Dear Editor, I read with great interest the recent publication by Mehta et al. [1] on 15 cases of primary benign vascular tumors and tumor-like lesions of the kidney. As the authors mention, these lesions can sometimes raise suspicion for or be associated with a malignancy. In this context, I would like to insist on the importance of differential diagnosis between these benign vascular tumors and several renal tumors exhibiting an arborizing capillary network. The two biopsy cases of renal vascular lesions sent to me for consultation will illustrate the issue. In the original pathology reports, the two lesions were diagnosed respectively as renal capillary hemangioma and arteriovenous malformation after examination of the H&E slides and the immunohistochemical stains for CD10, AE1-AE3, EMA, SMA, and CD34 for the first case (Fig. 1), and for AE1-AE3, SMA, and CD34 for the second case. After reviewing all slides and performed additional immunohistochemical stains for CAIX, CD10 (for the second case), CK7, protein S100, α-inhibin, and NSE, I reclassified these two lesions as primary hemangioblastoma of the kidney. Hemangioblastoma is a rare and benign lesion of uncertain histogenesis, i.e. the embryological origin of the stromal cells, the principal cell of this lesion, remains uncertain. Owing to its rare occurrence in kidney, which makes it an unexpected diagnosis in this organ, primary hemangioblastoma of the kidney is under diagnosed and might be diagnosed as a clear cell renal cell carcinoma (ccRCC) [2]. Nevertheless, as underlines it the two biopsic cases, hemangioblastoma can be also misinterpreted as hemangioma or arteriovenous malformation. In these cases, the capillary network was prominent whereas stromal cells, the key element of the diagnosis, were irregularly scattered in a loose and oedematous or fibrous stroma and exhibited occasional lipid droplets (Fig. 1). In an earlier published case, an extraneural hemangioblastoma was also regarded as a lobular capillary hemangioma [2]. Furthermore, ccRCC needs to be considered before a diagnosis of benign renal vascular tumor can be made. This is particularly true in ccRCC with significant degenerative changes resulting in rare and indistinct clear cells. As this “evanescent” pattern is generally focal in ccRCC, this differential diagnosis is really difficult on needle core biopsies, such as the case presented in Fig. 1. Also in clear cell papillary renal cell carcinoma [3] an “evanescent” pattern (Fig. 1) can be observed. To adequately appreciate these “nonvascular” differential diagnoses additional immunohistochemical studies are necessary, not limited to vascular (CD34, CD31, factor VIII), muscular (SMA, MSA) and melanocytic (HMB 45, Melan-A) markers. Pan-cytokeratin staining using the AE1–AE3 antibody, which is often performed, is not adequate to reject a diagnosis of ccRCC or hemangioblastoma since it is positive in only 35 % of ccRCC [4], and negative in hemangioblastoma [2]. As a consequence, to exclude ccRCC in particular on needle core biopsies, immunohistochemical stainsmust include CD10, CK7, and CAIX. The latter is frequently most helpful in this context with its diffuse and intense membranous staining in contrast to CD10 which tends to be weaker and focal. For ccpRCC, the same three markers can support the correct diagnosis. Of note, these three markers are included in the immunohistochemical marker panel proposed by Al-Ahmadie et al. J. Verine Universite Paris Diderot, Sorbonne Paris Cite, Laboratoire de Pathologie, UMR-S 728 Paris, France
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Jan 1, 2014
Murat Ustuner + 6
Open Access
