Interesting case of a large renal mass

Clinical History

A 68 year old lady presented with weight loss. Ultrasound of the abdomen was performed as part of the initial work up which revealed a large renal mass.

Imaging Findings

This patient presented with a history of weight loss. Clinical examination was unremarkable. Patient was investigated for the underlying cause. Blood tests were unremarkable apart from low haemoglobin of 8.9 g/dl.
Initial imaging included CXR (normal) and US (Fig. 1), which revealed grossly abnormal left kidney with a large renal mass. It was enlarged with distortion of the normal architecture. Renal vessels appeared partially compromised. CT staging (Fig. 2) was performed for further evaluation. This revealed a large infiltrative lesion involving the whole of the left kidney, extending into the retroperitoneum. Renal vessels appeared compressed but patent. No chest or mediastinal disease was seen. PET images demonstrated moderate avidity lesion in the left kidney. No extension of this was seen above the diaphragm. No other abnormal uptake was seen in the abdomen or chest. Based on the image findings, which revealed a very homogeneous lesion with relatively preserved anatomy; lymphoma was considered as first diagnosis. The differential of primary renal cancer was considered.
CT guided biopsy was then performed. Histopathology results confirmed a high-grade large B cell lymphoma with positive immunohistochemistry for lymphoma. After review by oncologist, she received 4 cycles of chemotherapy. Post chemotherapy scan (performed with multislice scanner) at 2 months showed significant reduction in the size of the lesion. The left kidney demonstrated better uptake of contrast when compared to the previous scan. This patient is currently under regular review by an oncologist.

Discussion

Lymphoma is a cancer that begins in the lymphatic cells of the immune system and presents as a solid tumor of lymphoid cells. There are two main types of lymphomas: non-Hodgkin’s lymphoma and Hodgkin’s lymphoma. About 80% of all lymphomas diagnosed are non-Hodgkin’s lymphoma. The causes of both types of lymphoma are still unknown. Non-Hodgkin's lymphoma is the most common type of lymphoma. Diffuse large B-cell lymphoma is a common type of non-Hodgkin lymphoma, accounting for about 2 in 5 of all cases.
Primary lymphoma of the kidney is extremely rare; most lymphomatous renal masses represent extension from adjacent sites of disease or involvement by generalized disease [1]. Renal lymphomas are predominantly large-cell lymphomas of B-lineage affecting middle-aged and older adults and often can be treated successfully. Both clinically and pathologically, they can be mistaken for carcinomas of the kidney [2].

Plain radiographs are of limited use. Ultrasound may identify a renal mass. However, on ultrasound, the parenchymal masses are often hypoechoic, reflecting tissue homogeneity, and they can be misidentified as renal cysts. Intravenous urography may show non-specific distortion of the collecting system, however, it can demonstrate normal or near-normal findings in renal lymphoma. Regarding nuclear medicine studies, although gallium-67 citrate is an isotope that often accumulates in lymphomatous tissue, it can also be taken up by inflammatory masses. Nonenhanced CT scan studies or MRIs can cause masses to be missed, particularly when such masses are small. Contrast enhanced CT scanning is the diagnostic modality of choice in patients with suspected renal masses. It can depict renal involvement in most patients with lymphoma, define the extent of disease and help in staging. Typical imaging findings of renal lymphoma include multiple poorly enhancing masses, retroperitoneal tumors that directly invade the kidneys, a solitary mass, bilateral renal enlargement, and perirenal soft-tissue masses. Although the masses are often homogeneous on CT scans, they can be heterogeneous or low density, as well as mimic a complicated cyst. This is typically a sign of tumor necrosis in patients undergoing chemotherapy. In approximately 50% of patients, associated retroperitoneal adenopathy is noted. Continuous retroperitoneal extension into the kidney is a common pattern of renal involvement in lymphoma and is seen in approximately 30% of patients [3]. Differentials include renal cell carcinoma, metastatic disease, angiomyolipoma and renal abscess.

Chemotherapy is the main treatment for diffuse large B-cell lymphoma. Chemotherapy will lead to a cure in a large number of people with diffuse large B-cell lymphoma. Even when a cure is not possible, treatment can still usually control the disease for a number of years.

Differential Diagnosis List

Final Diagnosis

High grade large B cell lymphoma

URL:	https://www.eurorad.org/case/8595
DOI:	10.1594/EURORAD/CASE.8595
ISSN:	1563-4086