Koi carp presenting with coelomatic neoplastic lesions are of growing importance in Switzerland and elsewhere in Europe, as clinical diagnosis is usually difficult and prognosis is usually poor because of late recognition. To gain more information about this condition, between 2008 and 2012, 117 koi diagnosed with coelomatic tumours were included in this study. The nature and growth characteristics of these pathologic tissues were documented. Out of 117 koi, 48.9% (n = 57) were female; the ovary was the most often affected organ (35%, n = 41), and in 62.4% (n =73) of cases, the cells of origin were identified as stromal cells of the sex-cord and the tumours were identified as sex-cord stromal tumours. The characteristics of growth and histology showed that the majority of tumours were malignant.KEY WORDS: Koi carp · Neoplasm · Histopathology · Ovary · Testis · Sex-cord stromal tumour
Resale or republication not permitted without written consent of the publisherDis Aquat Org 119: [219][220][221][222][223][224][225][226][227][228][229] 2016 To gain more information about the nature of neoplastic lesions in internal organs and the pathological features of these neoplasms, koi presenting with various abdominal neoplasms were examined between 2008 and 2012. Specifically, possible sex-specific differences, the organs affected, the tissue/cells of origin and the characteristics of neoplastic growth were investigated.
MATERIALS AND METHODS
Origin of samplesBetween 2008 and 2012, all koi carp with an enlarged abdomen, which were euthanized or died in our veterinary clinic, were examined pathologically. A standard necropsy was performed. Those fish showing a coelomatic mass suspected to be a tumour were included in this study, for a total of 117 animals. As there was no recurrence of tumour masses in the same animal, 1 tumour case always corresponds to 1 animal. If possible, the sex of the affected animal was recorded. Macroscopic changes of internal organs, including extent and appearance of the coelomatic mass (colour, surface, cut section and texture) were recorded in 62 cases. In all 117 cases, tissue samples of different representative areas were fixed and stored in 10% buffered formalin and sent for analysis to the Centre for Fish and Wildlife Health (University of Bern). These samples were identified histologically as coelomatic neoplastic lesions. This criterion was used for the final decision to include the animals in this study.
Histopathology and immunohistochemistry (IHC)Formalin-fixed samples were paraffin-embedded and routinely processed. Three or 4 serial sections were prepared: the first sections were stained with haematoxylin-eosin (H&E), the remaining sections were used for IHC staining.As a basis to classify the neoplasms, criteria defined in the World Health Organization classifications for tumours in domestic animals (Kennedy et al. 1998, Head et al. 2003, Meuten et al. 2007) were used.Because of limited availability of antibodies working properly on our koi carp tissue, only an epithelia...
