Telogen Effluvium on the Unilateral Flank with Testicular Tumor in a Dog

In 2019, an 11-year-old, unneutered male Miniature Dachshund was examined for localized hair loss on the right flank. The dog was diagnosed with telogen effluvium, a condition characterized by the premature shedding of hair. Further imaging tests revealed an undescended testicle, prostate enlargement, and an abdominal tumor. High levels of serum estradiol (E2) and a low testosterone/E2 ratio suggested a secretory testicular tumor. After surgical removal of the intra-abdominal testicle, histopathological examination confirmed a mixed tumor of Sertoli cells and seminoma, and skin biopsy diagnosed skin atrophy and telogen hair follicles. Post-surgery, the dog's serum E2 levels decreased and hair regrowth was observed, leading to a diagnosis of hormonal hair loss due to E2-secreting Sertoli cell tumor.