An unusual initial presentation of lupus nephritis as a renal mass

Abstract

Lupus nephritis is a frequent manifestation of systemic lupus erythematous. Lupus nephritis usually presents with abnormal urinalysis, proteinuria, and/or renal insufficiency. We report a case of a 48-year-old woman who underwent partial nephrectomy for a fortuitously discovered solid enhancing left kidney mass. No neoplastic cells were found in the biopsy specimen; however, the pathology findings were compatible with immune complex glomerulonephritis with a predominantly membranous distribution, a pattern suggestive of lupus nephritis. The mass effect was apparently due to a dense interstitial lymphocytic infiltrate resulting in a pseudotumor. Further investigation revealed microscopic hematuria with a normal kidney function and no significant proteinuria. Antinuclear antibodies were negative, although anti-DNA and anti-SSA/Rho antibodies were positive. A diagnosis of probable silent lupus nephritis was made and the patient was followed up without immunosuppressive treatment. After two years of follow-up, she did not progress to overt disease. To our knowledge, this represents the first case of lupus nephritis with an initial presentation as a renal mass.

Figure 1

Radiologic and pathologic presentation of the renal lesion. (a) CT scan image showing a homogeneous, enhancing left renal lesion. (b) Diffusion renal magnetic resonance imaging (MRI) image of the same left renal lesion. (c) Apparent diffusion coefficient (ADC) MRI image. (d) Light microscopy with periodic acid-Schiff staining showing a lymphocytic infiltration. (e) Granular positivity of C1q on the glomerular basement membrane by immunofluorescence. (f) Higher magnification of endocapillary hypercellularity. (g) Electronic microscopy showing subepithelial deposits on the glomerular basal membrane.