Frequency and histologic characterization of coelomatic neoplasms in koi Cyprinus carpio koi

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.