Case of the Month, December 2017

Submitted by Yaniv Raphael, MD, with Thomas Learch, MD.

Presentation

22 year old male without significant past medical history presents to the Emergency Department with chief complaint of right sided back pain for the past 3 days. He describes the pain as 9/10 and waxing/waning in quality. No associated nausea, vomiting, diarrhea, fevers, chills, dysuria, hematuria, or anorexia. Vitals are within normal range. Physical examination is unremarkable. Laboratory values are notable for an elevated AST 58 [normal range 5-34 U/L], ALT 272 [normal range 0-55 U/L] and lactate dehydrogenase 464 [125-220 U/L]. Lipase is within normal range.

Imaging

A contrast enhanced CT abdomen/pelvis is ordered, demonstrating a large heterogenous retroperitoneal mass, centered in the right anterior pararenal space below the level of the renal veins. In maximal dimensions, measurements are 5.9 x 7.7 x 5.2 cm (anteroposterior by transverse by craniocaudad). The mass demonstrates avid peripheral arterial enhancement with hypo-attenuation, presumably central necrosis or cystic degeneration. There is mass effect on the adjacent viscera with superior displacement of the proximal duodenum and pancreatic head. The infra-hepatic IVC is inseparable from the mass, and may be partially invaded. A small amount of high density fluid, possibly hemorrhage, layers along the right retroperitoneum. No abdominal adenopathy or other abnormalities are identified [Figures 1-4]. The interpretation of the initial CT examination raises the possibility of a vascular mass with enhancement characteristics favoring a cavernous hemangioma.

Figures 1 & 2: Contrast enhanced CT in axial plane during arterial (Figure 1), and portal venous phases (Figure 2), demonstrating a heterogeneously enhancing right retroperitoneal mass. There is avid arterial peripheral enhancement and central degeneration or cystic necrosis. A small amount of hyper-attenuating fluid layers along the right anterior pararenal space.

Figure 1

 

Figure 2

Figures 3 & 4: Contrast enhanced CT in coronal (Figure 3) and sagittal (Figure 4) planes, demonstrating the right retroperitoneal mass, inseparable from the infra-hepatic IVC, displacing or possibly invading the vessel. Note, the vessel lumen is not expanded, and the mass is likely extrinsic to the IVC.

Figure 3

 

Figure 4

Subsequently performed MRI abdomen pelvis and MR angiogram redemonstrates the aforementioned mass with possible invasion or thrombus extension into the infra-hepatic IVC.   Note that the typical features of a soft tissue hemangioma are not supported by MRI [Figures 5 & 6]. Given the findings, the leading diagnosis of an IVC leiomyosarcoma is now considered.

Figures 5 & 6: Contrast enhanced fat-suppressed spoiled-gradient recalled echo (SPGR) T1 weighted sequences demonstrating the heterogenous mass in the right retroperitoneum in close proximity to the infrahepatic IVC. Typical features of a soft tissue hemangioma are not supposed by the MRI.

Figure 5

 

Figure 6

 At this time, the surgery oncology service is consulted, recommending an endoscopic ultrasound (EUS) with biopsy. Endoscopy demonstrates deformation and narrowing with extrinsic compression of the duodenum. A large heterogenous isoechoic mass is revealed on ultrasound, situated in the region of the right retroperitoneum, with peripheral coursing vessels and central hypo-vascularity. It is unclear whether the mass arises from or invades the infra-hepatic IVC. At this time, 2 fine needle aspirates are taken with a 22 gauge needle and sent to laboratory for cytopathologic analysis.

In further work up for metastases, a non-contrast CT chest is ordered, revealing clustered ground glass opacities in the left upper lobe, lingular segment, measuring less than 5 mm, some with halo [Figures 7 & 8]. Findings favor an infectious etiology given distribution, though follow up is recommended to exclude pulmonary metastases.

Figures 7 & 8: Non-contrast CT chest in the sagittal (Figure 7) and coronal (planes, Figure 8) demonstrates a cluster of ground glass nodules, some with peripheral halo, in the left upper lobe. Remainder of the lung parenchyma is clear.

