Cytologic Grading of Canine Mammary Tumors by Robinson's System Adapted to Romanowsky‐Type Rapid Staining: Prognostic Implications

BACKGROUND: Mammary neoplasms are a major concern in intact female dogs, and cytologic examination is routinely used for initial screening. Although the adaptation of Robinson's cytologic grading system to canine species has been scarcely explored, it shows prognostic potential, particularly when correlated with other clinical and pathologic markers. OBJECTIVES: This study aimed to assess the prognostic performance of an adaptation of Robinson's cytologic grading system using rapid Romanowsky-type staining in canine mammary carcinomas. We also investigated its association with prognostic and predictive markers and overall survival. METHODS: Fifty-one cytologic samples from canine mammary tumors were analyzed to evaluate the association between cytologic grade, histopathology, Ki-67 and Cox-2 expression, clinical data, and survival. ROC curve analysis was performed to determine prognostic performance, and principal component analysis (PCA) was used to explore morphologic patterns. RESULTS: Cytologic grade was significantly associated with tumor size, ulceration, and cellular features linked to malignancy but revealed low agreement with histologic grade and demonstrated no significant correlation with Ki-67 and Cox-2 expression. Higher cytologic grades and increased atypia were correlated with reduced survival. Robinson's cytologic score, Ki-67 index, Peña's histologic grade, and ulceration were key variables associated with the biologic and morphologic heterogeneity of the tumors. CONCLUSION: The Robinson cytologic grading system, when adapted to rapid Romanowsky-type staining, has prognostic relevance in canine mammary tumors. When interpreted alongside other clinical and pathologic features, it may contribute to early prognostic stratification and therapeutic planning. The use of larger cohorts in future studies is recommended for their validation.