Cytologic Criteria for Mast Cell Tumor Grading in Dogs With Evaluation of Clinical Outcome

Abstract

A 2-tiered histologic grading scheme for canine cutaneous mast cell tumors (MCTs) is based on morphologic characteristics of neoplastic cells, including karyomegaly, multinucleation, nuclear pleomorphism, and mitotic figures. Aspirates from MCTs may provide the same information more quickly, inexpensively, and less invasively. This study used these criteria to develop a cytologic grading scheme for canine MCTs to predict outcome. Three anatomic pathologists graded histologic samples from 152 canine MCTs. Three clinical pathologists evaluated aspirates from these masses using similar criteria. A cytologic grading scheme was created based on correlation with histologic grade and evaluated with a kappa statistic. Survival was evaluated with Kaplan-Meier survival curves. Cox proportional hazards regression was used to estimate hazard ratios for tumor grades and individual grading components. Simple logistic regression tested for relationships between risk factors and mortality. The cytologic grading scheme that best correlated with histology (kappa = 0.725 ± 0.085) classified a tumor as high grade if it was poorly granulated or had at least 2 of 4 findings: mitotic figures, binucleated or multinucleated cells, nuclear pleomorphism, or >50% anisokaryosis. The cytologic grading scheme had 88% sensitivity and 94% specificity relative to histologic grading. Dogs with histologic and cytologic high grade MCTs were 39 times and 25 times more likely to die within the 2-year follow-up period, respectively, than dogs with low grade MCTs. High tumor grade was associated with increased probability of additional tumors or tumor regrowth. This study concluded that cytologic grade is a useful predictor for treatment planning and prognostication.

Epidemiological Study of Canine Mast Cell Tumours According to the Histological Malignancy Grade

“…Given the discrepancies in the assessment of the mast cell tumour grade, a new simplified classification system was proposed by Kiupel et al (2011), in which MCTs were divided into low-grade MCTs and high-grade MCTs. The 3-grade classification developed by Patnaik (1984) is still widely used by pathologists (Artuković et al 2014, Leidinger et al 2014, the two-grade system devised by Kiupel et al (2011) is commonly applied as well (Camus et al 2016) or both scales are used simultaneously (Śmiech et al 2016). The present study was based on the standard Patnaik scale, as a majority of the collected material originated from the period before the introduction of Kiupel's two-grade scale.…”

Comparison between May‐Grünwald‐Giemsa and rapid cytological stains in fine‐needle aspirates of canine mast cell tumour: Diagnostic and prognostic implications

“…In primary MCTs, further parameters assessed blindly for both stains were the certainty of MCT diagnosis (yes/no) and the cytological grade of malignancy (low/high) according to Camus et al (2016) …”

“…The cytological diagnosis of mast cell tumour (MCT) is considered among the easiest and most consistent, being based on the identification of the characteristic purple intracytoplasmic granules . Furthermore, cytological grading systems have been recently developed for canine MCTs, which can provide useful prognostic information on tumour biological behaviour at the initial visit, thereby contributing to plan the most appropriate therapeutic strategy . Additionally, MCT staging by cytological examination of regional lymph nodes, spleen, liver and bone marrow plays an essential role in the assessment of true disease extent; this procedure holds a well‐acknowledged prognostic value, and again it is critical for therapy planning …”

“…1,2 Furthermore, cytological grading systems have been recently developed for canine MCTs, which can provide useful prognostic information on tumour biological behaviour at the initial visit, thereby contributing to plan the most appropriate therapeutic strategy. [3][4][5] Additionally, MCT staging by cytological examination of regional lymph nodes, spleen, liver and bone marrow plays an essential role in the assessment of true disease extent; this procedure holds a well-acknowledged prognostic value, and again it is critical for therapy planning. 2,6 Although toluidine blue is considered the best staining method for the demonstration of mast cell granules, 7,8 the cytological diagnosis of MCT is mostly performed on smears stained with methanolic…”

Veterinary Pathology – A Path Forward with New Directions and Opportunities

“…Guidelines and consensus statements have been generated for several diagnostic activities, including reference interval establishment (24), prognostic markers in cancer (25), flow cytometric reporting in canine hematopoietic neoplasia (26), immunocytochemical staining (27), and viscoelastic-based hemostasis testing (28), to name a few examples. Similarly, cytologic (29) and histologic (30, 31) grading schemes have been proposed for various tumors. Importantly, these guidelines are the culmination of efforts of multiple investigators and truly represent a global approach (“One Pathology”).…”