Coexisting non-functioning pheochromocytoma and renal oncocytoma: a case report and review of the literature

EUROPEAN JOURNALOF

RADIOLOGY European Journal of Radiology 23 (1996) 138-142

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Coexisting non-functioning pheochromocytoma and renal oncocytoma: a case report and review of the literature G e o r g e D a s k a l o p o u l o s a, D i m i t r i o s D e l a k a s a, N i c h o l a s C h a r o u l a k i s b, N i c h o l a s G o u r t s o y i a n n i s b, A n g e l o s C r a n i d i s *a aDepartment of Urology, University General Hospital, University of Crete Medical School, PO Box 1352, Heraklion, Crete 71110, Greece bDepartment of Radiology, University General Hospital, University of Crete Medical School, Heraklion, Crete 71110, Greece

Received 20 March 1996; revision received 20 May 1996; accepted 21 May 1996

Abstract We report a case of an oncocytoma, coexisting with a non-functioning pheochromocytoma in a patient who was operated on for suspicion of a renal tumor with metastases to the ipsilateral adrenal gland. As oncocytoma is a relatively rare lesion of the kidney, estimated to account for approximately 3-5% of renal neoplasms, its coexistence with non-functioning pheochromocytoma, to the best of our knowledge, has not hitherto been described in the medical literature. Keywords: Non-functioning pheochromocytoma; Renal oncocytoma, Ultrasonography; Computed tomography (CT); Magnetic

resonance imaging (MRI)

1. Introduction In recent years much attention has been directed to the renal oncocytoma, an uncommon lesion that usually is solitary and asymptomatic [1]. Such a diagnosis may be suggested preoperatively when information from several imaging modalities is combined. However, no strict imaging criteria are available to allow the definition of the nature of the mass and its accurate distinction from other renal neoplasms [2-4]. Pheochromocytoma is a rare tumor occurring in approximately 0.1% of the hypertensive population. In some patients the single clue to its existence is a hypertensive crisis associated with pregnancy, administration of a general anaesthetic agent, surgery or use of certain drugs [5]. Postmortem series indicate that about one-third of pheochromocytomas are unsuspected clinically and that in most of these cases the tumor is responsible for a fatal outcome [61. Computed tomography (CT) and magnetic resonance imaging (MRI) are used for the non-invasive localization of these tumors [7]. Coexistence of an on-

* Corresponding author, Tel: 30 81 392340; Fax: 30 81 542066.

cocytoma with a non-functioning pheochromocytoma has not hitherto been reported. We wish to report a case of a renal oncocytoma coexisting with a non-functioning pheochromocytoma, where the preoperative diagnosis of both tumors was insufficient, due to lack of pathognomonic imaging features in both CT and MRI.

2. Case report A 71-year-old woman was admitted, with a 1 year history of non-specific gastrointestinal symptoms, including mild abdominal pain and abdominal distension. Physical examination was unrevealing. Her blood pressure was 130/80 m m H g and pulse rate 80 beats/rain. Laboratory findings were normal. Ultrasound scanning demonstrated a round, hypoechoic mass 3.5 cm in diameter, in the upper pole of the right kidney and the presence of a 2 cm hypoechoic mass in the right adrenal gland, causing compression of the inferior vena cava wall (Figs. la, lb). CT of the abdomen was carried out without administration of intravenous iodinated contrast, because of a previous history of contrast reaction, revealing two separate masses, one

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Fig. I. Ultrasonography. (a) Longitudinal scan of the right kidney shows a hypoeehoic mass 3.5 cm in diameter in the upper pole (white arrow). (b) Ultrasonography through the layer of the right adrenal gland. A hypoechoic mass 2 cm in diameter is seen, causing a focal compression of the inferior vena cava.

