Bilateral renal oncocytosis with renal failure. (Letter to the Editor).

To the Editor.--The case reported by Leroy et al (1) describes an association between oncocytosis and renal failure in a patient in whom a papillary renal cell carcinoma was also present. The multiple and diffuse tumors of both kidneys caused serious involvement of the renal parenchyma, finally requiring hemodialysis. The authors concluded that although conservative management of oncocytosis is recommended, the potential association with carcinoma can benefit from different treatments, especially in patients receiving dialysis.

Oncocytomas are usually solitary, although bilateral, multifocal, and metachronous tumors have been reported, and generally they do not compromise renal function. (2) We recently observed a patient with a single renal oncocytoma presenting as a large mass involving both moieties of ectopic and crossed fused kidneys, which was associated with mild renal failure. This case presented a clinical dilemma due to the difficulty assigning a preoperative diagnosis of the tumor type and the critical anatomic location of the renal mass. For these reasons, the intra-operative risk of radical nephrectomy and consequent dialysis was very high. A review of the literature produced only 1 previous case report of renal cell carcinoma involving both crossed fused kidneys, (3) and to our knowledge, no case of oncocytoma in this setting has been described to date.

The patient was a 61-year-old man admitted for a sharp pain in the lower abdomen. Contrast-enhanced computed tomographic scan showed fused kidneys in crossed pelvic ectopia with a round renal mass greater than 5 cm in the middle parenchyma (Figure 1). Unfortunately, imaging studies presented no classic tomographic or angiographic findings. In this situation, percutaneous biopsy is the best diagnostic tool, although it is not unusual for preoperative diagnosis of oncocytoma to cause difficulty owing to problems associated with fine-needle biopsies or aspirations.

[FIGURE 1 OMITTED]

Histologic analysis of the tumor revealed no mitotic activity, hemorrhage, or necrosis. Cells were typically round to oval with abundant and eosinophilic cytoplasm. The nuclei showed minimal nuclear membrane irregularities, tiny or absent nucleoli, and only an occasional large, hyperchromatic nucleus (Figure 2, a and b).

[FIGURE 2 OMITTED]

Ultrastructural analysis showed perinuclear chromatin and abundant cytoplasm filled with mitochondria (Figure 2, c). We believe that fine-needle biopsy is useful in investigating a well-circumscribed, homogeneous mass when renal sparing surgery is not possible, as in the case reported here, or in selected patients presenting typical radiologic images of oncocytoma. In bioptic specimens, it is important to pay attention to cytoplasmic and nuclear features to distinguish between oncocytoma and chromophobe renal cell carcinoma, a distinct tumor with an intermediate prognosis. (4) The chromophobe renal cell carcinoma and the granular-subtype renal cell carcinoma are the 2 tumors that have several features that could overlap with renal oncocytoma. In difficult cases, electron microscopy and Hale colloidal iron staining may help identify chromophobe renal cell carcinoma. (5) Moreover, mixed tumors containing both oncocytic cells and chromophobe cell nets have been described recently. The chromophobe cells were in continuity with the oncocytic cells and showed specific reactivity with Hale colloidal iron staining. From these findings, an intimate relationship between these 2 renal tumors is considered possible. (6) Hale colloidal iron positivity is useful in distinguishing between oncocytoma and the eosinophilic variant of chromophobe renal cell carcinoma or for detecting the chromophobe cells in the hybrid tumors. Such tumors are generally rare, but the risk of misdiagnosis in these cases is high with the use of fine-needle specimens. Diagnosis of oncocytoma using biopsy material must be performed only in selected cases and in consideration of the cost benefit for the patient. Conservative management of oncocytomas requires strict follow-up.

References

(1.) Leroy X, Lemaitre L, De La Taille A, et al. Bilateral renal oncocytosis with renal failure: immunohistochemical and cytogenetic study of a case associated with a papillary renal cell carcinoma. Arch Pathol Lab Med. 2001;125:683-685.

(2.) Dechet CB, Bostwick DG, Blute ML, et al. Renal oncocytoma: multifocality, bilateralism, metachronous tumor development and coexistent renal cell cancer. J Urol. 1999;162:40-42.

(3.) Bolton DM, Bowsher WG, Costello AJ. Renal cell carcinoma in both moieties of crossed fused ectopia. Aust N Z J Surg. 1993;63:662-663.

(4.) Wiatrowska BA, Zakowski MF. Fine-needle aspiration biopsy of chromophobe renal cell carcinoma and oncocytoma: comparison of cytomorphologic features. Cancer. 1999;87:161-167.

(5.) Cochand-Priollet B, Molinie V, Bougaran J, et al. Renal chromophobe cell carcinoma and oncocytoma: a comparative morphologic, histochemical, and immunohistochemical study of 124 cases. Arch Pathol Lab Med. 1997; 121:1081-1086.

(6.) Noguchi S, Nagashima Y, Shuin T, et al. Renal oncocytoma containing "chromophobe" cells. Int J Urol. 1995;2:279-280.

FABIO CAMPODONICO, MD
GIORGIO CARMIGNANI, MD
Department of Urology
University of Genoa
16132 Genoa, Italy

CARLO TONCINI, MD
Division of Pathology
San Martino Hospital
16132 Genoa, Italy