Interobserver Variation in the Morphopathological Diagnosis of Canine Mammary Gland Tumor Among Veterinary Pathologists

Because morphopathological diagnosis of tumors plays a key role in prognosis and therapeutic decisions, the reproducibility and coherence among pathologists is important. To determine the level of inter-observer variation among veterinary pathologists for the diagnosis of canine mammary gland tumors, 15 canine mammary gland tumor slides were coded and evaluated independently by 10 veterinary pathologists. The pathologists designated whether the canine mammary gland tumors are benign or malignant. Kappa, interpreted as the proportion of agreement among raters, showed varying degrees of agreement among the 10 veterinary pathologists with kappa values ranged between 0 (no agreement) and 1 (complete agreement). Overall, we found only moderate inter-observer agreement among veterinary pathologists (mean kappa=0.43). Therefore, internationally accepted pathological diagnostic criteria of canine mammary gland tumors would assist veterinary pathologists in making more accurate diagnosis of canine mammary gland tumors.