Postpubertal testicular teratoma exhibits malignant biological behavior and has metastatic potential. We report a case of a 17-year-old patient diagnosed with postpubertal testicular teratoma with massive retroperitoneal metastasis. The pathological examination revealed a mature teratoma without any other components. However, the patient had a significantly increased level of AFP, and 18F-FDG PET/CT showed the retroperitoneal metastasis had increased FDG uptake, with a SUVmax of 15.6, suggesting the coexistence of other germ cell tumor components, and the patient might have a poor prognosis. After resection of the retroperitoneal tumor, PET/CT further revealed multiple abdominal and pelvic metastases, with a SUVmax of 22.5. Therefore, the patient received a cycle of chemotherapy and follow-up PET/CT imaging showed the achievement of complete metabolic response after the treatment. In this case, PET/CT played a crucial role in detecting metastasis, compensating for the limitations of pathological sampling, thus establishing a definitive diagnosis and predicting prognosis. And it was evident that PET/CT also has the advantage of evaluating therapeutic efficacy.

RCC accounts for only 0.1%-0.3% of all kidney tumors and 2%-6% of malignant kidney tumors in children. Accounting for approximately one-third of the total number of cases in children and adolescents with RCC, Xp11.2 tRCC is the most common subtype of the MiT family translocation renal cell carcinoma, which is a group of rare childhood and adult tumors, characterized by recurrent gene rearrangements of TFE3. Here we report a rare case of a 6-year-old male patient with MiT family translocation renal cell carcinoma (MiTF tRCC) where the patient developed retroperitoneal metastasis. The patient underwent partial nephrectomy (PN), radical nephrectomy (RN), abdominal lymph node resection, and intestinal adhesion lysis. Microscopically, we detected focal and nest clump-shaped clusters of tumor cells whose cytoplasm was bright and clear. Immunohistochemistry (IHC) showed tumor cells diffusely expressed TFE3, and fluorescence in situ hybridization (FISH) demonstrated disruption of the TFE3 locus, confirming the diagnosis of Xp11.2 tRCC, the most common subtype of MiTF tRCC. Eventually, the patient obtained a good therapeutic result. This case can provide a good reference and guidance for pediatric urologists and oncologists to recognize and diagnose rare renal cell carcinoma in children.

A 50-year-old woman was referred to our hospital for elevated hepatobiliary enzymes. She had a medical history of mastectomy for left breast invasive ductal carcinoma about 10 years ago, and no apparent recurrence had been observed. Contrast-enhanced computed tomography (CT) revealed soft-tissue shadows surrounding the portal vein, celiac artery, and other vessels. The lesions involved the hilar bile duct, and the upstream bile ducts were dilated. Endoscopic retrograde cholangiography showed an obstruction in the hilar bile duct, and biopsies were taken at the site of biliary stenosis. H&E staining showed that cells with strong nuclear atypia and prominent chromatin staining infiltrated in the stroma. Immunohistochemical analysis revealed that the cells were positive for CK7, GATA3 and weakly positive for CK20. Based on these results, we made the diagnosis of biliary stenosis due to retroperitoneal metastasis from breast invasive ductal carcinoma. Biliary inside stents were placed across the biliary stricture, and she received chemotherapy plus endocrine therapy for breast cancer. So far, the partial response has been maintained for 1 year since the diagnosis of retroperitoneal metastasis. Although retroperitoneal metastasis from breast cancer, especially breast invasive ductal carcinoma, is extremely rare, it could be a differential diagnosis for biliary stenosis.

Small bowel adenocarcinoma (SBA) is rare and carries very poor prognosis if there is metastasis. This case shows the benefit of offering aggressive chemoradiation for recurrent adenocarcinoma of the jejunum with retroperitoneal metastasis to achieve the best quality of life (QoL) and potential cure. A complete response (CR) was observed following volumetric modulated arc therapy (VMAT) to biopsy-proven retroperitoneal lymph node metastasis four years after the initial diagnosis of stage pT4pN1 adenocarcinoma of the jejunum. Retroperitoneal lymph node dissection was not performed due to the excellent local control. There was no residual cancer or further metastasis seen on follow-up computed tomography (CT) imaging. The patient remains cancer free and asymptomatic eleven years after the initial diagnosis.

A 73-year-old woman was admitted to our hospital for treatment of vomiting. Four months previously, she had been diagnosed with lung adenocarcinoma (cT3N3M1a stage IVA) and started receiving afatinib as first-line treatment. On admission, the primary tumor had shrunk, but abdominal computed tomography revealed a new retroperitoneal lesion causing duodenal obstruction and hydronephrosis. She underwent gastrojejunostomy, and a biopsy of the peritoneum revealed adenocarcinoma. She was treated with second-line chemotherapy but developed cerebral infarction and died 104 days after admission. An autopsy revealed marked fibrosis with scattered tumor cells in the retroperitoneum. The underlying mechanism of the metastasis is discussed.

Radiation therapy is known to have a highly effective local and regional effect for cancer treatment; however, sporadic events of tumor regression in non-irradiated and irradiated fields have been observed over time, which is known as the \"abscopal effect.\" In this report, we describe the case of a patient with a diagnosis of unresectable advanced gastric adenocarcinoma, who developed extensive retroperitoneal lymph node involvement and did not accept management with chemotherapy. Primary radiotherapy at the local level was offered to control hemostasis, reaching an important span of complete remission of the disease.

BACKGROUND: NeuroEndocrine Neoplasms (NENs) are rare and can originate from any epithelial organ. We describe a very rare case of retroperitoneal metastasis from a non-functioning neuroendocrine tumor of the ethmoid region and focus on the various issues related to NENs, from their nosological classification up to the most recent acquisitions in the diagnostic and therapeutic field.
METHODS: A woman presented with a mass in the right retroperitoneal area that infiltrated liver and kidney. The anamnestic data showed a previous undifferentiated small cell tumor of the left ethmoid-nasal-orbital region. The mass was removed surgically and the definitive histological examination revealed a non-functioning undifferentiated malignant small cell neoplasm.
CONCLUSIONS: NENs represent a chapter of oncology whose systematization remains difficult. The lack of hormonal syndrome in Biologically Inactive Neuroendocrine Tumors (BINTs) may delay the diagnosis. Clinical manifestations relate to the size and location of the neoplasm. Small cell NeuroEndocrine Carcinoma (NEC) of the ethmoid-nose-orbital region is an extremely rare occurrence and generally the most frequent metastatic localization is represented by the larynx.
CONCLUSIONS: This case highlights the contradictions typical of NENs and only new scientific acquisitions in the histopathological field can help us in the future. Surgery remains the only possibility of treatment and diagnosis of large masses of inactive NENs. This is the only case in the world of metastasis from NEC of the nose-orbital region in the retroperitoneum.