Immunohistochemical Characterization of 14-3-3σ Expression in Canine Primary Pulmonary Carcinomas: A Preliminary Study

14-3-3σ is a cell-cycle regulatory protein implicated in tumor development and progression, but its expression in canine primary pulmonary carcinomas (CPPC) has not been characterized. This study investigated 14-3-3σ immunohistochemical expression in primary pulmonary carcinomas and its relationship with histological grade, proliferative activity, mitotic count, and tumor volume. Ten CPPCs were examined and graded according to established criteria. Immunohistochemical expression of 14-3-3σ was evaluated using a semiquantitative scoring system, while Ki-67 labeling was assessed by calculating the labeling index. Nine of 10 tumors (90%) showed 14-3-3σ immunoreactivity, which was predominantly multifocal, heterogeneous, and cytoplasmic; nuclear immunoreactivity was observed, particularly in areas showing strong cytoplasmic staining. Exploratory correlation analyses did not identify statistically significant associations between the 14-3-3σ immunohistochemical score and histological grade, Ki-67 labeling index, mitotic count, or estimated tumor volume. The Ki-67 labeling index ranged from 20.4% to 89.5% (median, 35.6%). These findings provide preliminary descriptive data on 14-3-3σ immunoreactivity in CPPCs. Larger studies incorporating quantitative assessment and clinical follow-up are warranted to determine its clinicopathological and prognostic significance.