Testicular intestinal-type adenocarcinoma without an identifiable extratesticular primary site: a case report and literature review.

BACKGROUND: Testicular intestinal-type adenocarcinoma is an exceedingly rare malignant neoplasm characterized by intestinal epithelial differentiation and accounts for only a minute proportion of testicular malignancies. Its imaging features remain insufficiently characterized and may overlap with those of other testicular tumors, particularly seminoma. When intestinal-type adenocarcinoma is identified in the testis, metastatic adenocarcinoma from the gastrointestinal tract or other extratesticular sites must be excluded before a definitive diagnosis can be established. CASE PRESENTATION: We report a rare case of a 33-year-old man in whom a left testicular nodule was incidentally detected during a preconception health examination. The patient had no scrotal pain, swelling, weight loss, altered bowel habits, hematochezia, or other gastrointestinal symptoms. Serum tumor markers were all within normal limits. Imaging evaluation, including ultrasonography and MRI, revealed an irregular hypoechoic nodule measuring approximately 9.7 mm, with peripheral calcifications, prominent peripheral vascularity, and peripheral rim enhancement. Histopathological examination and immunohistochemistry confirmed intestinal-type adenocarcinoma. The patient underwent left partial orchiectomy. Upper gastrointestinal endoscopy, colonoscopy, and contrast-enhanced abdominal and pelvic CT revealed no evidence of an extratesticular primary tumor. No signs of recurrence or metastasis were observed during 6 months of postoperative follow-up. CONCLUSION: Testicular intestinal-type adenocarcinoma lacks specific clinical manifestations, and serum tumor markers are usually within normal ranges. On imaging, it may present as a small intratesticular nodule with peripheral enhancement and should be differentiated from seminoma, mixed germ cell tumor, sex cord-stromal tumor, and metastatic adenocarcinoma. Through a literature review, our report provides a comprehensive summary of its multimodal imaging features, including ultrasonography, color Doppler imaging, elastography, and contrast-enhanced MRI, thereby supplementing the limited available data on this rare entity.