Substantial Interobserver Variation Among Morphopathological Diagnosis Of Canine Mammary Gland Tumours From Veterinary And Human Pathologists

摘要

Because the morphopathological diagnosis for the benignity or malignance of tumours has played a key role of therapeutic decisions and prognosis, the reproducibility and coherence among pathologists is important. To determine the level of interobserver variation for comparative studies among veterinary and human pathologists for the diagnosis of canine mammary gland tumours (MGTs), one hundred and thirty-six selected canine MGTs with histological slides were randomly divided into two groups: 68 cases were evaluated independently by three veterinary pathologists and one human pathologist; other 68 cases were reviewed blindly by one veterinary pathologists and three human pathologists. All the participating pathologists designated whether the canine MGTs are benign or malignant. Kappa (κ) statistics were calculated to evaluate the level of agreement. For three human pathologists involved in this study, moderate to good levels of agreement among their diagnosis (κ=0.68-0.81). However, three veterinary pathologists participated in this study show less than chance to slight levels agreement (κ= -0.06 to 0.25). In this study, human pathologists tend to diagnosed canine MGTs as benign lesions while veterinary pathologists tend to diagnose as malignant lesions. We conclude that substantially high interobserver variations do exist among pathologists and will greatly influence the research result and therefore; internationally accepted pathological diagnostic definitions with high accuracy and reproducibility among pathologists are required to assist global researchers in characterizing the tumour biology, natural history, and the comparison of treatment modalities of canine MGTs. Introduction Pathologists, either in the veterinary medicine or human medicine, play a key role in the diagnosis of tumor or tumour-related lesions. Pathological diagnosis remains the “gold standard” for cancer diagnosis in almost daily practices. Mammary gland tumours are the one of the mostly encountered neoplasm in the female dogs10 and are known for their complex pathological features resulting in misdiagnosis of malignant tumours as benign in about 10% of the tumours13. A few previous studies evaluating prognostic factors for canine MGT, using univariate and multivariate analysis have been conducted but fail to get consistent conclusion 4,5,11,19,22,28,29. Although it has been stressed that prognostic studies of canine MGT were performed based on groups of dogs and their tumours; and, therefore the prognostic significance of tumour histology can’t consistently apply to individual cases. To compare with epidemiological studies of human, the case number of dogs involved in the prognostic studies is significantly lesser 3 and may be an important reason for inconsistent conclusion; however, a major possible reason for this phenomenon is interobserver variation of pathological diagnosis among pathologists.Although diagnosis of canine MGTs posed certain difficulty in veterinary pathologists, no English article discussing about the interobserver variation of canine MGTs in the well-known website PUBMED12 (http://www.ncbi.nlm.nih.gov/pubmed/) to the best of the authors’ search. In contrast to canine MGTs, there were dozens of studies concerning interobserver variation in pathological reports of human breast lesions 2,21,24. The histological classification of canine MGTs has been the subject of eliciting many debates, with various points of view have been proposed 3,6,9,15. The World Health Organization/Armed Forces Institute of Pathology (WHO/AFIP) classification for canine MGTs, published in 1999, is currently the most widely used system worldwide 14. Through years of efforts, less and less diagnostic inconsistency exists among pathologists on the human breast tumours. On the contrary, lesser consensus about canine MGTs do occur and the possibly low reproducibility and coherence of pathological diagnosis on canine MGTs may hamper further tumour-related studies.I