyclin D1, p53, Ki-67 and IMP3 IHC expressions with pathohistological findings of dysplasia in glottic polypoid lesions. Low and high-grade dysplasia had statistically higher percentages of EGFR-positive cells than normal epithelium and simple hyperplasia (SH) (low vs. normal/SH P = 0.007; high vs. normal/SH P = 0.001). High-grade dysplasia had statistically more positive cells than low-grade dysplasia (P = 0.004), and low-grade dysplasia had statistically more positive cells than specimens without atypia (P = 0.007). The percentage of positive cells was statistically higher for cyclin D1, p53 and Ki-67 in high-grade dysplasia versus low-grade dysplasia (cyclin D1 P = 0.011, p53 P = 0.002; Ki-67 P = 0.026; respectively) and versus normal epithelium and SH (cyclin D1 P = 0.003; p53 P = 0.001; Ki-67 P = 0.002; respectively). An increase of IMP3-positive cells with an increase of atypical changes in the laryngeal epithelium, from superficial towards basal layers was noticed, contrary to the usually seen positivity pattern of SC carcinogenesis markers from basal to superficial layers. A statistically significant difference of IMP3 IHC staining between the pathohistological groups (P = 0.003) was recorded.

Only polyps that present with simple hyperplasia as the greatest mucosal change can be considered as benign formations. Pathohistologically detected atypia in polypoid changes of vocal cords, confirmed by molecular atypia with an increase of SC carcinogenesis markers, suggest their inclusion in studies of laryngeal carcinogenesis. Our results suggest that in problematic cases IHC analysis could be of interest in detection of biological aggressiveness in polypoid laryngeal tissue and beneficiary for polyp patients' follow-up. Further research of laryngeal carcinogenesis markers and their meaning in fibrovascular polyps is of interest.