Stereology in Grading and Prognosis of Canine Cutaneous Mast Cell Tumors

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