Glomerular sparing pattern in primary kidney neoplasms: clinical, morphological and immunohistochemical study

Abstract

Glomerular sparing (GS) is defined as a unique growth pattern in which tumor cells replace the majority of renal tubes and overrun intact glomeruli. This phenomenon has been well recognized by pathologists as a typical infiltrative pattern and some studies suggested it was an independent risk factor. Here, we study the clinical, pathological, and immunohistochemical features of primary kidney neoplasms with glomerular sparing pattern. We searched the archives of our pathology department for nephrectomy specimens and reviewed all pathology reports from 2009-2013. We selected cases with tumor and collected clinicopathological information, focusing on re-evaluation of cases with glomerular sparing pattern. To facilitate our study we performed immunohistochemical stains of PAX-8, p63, and InI-1 on selected cases. We selected a total of 204 nephrectomy cases in this study, including 163 cases of renal cell carcinoma; 37 cases of urothelial carcinoma; 4 cases from other categories (Wilms tumor, primary diffuse large B-cell lymphoma, angiolipoma, rhabdoid tumor). Finally, we identified 7 cases of primary kidney tumors with glomerular sparing pattern: 2 cases of clear cell renal cell carcinomas (ccRCC), 1 case of collecting duct carcinoma, 2 cases of urothelial carcinoma (UC), 1 case of diffuse large B-cell lymphoma and 1 case of malignant rhabdoid tumor. The primary kidney tumors with glomerular sparing pattern are rare and incidence in our study is <4% (7/204). There is no specificity for any tumor type, but more commonly seen in high grade UC rather than RCC. It can also be seen in rare neoplasms such as collecting duct carcinoma, lymphoma and malignant rhabdoid tumor. These GS cases need to be recognized as they are often associated with high grade, high stage, large tumor size, and worse prognosis.

Keywords: Glomerular sparing pattern; clinical; immunohistochemical study; morphological; primary kidney neoplasms.

Figure 1

Renal cell carcinoma (RCC) with glomerular sparing (GS) pattern. A: Case #1, ccRCC; B: Case #2, ccRCC; C: Case #3, collecting duct carcinoma.

Figure 2

Urothelial carcinoma (UCa) with glomerular sparing (GS) pattern. A: Case #4 UCa with glandular differentiation; B: Double IHC stains of Pax8 (red) and P63 (brown); C: Case #5, UCa with extensive osteosarcomatous differentiation; D: The focal area with epithelioid features; E: IHC stain of GATA3; F: IHC stain of P63; G: IHC stain of CK5/6.

Figure 3

Diffuse large B cell lymphoma (DLBCL) with glomerular sparing (GS) pattern, case #6. A: H & E, section showed diffuse sheet growth pattern; B: IHC stain of Pax8 showed positive staining in entrapped renal tubule cells and DLBCL cells due to cross reaction of Pax5.

Figure 4

Malignant rhabdoid tumor (MRT) with glomerular sparing (GS) pattern, case #7. A: H & E, section showed similar diffuse sheet growth pattern of DLBCL in Figure 3A; B: Higher power view showed typical “rhabdoid” cytology; C: IHC stain of InI-1 showed loss of expression in MRT cells and retain expression in cells of glomerulus, vessel and stroma.