Background and Objectives: Oral cancer remains a critical global health concern, with oral squamous cell carcinoma (OSCC) being the most prevalent form. Oral potentially malignant disorders (OPMDs), such as oral leukoplakia (OLK), oral lichen planus (OLP), and actinic cheilitis (AC), often precede OSCC. Identifying reliable biomarkers is vital for assessing malignant transformation risk. The present study aimed to evaluate the immunohistochemical expression of differentiated embryonic chondrocyte 1 (DEC1), a marker of dysplasia severity, and cluster of differentiation 44 (CD44), which is associated with cancer progression, in OPMD and OSCC tissues. Materials and Methods: A retrospective analysis was conducted on 145 biopsy specimens from January 2015 to January 2023, comprising normal mucosa (NM), OLK, OLP, AC, and OSCC. DEC1 and CD44 expression levels were assessed using immunohistochemical staining. Positivity scores were determined based on staining intensity and extent, with statistical analyses performed using SPSS software (SPSS Inc., Chicago, IL, USA, version 29.0 for Windows). Results: It was found that CD44 expression significantly increased across OPMD and OSCC compared to NM (p < 0.001). Conversely, DEC1 expression was consistent across lesion types and dysplasia levels. CD44 expression was the highest in AC and OSCC, underscoring its potential role as a progression marker. Conclusions: The results indicate that CD44 is a more sensitive marker for assessing dysplastic severity and malignant transformation, while DEC1 may serve as a complementary marker for early-stage evaluation. Further research involving larger cohorts is needed to confirm these findings.

Background/Objectives: Oral potentially malignant disorders (OPMDs), including oral leukoplakia (OLK), oral lichen planus (OLP), and actinic cheilitis (AC), have varying risks of progression to oral squamous cell carcinoma (OSCC). Biomarkers such as aldehyde dehydrogenase 1 (ALDH1) and mammary serine protease inhibitor (Maspin) have shown potential for diagnostic and prognostic use in oral cancer. The present study aimed to evaluate the immunoexpression of aldehyde dehydrogenase 1, a cancer stem cell marker associated with aggressiveness, and the mammary serine protease inhibitor, a potential tumor suppressor, in OPMD and OSCC tissues. Methods: A retrospective analysis was performed on 145 biopsy specimens collected from January 2015 to January 2023, including normal epithelium, OPMDs (OLK, OLP, AC), and OSCC. ALDH1 and Maspin expression levels were evaluated using immunohistochemistry, considering both the percentage of positive cells and staining intensity. Statistical analyses were carried out using the Statistical Package for the Social Sciences (SPSS, version 29.0; IBM Corp., Chicago, IL, USA). Results: Normal oral epithelium showed no expression of ALDH1, whereas 40.6% of OPMDs and 44.4% of OSCC samples exhibited high cytoplasmic ALDH1 expression. Nuclear ALDH1 expression was elevated in 29.7% of OPMDs and 38.9% of OSCCs (p < 0.001). Nuclear Maspin expression was high in 95.2% of normal tissues, in 67.2% of OPMDs and in 55.6% of OSCCs (p < 0.001). Maspin showed strong nuclear and cytoplasmic expression in normal tissue, but its expression decreased in OPMDs and OSCCs, with statistically significant reductions in both compartments (p < 0.001). Conclusions: The results indicate that ALDH1 upregulation and Maspin downregulation are hallmark events in oral carcinogenesis. Their combined evaluation provides a powerful tool for assessing dysplastic severity and malignant transformation risk in OPMDs. Future studies on larger cohorts are needed to confirm the prognostic utility of this dual-marker model.