in the right adrenal gland which was in attachment with the posterior vena cava wall and a solid mass in the upper pole of the right kidney (Fig. 2). The density of the renal mass was similar to that of renal parenchyma. Because of the lack of contrast enhanced CT evaluation, MR imaging was performed to further define the kidney and adrenal mass. The MRI study was performed with a 0.5 Tesla superconductive magnet using the spin-echo (SE) technique. Images were obtained using a T1-

weighted sequence with a repetition time (TR) of 650 ms, an echo time (TE) of 25 ms and a T2-weighted sequence with a TR of 2800 ms and a TE of 110 ms. On SE Tl-weighted images the renal mass had a homogenous appearance with signal intensity similar to that of renal parenchyma, showing a ring-like area of low signal intensity (Fig. 3a). On SE T2-weighted images the mass had high signal intensity (Fig. 4). The adrenal mass caused focal compression of the inferior vena cava wall and appeared with low signal intensity on SE T1weighted images (Fig. 3b) and high signal intensity on SE T2-weighted images (Fig. 4). The right renal vein and the inferior vena cava were patent as demonstrated by central flow void. The renal capsule was intact and invasion of adjacent organs or adenopathy was not seen. Right partial nephrectomy was performed through a transperitoneal approach followed by a right adrenalectomy. Intraoperative frozen sections of the renal lesion were interpreted as oncocytomal. The surgical margins and regional lymph nodes were free of tumor. Histologic examination of the excised specimen revealed a right kidney oncocytoma and a pheochromocytoma of the ipsilateral adrenal gland (Fig. 5). The postoperative course of the patient was uneventful. Blood pressure and pulse rate were normal during the entire course of the hospital stay. One year after operation, a follow-up CT examination of the abdomen was normal. 3. Discussion

Fig. 2. Unenhanced CT of the abdomen. CT reveals a mass with density similar to the renal parenchyma in the upper pole of the right kidney (thin arrows) and a mass in the right adrenal in attachment with the posterior vena cava wall (thick arrows).

Renal oncocytoma is an infrequent tumor originating in the renal parenchyma with a reported incidence ranging from 3 to 5% of renal tumors and accounting for

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Fig. 4. MRI, SE T2-weighted image (TR: 2800 ms/TE: 110 ms). Both the renal tumor (arrow) and the adrenal mass (curved arrow) show high intensity signal.

Fig. 3. MRI, SE Ti-weighted image (TR: 650 ms/TE: 25 ms). (a) A tumor in the upper pole of the right kidney is shown (arrow). Signal intensity of the tumor is similar to the renal parenchyma. Note the ring-like area of low signal intensity (arrows). (b) A fight adrenal tumor of low signal intensity is shown, causing a focal compression of the inferior vena cava wail.

approximately 500 cases per year [1]. Oncocytomas are usually small, incidentally found renal tumors and less than 20% of the patients present with gross hematuria and flank pain. In our case the patient had no urological complaints and the tumor was an incidental finding because of non-specific gastrointestinal symptoms. Renal oncocytomas usually exhibit a benign clinical course and many authors have advocated partial nephrectomy or tumor enucleation [8,9]. However, preoperative or intraoperative diagnosis is a necessary prerequisite for conservative treatment of this neoplasm.

Fig. 5. Histological examination reveals a fight kidney oncocytoma (H and E x 200) (a) and a pheochromocytoma of the adrenal gland (H and E x 200) (b).

