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Comparison of 2- and 3-category histologic grading systems for predicting the presence of metastasis at the time of initial evaluation in dogs with cutaneous mast cell tumors: 386 cases (2009–2014)

Damiano StefanelloDepartment of Veterinary Sciences and Public Health, Faculty of Veterinary Medicine, University of Milan, 20133 Milan, Italy.

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Paolo BuraccoDepartment of Veterinary Sciences, Faculty of Veterinary Medicine, University of Turin, 10124 Turin, Italy.

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Silvia SabattiniDepartment of Veterinary Medical Sciences, University of Bologna, Bologna 40064, Italy.

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Riccardo FinotelloSmall Animal Teaching Hospital, School of Veterinary Science, University of Liverpool, Liverpool, Merseyside, L69 3BX, England.

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Chiara GiudiceDepartment of Veterinary Sciences and Public Health, Faculty of Veterinary Medicine, University of Milan, 20133 Milan, Italy.

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Valeria GriecoDepartment of Veterinary Sciences and Public Health, Faculty of Veterinary Medicine, University of Milan, 20133 Milan, Italy.

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Selina IussichDepartment of Veterinary Sciences, Faculty of Veterinary Medicine, University of Turin, 10124 Turin, Italy.

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Massimiliano TursiDepartment of Veterinary Sciences, Faculty of Veterinary Medicine, University of Turin, 10124 Turin, Italy.

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Timothy ScaseBridge Pathology Ltd, 637 Gloucester Rd, Bristol, BS7 0BJ, England.

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Stefano Di PalmaIdexx Laboratories Italy srl, Via Antonio Canova 27, 20145 Milano, Italy.

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Giuliano BettiniDepartment of Veterinary Medical Sciences, University of Bologna, Bologna 40064, Italy.

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Roberta FerrariDepartment of Veterinary Sciences and Public Health, Faculty of Veterinary Medicine, University of Milan, 20133 Milan, Italy.

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Marina MartanoDepartment of Veterinary Sciences, Faculty of Veterinary Medicine, University of Turin, 10124 Turin, Italy.

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Francesca GattinoDepartment of Veterinary Sciences, Faculty of Veterinary Medicine, University of Turin, 10124 Turin, Italy.

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Mary MarringtonSmall Animal Teaching Hospital, School of Veterinary Science, University of Liverpool, Liverpool, Merseyside, L69 3BX, England.

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Monica MazzolaClinica Veterinaria Gran Sasso, Via Donatello 26, 20131 Milano, Italy.

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Maria Elisabetta VasconiCentro Veterinario Torinese, Lungo Dora Colletta 147, 10153 Turin, Italy.

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Maurizio AnnoniClinica Veterinaria Tibaldi, Viale Tibaldi 66, 20136 Milano, Italy.

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Laura MarconatoCentro Oncologico Veterinario, Via San Lorenzo 1/4, 40037 Sasso Marconi, Italy.

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Abstract

Objective—To compare the Kiupel (2 categories) and Patnaik (3 categories) histologic grading systems for predicting the presence of metastasis at the time of initial examination in dogs with cutaneous mast cell tumors (MCTs).

Design—Retrospective case series.

Animals—386 client-owned dogs with cutaneous MCTs.

Procedures—Medical records of dogs with newly diagnosed, histologically confirmed cutaneous MCTs that had undergone complete clinical staging were reviewed for clinical and histopathologic data.

Results—All Patnaik grade 1 MCTs (n = 52) were classified as Kiupel low-grade MCTs, and all Patnaik grade 3 MCTs (43) were classified as Kiupel high-grade MCTs. Of the 291 Patnaik grade 2 MCTs, 243 (83.5%) were classified as Kiupel low-grade tumors, and 48 (16.5%) were classified as Kiupel high-grade MCTs. Dogs with Patnaik grade 3 MCTs were significantly more likely to have metastases at the time of initial examination than were dogs with grade 1 or 2 MCTs (OR, 5.46), and dogs with Kiupel high-grade MCTs were significantly more likely to have metastases than were dogs with Kiupel low-grade MCTs (OR, 2.54). However, 3 of 52 (5.8%) dogs with Patnaik grade 1 tumors, 48 of 291 (16.5%) dogs with Patnaik grade 2 tumors, and 44 of 295 (14.9%) dogs with Kiupel low-grade tumors had metastatic disease.

Conclusions and Clinical Relevance—Findings indicated that in dogs with cutaneous MCTs, prognostication should not rely on histologic grade alone, regardless of grading system used, but should take into account results of clinical staging.

Abstract

Objective—To compare the Kiupel (2 categories) and Patnaik (3 categories) histologic grading systems for predicting the presence of metastasis at the time of initial examination in dogs with cutaneous mast cell tumors (MCTs).

Design—Retrospective case series.

Animals—386 client-owned dogs with cutaneous MCTs.

Procedures—Medical records of dogs with newly diagnosed, histologically confirmed cutaneous MCTs that had undergone complete clinical staging were reviewed for clinical and histopathologic data.

Results—All Patnaik grade 1 MCTs (n = 52) were classified as Kiupel low-grade MCTs, and all Patnaik grade 3 MCTs (43) were classified as Kiupel high-grade MCTs. Of the 291 Patnaik grade 2 MCTs, 243 (83.5%) were classified as Kiupel low-grade tumors, and 48 (16.5%) were classified as Kiupel high-grade MCTs. Dogs with Patnaik grade 3 MCTs were significantly more likely to have metastases at the time of initial examination than were dogs with grade 1 or 2 MCTs (OR, 5.46), and dogs with Kiupel high-grade MCTs were significantly more likely to have metastases than were dogs with Kiupel low-grade MCTs (OR, 2.54). However, 3 of 52 (5.8%) dogs with Patnaik grade 1 tumors, 48 of 291 (16.5%) dogs with Patnaik grade 2 tumors, and 44 of 295 (14.9%) dogs with Kiupel low-grade tumors had metastatic disease.

Conclusions and Clinical Relevance—Findings indicated that in dogs with cutaneous MCTs, prognostication should not rely on histologic grade alone, regardless of grading system used, but should take into account results of clinical staging.

Contributor Notes

Presented in part at the Annual European Society of Veterinary Oncology Congress, Vienna, May 2014.

Address correspondence to Dr. Marconato (marconato@centroncologicovet.it).