Clinical History
48-year-old female patient previously treated for an early-stage breast cancer (mixed pattern: invasive ductal and medullary phenotypes). She performed local follow-up with annual mammography and ultrasound and clinical observation with laboratory tests to systemic evaluation. She had been unremarkable until she presented at our department with diffuse right flank pain.
Imaging Findings
The patient was sent for a renal ultrasound that showed a mass-like lesion surrounding the right kidney with absence of renal margins highly suggestive of renal invasion. Also, the renal lesion conditioned a certain degree of pyelocaliceal dilatation. The midline structures, namely aorta and vena cava, seemed to be spared. This was first interpreted as adrenal or renal tumour.
On non-enhanced CT a large mass involving the right kidney and right adrenal gland, somehow infiltrating the right psoas muscle ending at the upper segment of the pelvis. After IV contrast uptake, the right renal cortex was better defined as well as the same-side hydronephrosis. The lesion enhanced similarly to a solid organ and inferior vena cava encasement was assessed.
A CT biopsy was performed that confirmed breast cancer metastasis. Histology demonstrated cell proliferation morphology which was compatible with breast neoplasia with same phenotype of the primitive lesion and negative for ERBB2 and HER-2neu.
Discussion
Although the patient came with the initial diagnosis of renal/adrenal tumour we realized after the CT that the mass appeared to be retroperitoneal invading renal complex rather than the other way round. The spread along the psoas muscle, the inferior vena cava encasement with minimal aortic displacement and the obstructive effect on the same-side ureter led us to few differential diagnoses between: retroperitoneal fibrosis, retroperitoneal sarcoma, lymphoma and lastly the secondary involvement.
Retroperitoneal fibrosis usually begins near the aorta and iliac arteries, extending through the retroperitoneum to involve the ureters. It develops primarily at the level of the aortic bifurcation and goes along the common iliac arteries. Enhancement may increase 20–60 HU after contrast administration during acute phase versus no enhancement in advanced/chronic disease. [3] In our CT there is an enhancement after contrast uptake closely resembling acute retroperitoneal fibrosis. [3]
Lymphoma accounts for 33% of all retroperitoneal malignancies. At CT, presents as a well-defined homogeneous mass, with mild homogeneous contrast enhancement. The aorta and IVC can be anteriorly displaced, producing the “floating aorta” or “CT angiogram” sign. Obstruction of the ureters and IVC may be found. Few non-Hodgkin lymphomas are heterogeneous and cannot be distinguished from other primary retroperitoneal tumours on the basis of their enhancement characteristics alone. This case has all the main radiological features that favour this diagnosis. [1]
Retroperitoneal leiomyosarcomas are more commonly seen in women, 5th-6th decades of life. Histopathologically, this tumour has large areas of necrosis and cystic degeneration without calcification. This can be predominantly extravascular (62%) or intravascular (5%) in the retroperitoneum or have a combination of extra- and intravascular components (33%). Small tumours may be homogeneously solid, but large tumours have extensive areas of necrosis and occasional haemorrhage. In our case, CT findings were not accordingly to the usual aspects of leiomyosarcomas as CT showed an extensive small part mass without areas of necrotic degeneration nor visible haemorrhage.[1]
Breast cancer usually spreads metastases to the liver, lung, bone and CNS. Since there was previously diagnosed breast cancer, one should always consider secondary involvement. [3]
Gastrointestinal, gynaecological, peritoneal and retroperitoneal metastatic spread has been found to be more prevalent in lobular carcinomas. Our case was a mixed cellular phenotype that would favour an atypical metastatic spread other than the usual secondary deposits related to ductal invasive carcinomas. [4]
Imaging-guided biopsy remains the mainstay of diagnostic confirmation. [3]
Differential Diagnosis List
Retroperitoneal breast cancer metastasis
Retroperitoneal fibrosis
Lymphoma
Retroperitoneal sarcoma
Final Diagnosis
Retroperitoneal breast cancer metastasis
