Hyperandrogenism from an ovarian interstitial-cell tumor in an alpaca

An 8-year-old intact female Huacaya alpaca (Lama pacos) was presented for recent development of male behavior. Serum testosterone concentration was determined to be 969.1 pg/ml by using radioimmunoassay, while the range in 33 healthy female adult intact alpacas was 11.7-62.1 pg/ml. An ovarian mass was suspected, and an exploratory laparotomy was performed. A tan mass was present on the left ovary. Histologically, the mass was composed of closely packed, plump, polygonal cells with central round nuclei with granular chromatin and abundant eosinophilic finely granular to vesiculate cytoplasm. An ovarian benign interstitial (Leydig) cell tumor was diagnosed.