Primary choriocarcinoma presenting as a large pelvic mass: CT and MRI

Clinical History

A 42-year-old male presented with a 3-week history of abdominal fullness sensation. Physical examination revealed a palpable lower abdominal mass. Laboratory workup showed a white blood cell count of 9, 930 cells/mcL, elevated ESR (72 mm/hr) and LDH (472 IU/L), and high levels of &#946 ;-HCG (15, 064 mUI/mL) and AFP (1, 1 ng/mL).

Imaging Findings

Abdominal CT was initially performed, which revealed a large presacral mass extending into the pelvis between the rectum and the urinary bladder (Fig. 1). The mass appeared heterogeneous with areas of haemorrhage and mild enhancement. Pelvic MRI which followed depicted the heterogeneous nature of the mass better, with areas of necrosis and haemorrhage (Fig. 2). On contrast-enhanced T1W-images, the enhancement of the mass was more prominent (Fig. 3).
Careful sonographic examination of the testis showed no detectable lesion.
There were no other notable imaging findings, with the exception of a mild obstruction of the excretory system of the right kidney.
CT-guided biopsy was performed and histopathologic diagnosis of choriocarcinoma was made.

Discussion

Extragonadal germ cell tumours [EGGCTs] represent rare tumours arising from primordial cells misplaced during their migration to gonads.[1] They are located on the midline of the pineal gland to the coccyx. They are considered metastases from occult or regressed gonadal cancer until proven otherwise, and if a testicular tumour is detected, the extragonadal mass is always considered metastatic. Careful ultrasonography of the testes is crucial to determine whether the germ cell tumour is metastatic gonadal or extragonadal.

Histologically, EGGCTs are divided into seminomas and nonseminomatous tumours, which usually have a more aggressive behavior. Nonseminomatous germ cell tumours [NSGCTs] include teratoma, embryonal carcinoma, yolk sac tumours, choriocarcinoma and tumours with mixed histology.

Nonseminomatous GCTs appear as large heterogeneous masses with areas of necrosis, haemorrhage, or cystic degeneration. On MRI, the cystic and necrotic areas appear hyperintense on T2WI. T1-hyperintensities are seen in more than 50% of cases corresponding to areas of haemorrhage. Fat and calcifications are hallmarks of teratomas, most of which are benign. These imaging characteristics reflect the pathologic features of each tumour, and histologically similar GCTs at varying sites have similar radiologic features.[2]

EGGCTs can be found anywhere on the midline, particularly the mediastinum, the retroperitoneum, the sacrococcyx, and the pineal gland. Other less common sites include the orbit, suprasellar area, palate, thyroid, submandibular region, anterior abdominal wall, stomach, liver, vagina, and prostate.[2]

The vast majority of sacrococcygeal GCTs are teratomas. Malignant GCTs in the presacral area are extremely rare.[3] A classification system for the morphologic features of sacrococcygeal GCTs has been developed by the Surgical Section of the American Academy of Pediatrics; type I tumours are predominantly external; type II tumours are dumbbell shaped, with significant external and intrapelvic components; type III tumours have small external component; and type IV tumours are entirely internal without an external component. The prevalence of malignancy is lowest in those sacrococcygeal tumours with a large external component and highest in those located predominantly or totally within the presacral region.

Lesions with a significant presacral component cause anterior displacement of the rectum and urinary bladder. The imaging approach to the evaluation of presacral lesions is not standardised. Imaging is usually complementary between CT and MRI. Markedly increased β-HCG is usually associated with choriocarcinoma.

The initial treatment of all sacrococcygeal germ cell tumours is surgical excision followed by chemotherapy and radiation therapy.

Differential Diagnosis List

Final Diagnosis

Extragonadal choriocarcinoma of the presacral space

URL:	https://eurorad.org/case/14885
DOI:	10.1594/EURORAD/CASE.14885
ISSN:	1563-4086