Adult intratesticular splenogonadal fusion simulating testicular cancer: a diagnostic blind spot in modern urologic oncology

Splenogonadal fusion (SGF) remains one of the rarest and most diagnostically deceptive causes of scrotal pathology, frequently mimicking the clinical and imaging features of testicular malignancy despite its benign histology. Its exceptional rarity in adults, combined with the absence of reliable noninvasive preoperative diagnostic criteria, creates a major challenge in urologic practice, often necessitating management driven by concern for cancer. We present a 29-year-old man with a symptomatic left testicular mass and imaging highly suspicious for malignancy, prompting radical inguinal orchiectomy after standard evaluation could not confidently exclude a testicular neoplasm. Unexpectedly, final histopathology demonstrated ectopic splenic tissue consistent with SGF without evidence of germ cell tumour or other malignancy. This case highlights the persistent gap between preoperative suspicion and definitive diagnosis, emphasizing the importance of recognizing rare benign entities that closely imitate testicular cancer and may still lead to radical surgery in otherwise healthy young adults unnecessarily.