Abstract
Canine cutaneous mast cell tumors (ccMCTs) are currently graded according to Patnaik and Kiupel grading schemes. The qualitative and semiquantitative parameters applied in these schemes may lead to inter- and intraobserver variability. This study investigates the prognostic value of volume-weighted mean nuclear volume (vv¯), a stereological estimation that provides information about nuclear size and its variability. vv¯ of 55 ccMCTs was estimated using the "point-sampled intercept" method and compared with histological grade and clinical outcome. The clinical history of dogs treated with surgical excision alone was available for 30 ccMCTs. Statistical differences in vv¯ were found between grade II (x¯ = 115 ± 29 µm(3)) and grade III ccMCTs (x ¯= 197 ± 63 µm(3)), as well as between low-grade (x ¯= 113 ± 28 µm(3)) and high-grade ccMCTs (x¯ = 184 ± 63 µm(3)). An optimal cutoff value of vv¯ ≥ 150 µm(3) and vv¯ ≥ 140 µm(3) was determined for grade III and high-grade ccMCTs, respectively. In terms of prognosis, vv¯ was not able to predict the clinical outcome in 42% of the cases; however, cases with vv¯ <125 µm(3) had a favorable outcome. These results indicate that, despite having limited prognostic value when used as a solitary parameter, vv¯ is highly reproducible and is associated with histological grade as well as with benign behavior.