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The term pheochromocytoma is applied to tumors secreting adrenaline and noradrenaline in varying proportions. Headache, hypertension and paroxysmal attacks of palpitations, sweating, anxiety and chest pain are the most common presenting features. Hyperglycemia, glycosuria and hypercalcemia are associated metabolic disturbances. Most series report that 10-30% of pheochromocytoma cases are found at autopsy [6]. In addition, it is well documented that many patients with pheochromocytoma may be totally asymptomatic for long periods, while the effects of catecholamine release are commonly manifested by anaesthesia at surgery and in particular by the manipulation of the tumor at operation. Reports of patients who have remained asymptomatic during and following removal of unsuspected pheochromocytoma, however, are very uncommon [10]. A previous history of an uneventful operation does not exclude the diagnosis of pheochromocytoma, particularly if the procedure was performed many years previously. There are reports of intraoperative deaths due to unsuspected pheochromocytoma in patients who had successfully undergone surgery some years before [11]. Our patient had no clinical or biochemical evidence of pheochromocytoma. In addition, the fact that she underwent a major anaesthetic and significant tumor manipulation would appear to be good evidence that this was a non-functioning tumor. Attempts have been made to establish the diagnosis of renal oncocytoma preoperatively, based on radiographic findings [12,13]. The diagnosis of oncocytoma with ultrasound and nuclear medicine has been unsuccessful. Angiographic features described include a 'spokewheel' configuration of vessels, a homogenous capillary nephrogram phase and a sharp, smooth margin with a 'lucent rim' [14]. However, angiographic features are not always present, whereas, renal cell carcinomas may show any or all of these features [15]. The CT features of oncocytoma include a sharply marginated mass with a homogenous appearance on contrast-enhanced scanning [9]. These features, however are not characteristic of oncocytomas, since small renal carcinomas may exhibit identical patterns. A central, stellate scar has been reported in large oncocytomas, but this may also be seen in a renal cell carcinoma with central necrosis [3]. In our case the CT features were not conclusive, probably due to the lack of contrast enhanced studies. MRI is not more specific than other imaging techniques for the preoperative diagnosis of oncocytoma and its differentiation from renal cell carcinoma [4]. A renal homogenous mass of medium signal intensity, with a distinct margin between the tumor and the remaining kidney, vascular patency and large ring-like calcification may suggest its diagnosis [16,17]. A stellate central region of decreased signal intensity representing the cen-

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tral scar, may be additional present. Although it was initially hoped that MRI signal intensity would show differentiation between benign and malignant masses, this has not proved to be the case. The central scar, although highly suggestive of oncocytoma, is not always present and can be mimicked by areas of necrosis within a renal carcinoma [4,16]. The MRI appearance of oncocytoma in our case was shown as a homogenous mass with signal intensity similar to that of renal parenchyma on SE Tl-weighted images, without the presence of a central scar. On SE T2-weighted images the oncocytoma had high signal intensity. Because the MRI appearance of the renal mass was not that of renal cell carcinoma or oncocytoma, definitive preoperative diagnosis was not made. The patient underwent partial nephrectomy on the basis of the intraoperative frozen sections of the renal lesion, which showed oncocytoma, and not on the basis of the MRI features of the tumor. MRI features of oncocytomas described in the literature indicate that these lesions have a variable non-specific appearance [4]. The present gives further support to earlier reports indicating that the absence of a central scar should not exclude an oncocytoma from the differential diagnosis. Unsuspected adrenal masses are incidentally detected on upper abdominal CT studies in around 1% of cases [18]. CT is probably the most readily available noninvasive method of characterizing an incidental adrenal mass. Like ultrasonography, however, CT does not permit the distinction between benign and malignant lesions [18]. Recent reports have proposed the use of MRI to characterize adrenal masses and to differentiate benign adenomas from malignant lesions or pheochromocytomas [19-21]. Most malignancies and pheochromocytomas demonstrate increased signal intensity on T2-weighted images, while benign lesions demonstrate low signal intensity on both Tl-weighted and T2-weighted images [19,20]. In our case the pheochromocytoma had high signal intensity on SE T2weighted images. However, increased signal intensity in an adrenal mass on T2-weighted images is not always due to malignancy or a pheochromocytoma [22]. Additionally, there is a large number of indeterminate findings (20-30%) reported in different series of adrenal lesions, with a typical signal intensity characteristic of metastasis that was not such at biopsy [19,22]. To our knowledge, this is the first reported case of a non-functioning pheochromocytoma in coexistence with a renal oncocytoma. It is interesting to notice that the preoperative diagnosis of both tumors was insufficient, since CT and MRI could not characterize adequately these lesions. References ill Lieber MM, Tsukamoto T. Renal oncocytoma. In: deKernion JB, Pavone-Macaluso M, editors. Tumors of the Kidney. Baltimore: Williams & Wilkins, 1986; 257-273.

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