|A total of 141 MCT specimens reported as grade I, II, or III according to the Patnaik system with both histologic specimens and fine-needle aspirates available were histologically and cytologically reevaluated in a retrospective study.
According to the 2-tier grading system, 38 cases were diagnosed histologically as high-grade and 103 as low-grade MCT.
Cytologic grading resulted in 36 high-grade and 105 low-grade tumors.
Agreement between histologic and cytologic grading based on the 2-tier grading system was achieved in 133 cases (sensitivity 86.8%, specificity 97.1%, kappa value 0.853), but 5 high-grade tumors on histology were classified as low-grade on cytology.
Cytologic grading of MCT in the dog is helpful for initial assessment.
However, the reliability of cytology using the 2-tier grading system is considered inadequate at this point.
Prospective studies including clinical outcome should be pursued to further determine diagnostic accuracy of cytologic mast cell grading.
Source: Hergt, F., von Bomhard, W., Kent, M. S. and Hirschberger, J. (2016), Use of a 2-tier histologic grading system for canine cutaneous mast cell tumors on cytology specimens. Veterinary Clinical Pathology. doi: 10.1111/vcp.12387