LAUSR

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 ( v v ¯ ), a stereological estimation that provides information about nuclear size and its variability. v v ¯ 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 v v ¯ were found between grade II ( x ¯ = 115 ± 29 µm3) and grade III ccMCTs ( x ¯ = 197 ± 63 µm3), as well as between low-grade ( x ¯ = 113 ± 28 µm3) and high-grade ccMCTs ( x ¯ = 184 ± 63 µm3). An optimal cutoff value of v v ¯ ≥ 150 µm3 and v v ¯ ≥ 140 µm3 was determined for grade III and high-grade ccMCTs, respectively. In terms of prognosis, v v ¯ was not able to predict the clinical outcome in 42% of the cases; however, cases with v v ¯ <125 µm3 had a favorable outcome. These results indicate that, despite having limited prognostic value when used as a solitary parameter, v v ¯ is highly reproducible and is associated with histological grade as well as with benign behavior.