COMBINED DIAGNOSTIC APPROACHES FOR THE DIAGNOSIS OF CANINE SPLENIC NEOPLASM: CONTRAST-ENHANCED ULTRASONOGRAPHY, ULTRASOUND GUIDED CYTOLOGY, HISTOLOGY AND IMMUNOHISTOCHEMISTRY IN SELECTED LESIONS.

Focal splenic lesions are frequently identified during routine ultrasonographic examination. Differentiation between malignant and benign changes is crucial since it influence treatment and prognosis. Although B-mode ultrasound is very sensitive for the detection of splenic lesions, its specificity is low, whereas contrast enhanced ultrasound is used successfully to differentiate benign from malignant liver lesions in humans and dogs. Cytology represent another useful technique in the diagnosis of splenic disorders. However, few studies have addressed the accuracy of cytology in the evaluation of splenic lesions and specifically neoplasms. The aim of this study was to evaluate the diagnostic usefulness of contrast enhanced ultrasound and cytology in the diagnosis of splenic neoplasia, this study has been divided into a prospective and in retrospective part. The specific aim of the prospective part was to evaluate whether contrast-enhanced ultrasound can be used to more accurately characterize the perfusion of splenic focal abnormalities in small animals. Moreover, we attempted to establish diagnostic criteria useful to differentiate benign from malignant splenic lesions and to diagnose the various malignant tumors. Contrast enhanced ultrasound was performed to study focal to multifocal lesions of spleen using a second-generation microbubble contrast medium (Sonovue®) injected into the cephalic vein and enhancement patterns were described. Final diagnosis was obtained by fine needle cytology and/or histopathology after splenectomy. The aim of the retrospective study was to evaluate the role of cytology in primary and metastatic splenic tumour diagnosis using histology as the gold standard. Splenic cytological and corresponding histopathological samples obtained between 1998 and 2012 from the electronic archives of the Anatomical Pathology service of the School of Veterinary Medicine of the University of Milano, Italy. Concordance between cytology and histology was determined. Accuracy, sensibility, specificity, positive and negative predictive value of cytology for the diagnosis of splenic neoplasia was determined. Primary splenic lymphomas were collected and graded according to the WHO classification (cell size, diagnosis, mitotic index, phenotypes). A total of 26 cases of canine focal splenic masses analysed with contrast-enhanced ultrasound affected by 11 benign and 15 malignant and splenic lesions were included. In this series, most benign lesions (7/11) had a perfusion pattern similar to the adjacent parenchyma, so that the lesions were isoechoic or mildly hypoechoic. On the contrary all malignant lesions became completely or extensively hypoperfused during the wash-out phase. All hemangiosarcomas were characterized by hypoechogenicity trough all perfusion phases. Feeding vessels were present in 11/15 cases of malignancy and in 3/11 cases of benign lesions. In the retrospective study a total of 66 cases were collected. Thirty cytological samples were classified as non-neoplastic (12 true negatives, 18 false negatives compared with histopathology). Cytological diagnosis of neoplasia was obtained in 36 cases (35 true positives and 1 false positive). Cytological diagnosis was in agreement with histopathology in 71,2% (47/66) of cases. Cytology had a sensitivity of 66%, a specificity of 92%, a positive predictive value of 97%, and a negative predictive value of 40%. A comprehensive grading of 29 canine primary splenic lymphomas was performe. All cases of Marginal Zone Lymphoma (MZL), Mantle Cell Lymphoma (MCL) and follicular lymphoma with a nodular pattern of growth were of low grade. On the contrary, diffuse lymphomas were intermediate to high grade. Contrast-enhanced ultrasound can improve the characterization of focal to multifocal splenic lesions and cytology demonstrated to be a useful tool for splenic neoplasia diagnosis due to high specificity and a high positive predictive value highlighted in our study. Thus, they should be considered complementary techniques in the diagnosis of splenic lesions.