Interobserver reproducibility among neuropathologists and surgical pathologists in fibrillary astrocytoma grading

Many of the problems associated with the current grading approaches for fib rillary astrocytomas center around the lack of consistency in grading. This study compares the diagnoses of five neuropathologists with five experienc ed surgical pathologists with regard to assigning astrocytoma grade. Thirty neoplastic and non-neoplastic lesions were sent to each of five neuropatho logists and five surgical pathologists for placement into one of three grad es as outlined by modified Ringertz schema. Grading criteria (Burger et al. , 1985. Cancer 56:1106-1111) were distributed to all participants, who have been practicing for at least 5 years. An additional category for non-neopl astic or normal tissue was also provided. The diagnoses, based on the major ity opinion of the neuropathologist group, included six low grade astrocyto mas, ii anaplastic astrocytomas, seven glioblastoma multiforme, and six nor mal/reactive lesions. Agreement by all neuropathologists was reached in 12 cases (40%). A discrepant diagnosis was obtained in one of five neuropathol ogists in 14 additional cases (46.7%). In the remaining four cases, two neu ropathologists deviated from the majority opinion; in each of these cases, the diagnostic problem involved differentiating tumor from reactive gliosis . All five surgical pathologists agreed in six cases (20%). One discrepant diagnosis among the surgical pathologist group was seen in seven cases (23. 3%). In the remaining 17 cases, two or more discrepant diagnoses were obtai ned (56.7%); discrepancies in these cases included differences in assignmen t of tumor grade and in distinguishing low grade astrocytoma from gliosis. In conclusion: (1) it is likely that experience with grading accounts for t he better level of agreement among the neuropathologist group (kappa statis tic 0.63) versus the surgical pathologist group (kappa statistic 0.36); (2) in most cases, the neuropathologists all agreed or had one discrepant diag nosis (86.7%) versus the surgical pathologist group (43.3%); (3) the discre pancies in diagnosis among both groups is likely related, in good part, to the limitations of the grading schema in fully enumerating the spectrum of such grading parameters as cytologic atypia and vascular proliferation. (C) 2000 Elsevier Science B.V. All rights reserved.