Primary Renal Lymphoma (PRL) is a debated disease as the kidney is a non-lymphoid organ. Very few cases that fulfill the diagnostic criteria have been reported. We report a middle aged female patient with PRL who presented with large renal mass.

A 52-year-old female presented with complaints of fever, loss of appetite and generalised weakness of 4 months duration. There was no history of pain abdomen, jaundice, bowel or urinary disturbances.

She was diagnosed by a general practitioner as Pyonephrosis based on ultrasonogram of abdomen report suggestive of grossly enlarged left kidney. As the symptoms did not subside with medical treatment, she was referred to Department of Surgical Oncology, Wockhard-Fortis Hospital and Cancer Institute, Mulund. On evaluation, systemic examination was unremarkable. On abdominal palpation, there was mass in left hypochondrium and lumbar region 10x14 cm, non-tender and bimanually palpable. Hematological and biochemical investigations were within normal limits, except for raised lactate dehydrogenase (LDH) being 1,224 U (normal range: 313–618 U).

Abdominal ultrasound showed enlarged left kidney with associated large perinephric collection. Abdominal computerised tomogram (CT) scan showed large left renal fossa and pelvic retroperitoneal mass lesion, extending into left pelvic retroperitoneal tissues and left perinephric space. There was invasion of psoas muscle posteriorly, and bladder base inferiorly. Diethyl triamine penta-acetic scan revealed completely non-functional left kidney.

As the imaging was atypical and LDH levels were raised, renal biopsy was performed. Biopsy report was suggestive of malignant small round cell tumour (Figure 1). Immunohistochemical analysis was suggestive of non-Hodgkin's lymphoma (NHL) - diffuse large B-cell phenotype. (NHL of diffuse large B-cell phenotype positive for CD 20. Negative for CD3 and CD5.Mib-1 labeling index - approximately 80%).

Based on the diagnosis, she was given the standard R-CHOP chemotherapy (Rituximab, Cyclophosphamide, Doxorubicin, Vincristine, Prednisolone), as for other NHL, she was under remission after six cycles, but after six cycles she was lost on follow-up.

PRL is a questionable entity, and mere existence of lymphoma as a primary pathology was questioned as kidney is not a lymphoid organ. Renal involvement is common with systemic lymphoma and in autopsy series, estimates of renal involvement in patients with known lymphoma range from 30 to 60percent, especially with high-grade NHL.¹

Primary involvement of kidney is extremely rare, and defined as kidney being only organ involved, without systemic spread, or as a presenting organ and accounts for <1% of all renal masses.² It is believed by some investigators that lymphomas in nonlymphoid organs, e.g., kidney arise in the setting of an inflammatory disease with a lymphoplasmacytic infiltrate. The proposed pathogenetic mechanisms of PRL include: origin in the subcapsular lymphatics, seeding via hematogenous route, an extension from retroperitoneal disease or inflammatory disease with a lymphoplasmacytic infiltrate.³

Clinically, PRL has diverse presentations and include: flank pain, hematuria, palpable mass, fever, weight loss, and fatigue, B symptoms of lymphoma, progressive renal failure. Slight male preponderance is seen and average age of diagnosis is above 60 years of age.⁴ The symptoms observed during the later stages are lumbalgia, hematuria and fever. However, in the series studied by Dimopoulos et al., all six patients presented symptoms related to the involvement of the urinary tract and the absence of peripheral palpable lymph nodes.⁵

Clinico-radiologically it is often misdiagnosed as renal carcinoma. CT is the imaging modality of choice in patients with suspected renal masses including renal lymphoma and also for definition of extra-renal extent of disease. The typical CT patterns in renal lymphoma include: multiple renal masses, solitary masses, renal invasion from contiguous retroperitoneal disease, perirenal disease or diffuse renal infiltration.⁶ The differentiating features (vs renal carcinoma) include absence of calcification, post contrast homogenous attenuation, absence of renal vein thrombus and absence of a mass effect on renal vessels and pelvicalyceal system in PRL.⁷

Renal biopsy is essential for pre-operative diagnosis. Many classes of NHL, including large, small, intermediate and mixed cell types with high, intermediate or low grade histologies, have been described. The neoplastic lymphoid cells may express both B- and T-immunoblastic phenoltypes. The most common histological subtype encountered is diffuse large B-cell lymphoma. Rare subtypes are follicular lymphoma, small non-cleaved non-Burkitts lymphoma and MALToma.⁸

Patients with atypical features of renal cell carcinoma should undergo a preoperative percutaneous renal biopsy. The sensitivity and specificity of renal biopsy are 70% to 92% and 100%, respectively, with accuracy close to 90%.⁹

Standard management of a renal mass is nephrectomy. PRL is a rare exception in which patient should be treated first with chemotherapy and prognosis is poor with median survival less than a year. The dismal prognosis can be improved with the addition of Rituximab to the conventional CHOP regimen. An early pre-operative diagnosis and institution of chemotherapy can help to improve outcome in these patients.

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