Feline intestinal mast cell tumours: clinicopathological characterisation and KIT mutation analysis.
OBJECTIVE
Feline intestinal mast cell tumours (FIMCTs) are rare and reportedly characterised by poor differentiation, aggressive biological behaviour and lack of reliable therapeutic aids. KIT proto-oncogene-activating mutations have never been investigated in these tumours. This study describes the main clinicopathological and microscopic features observed in 17 FIMCTs.


METHODS
Tumour degree of differentiation, proliferative activity, Kit protein expression and KIT mutations were evaluated and correlated with survival to assess their prognostic relevance.


RESULTS
Ten tumours were located in the small intestine, two in the ileocaecocolic junction, and five in the large intestine. Survival times ranged from 3-538 days. Fifteen tumours were evaluated histologically, and there were six well-differentiated, six moderately differentiated and three poorly differentiated FIMCTs. The last showed a medium-to-large deposition of collagen tissue (P <0.001), and significantly higher mitotic and Ki67 indexes compared with more differentiated tumours (P = 0.011). On survival analysis, tumour degree of differentiation (P <0.001) and a mitotic index >2 (P = 0.022) were significantly associated with decreased survival times. Twelve cases showed Kit protein immunoexpression. The Kit pattern was membranous in five cases (33.3%), focal paranuclear in five (33.3%) and diffuse cytoplasmic in two (13.3%). Cytoplasmic Kit patterns were associated with a lesser differentiation (P = 0.015). Mutation analysis was successfully performed on 12 primary tumours and four lymph node metastases; however, no encoding mutation was detected.


CONCLUSIONS
Contrary to reports in the literature, FIMCTs seem to have an extremely variable biological behaviour. We propose a classification based on tumour degree of differentiation and proliferative activity. These findings need to be confirmed in larger series, and exploration of further genomic regions of KIT is warranted to clarify its role in the development and progression of these neoplasms.
Department of Veterinary Medical Sciences, University of Bologna, Bologna, Italy.
Silvia
S
Sabattini
Department of Comparative Biomedicine and Food Science, University of Padua, Padua, Italy.
Mery
M
Giantin
Department of Veterinary Medical Sciences, University of Bologna, Bologna, Italy.
Adele
A
Barbanera
Department of Comparative Biomedicine and Food Science, University of Padua, Padua, Italy.
Lara
L
Zorro Shahidian
Department of Comparative Biomedicine and Food Science, University of Padua, Padua, Italy.
Mauro
M
Dacasto
Department of Comparative Biomedicine and Food Science, University of Padua, Padua, Italy.
Vanessa
V
Zancanella
IDEXX Laboratory Alfort, Alfortville, France.
Daniela
D
Prata
l'Ourcq Veterinary Clinic, Mitry Mory, France.
Eleonora
E
Trivigno
Department of Veterinary Medical Sciences, University of Bologna, Bologna, Italy giuliano.bettini@unibo.it.
Giuliano
G
Bettini
D000818:Animals; D002371:Cat Diseases / Q000201:enzymology* / Q000473:pathology*; D002415:Cats; D002454:Cell Differentiation; D004252:DNA Mutational Analysis; D007414:Intestinal Neoplasms / Q000201:enzymology / Q000473:pathology / Q000662:veterinary*; D007421:Intestine, Small / Q000201:enzymology*; D008407:Mast Cells; D009154:Mutation; D011379:Prognosis; D019009:Proto-Oncogene Proteins c-kit; D016019:Survival Analysis
D019009:Proto-Oncogene Proteins c-kit