Regressed Seminoma with Metastases to the Jejunum and Retroperitoneum.

A 66-year-old man with vomiting and weight loss was referred to our hospital. Abdominal computed tomography showed small bowel obstruction caused by a presumed small intestinal tumor. Single-balloon endoscopy showed an ulcerated tumor and marked stenosis of the jejunum. Immunohistochemical staining suggested the tumor to be poorly differentiated or undifferentiated carcinoma. The patient underwent open surgical resection of the jejunal tumor and regional lymph nodes both to improve the quality of life of the patient and to possibly get a cure of the presumed jejunal carcinoma. Pathological examination of the excised tumor and lymph nodes including para-aortic lymph nodes showed large-sized tumor cells and massive lymphocyte infiltrates. Immunostaining showed the tumor cells to be OCT3/4, AE1/AE3, CD117, and D2-40 positive, leading to the diagnosis of metastatic seminoma. With the preoperative diagnosis of a presumed burned-out tumor of the testis, the patient underwent left high orchiectomy. Pathological examination of the left testis showed marked scar tissue, no teratoma elements, and no residual tumor cells. Under the final diagnosis of regressed seminoma, the patient has received combination chemotherapy using bleomycin, etoposide, and cisplatin as adjuvant chemotherapy. Surgical oncologists should take regressed seminoma into their differential diagnosis when the biopsy specimens of the presumed intestinal malignancy show poorly differentiated or undifferentiated atypical cells with massive lymphocyte infiltrates, especially in postpubertal men. Confirmation of a malignant noninvasive component should be another important clue to the appropriate differential diagnosis when choosing between metastatic seminoma and poorly differentiated or undifferentiated intestinal primary malignancies.