Telogen effluvium on the unilateral flank with testicular tumor in a dog

An 11-year-old intact male Miniature Dachshund was presented with localized alopecia on the right flank. Dermatological examination indicated telogen effluvium. Diagnostic imaging showed the enlargement of prostate gland, the intra-abdominal mass, and the subcutaneous cryptorchidism. An increased serum estradiol (E2) concentration and a decreased serum testosterone/E2 ratio indicated a secreting-testicular tumor. After orchiectomy and skin biopsy, a mixed Sertoli cell tumor and seminoma, with a cutaneous atrophy and telogen effluvium were diagnosed by histopathological examinations. Subsequently, decrease of serum E2 concentration and hair regrowth were observed. The present case was diagnosed as ‎sex hormone alopecia caused by excessive estrogen from a Sertoli cell tumor.