Figure 7

 

Figure 8

 Given the overall findings and consideration for retroperitoneal malignancy, the recommendation was made by radiology to evaluate the testes as a possible source of primary malignancy. A scrotal ultrasound reveals a focal region of hyper-echogenicity in the inferoposterior right testis with posterior acoustic shadowing and no vascularity [Figure 9]. The diagnosis of a burned out (involuted) germ cell tumor is now offered as the leading diagnosis with the retroperitoneal mass thought to be a large bulky nodal metastasis.

Figure 9: Gray scale ultrasound of the right mid testis in the sagittal plane is supplemented with color Doppler interrogation and reveals a focal hyper-echogenicity in the inferoposterior testis with minimal posterior acoustic shadowing and no inherent vascularity.

Figure 9

 

Pathology later yields choriocarcinoma with positive staining for pancytokeratin, glypican-3, and beta-hCG. Tumor marker panel is negative for alpha-fetoprotein (AFP) and markedly elevated for beta-hCG < 200,000 IU/L (normal range < 1.4 IU/L).

Initially, the patient was to be treated with IVC resection and reconstruction: an extensive surgery with high peri-operative morbidity and mortality. In lieu of the scrotal mass, however, neoadjuvant chemotherapy with orchiectomy was determined to be the optimal treatment approach, conferring overall most favorable prognosis. The patient was discharged from the hospital with follow up appointments with urology and oncology.

 
Discussion

Retroperitoneal tumors in young males should be considered metastatic until proven otherwise; by far, the most common primary site is the testes. The differential of a bulky retroperitoneal mass involving or invading the IVC includes secondary involvement by renal cell, hepatocellular, or adrenocortical carcinoma—all organs that were essentially normal on the initial CT examination. Furthermore, a primary IVC leiomyosarcoma is exceedingly rare, and most commonly affects middle aged females. Primary retroperitoneal germ cell tumors are also rare, representing less than 10% of all malignant primary retroperitoneal tumors. Thus, the differential essentially is narrowed to a testicular mass.

A “burned out” germ cell tumor refers to a metastatic testicular cancer that has outstripped its blood supply and involuted, often regressing to a small calcification with little to no vascularity. However, up to 50% of burned out tumors still harbor malignant cells, and therefore, orchiectomy is still performed after neoadjuvant chemotherapy.  Also known as an “Azzopardi tumor,” the eponymous mass is named after Dr. Azzopardi, who described the phenomenon in the 1960’s after studying young patients who died of metastatic choriocarcinoma and non-seminomatous germ cell tumors. Extra-gonadal germ cell tumors are usually found in the retroperitoneum, followed by other nodal stations, including supraclavicular, axillary, mediastinal, or axillary and occasionally in the liver or lung parenchyma.

Testicular cancer represents the most common malignancy in men aged 15-35 years, and is often classified into seminomatous and non-seminomatous germ cells tumors (NGCTs). Germ cell tumors occur in young men (20-30 year olds), and are the most common subtype. Risk factors include: cryptorchidism, infertility, Klinefelter’s syndrome, and family history. Patients often present with a palpable lump, though may be occult, especially if the mass has since regressed. Tumor markers may be elevated, depending on the histologic subtype; in this case, beta-hCG and LDH were elevated, which are often associated with choriocarcinoma.

By imaging, scrotal ultrasound is modality of choice with near 100% sensitivity for detection of testicular masses. Ultrasound appearance may vary, depending on subtype. Seminomatous masses are often well defined, solid, and hypoechoic. Germ cell tumors typically are more heterogenous with ill defined borders, cystic components, and vascularity. In contrast, a burned out tumor usually reverts to a small calcification without appreciable blood flow. On MRI, testicular masses are often hypointense on T2 weighted sequences, relative to parenchyma, and enhance to variable degrees. The lymphatic drainage of the testes should also be considered. On the left, nodal drainage is to the left para-aortic station, below the level of the left renal vein, and on the right to the aortocaval station, approximately at level of L2 vertebrae— as in this case.

Primary extra-gonadal germ cell tumors are more aggressive than primary testicular cancer and also more resistant to chemotherapeutic agents. Seminomatous extra-gonadal germ cell tumors are sensitive to chemotherapy and are treated with multiple cycles of chemotherapy. On the other hand, non-seminomatous extra-gonadal germ cell tumors are frequently chemo-resistant and more aggressive with early metastases and hemorrhage, as in this case. 5 year survival rates are around 65%. Nonetheless, following chemotherapy cycle, the affected testis is often removed as to decrease risk of recurrence. 

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