Bone marrow toxicity induced by hyperestrogenism syndrome in a labrador secondary to Sertoli cell tumour

Abstract The present case describes bone marrow toxicity (myelotoxicity) in an 8‐year‐old unilateral cryptorchid labrador diagnosed with a Sertoli cell tumour. The dog exhibited severe pancytopenia, feminisation and systemic complications secondary to hyperoestrogenism. With surgical removal of the tumour and aggressive supportive care allowing haematopoietic recovery, the prognosis remained favourable. This report highlights the pathophysiology, diagnostic challenges and treatment strategies. It emphasises the importance of early detection and timely intervention to improve clinical outcomes.