Journal of Clinical Imaging 27 (2003) 426 – 430
Adrenocortical oncocytoma Case report Dario Porettia, Giovanni Mazzarolb, Guido Bonomoc, Chiara Casadiob, Massimo Bellomia,c,* a
b
Institute of Radiology, University of Milano, Milan, Italy Division of Pathology and Laboratory Medicine, European Institute of Oncology, 435, Via Ripamonti, 20141 Milan, Italy c Division of Radiology, European Institute of Oncology, 435, Via Ripamonti, 20141 Milan, Italy Received 16 October 2002
Abstract We report the case of an adrenocortical oncocytoma of the left adrenal cortex in a young woman. Physical examination revealed a mass in the left upper quadrant of the abdomen using abdomen ultrasound, computed tomography (CT) and magnetic resonance imaging (MRI), which allowed the identification of a large and inhomogeneous mass between the left kidney and the spleen. The lesion was not endowed of any specific radiologic characteristic nor bysided by any biochemical activity that could allow a radiological presurgical diagnosis. Surgical resection led to the diagnosis of adrenocortical oncocytoma, with no aspects revealing malignant potential. D 2003 Elsevier Inc. All rights reserved. Keywords: Adrenal cortex neoplasms; Adenoma, adrenal; Adenoma, oxyhilic; Magnetic resonance imaging; Tomography, X-ray computed
1. Introduction
2. Case report
Oncocytomas are neoplasms that can arise in several organs, and they are more commonly described in the kidney, salivary gland and thyroid. They consist almost exclusively of large eosinophilic and epithelioid cells, whose cytoplasm is packed with eosinophilic granulations, which correspond to numerous mitochondria as shown by electron microscopic examination. [1,2]. An oncocytoma arising in the adrenal gland is a rare finding: to our knowledge, only 21 cases have been described to date [3– 14]. In all the reported adrenal oncocytomas, a benign clinical behavior was observed, except for one case, which stood out for its local malignant behavior [4]. Nevertheless, histological findings seemed to indicate a malignant potential in a few cases, leading to a borderline and nondefinitive diagnosis of benignity [11,12]. We described a case of oncocytoma of the adrenal cortex, which presented the same imaging features as a benign neoplasm.
A 43-year-old woman with negative anamnesis complained the subtle onset of an abdominal sense of fullness. Physical examination revealed the presence of an abdominal mass in the left upper quadrant. The patient was submitted to ultrasonography (US) of the abdomen (Fig. 1) and computed tomography (CT) of abdomen and chest (Fig. 2), which showed a large irregular neoformation compressing the spleen, displacing the left kidney downwards. The mass, of inhomogeneous aspect with regular margins and probably capsulated, was well vascularised. No other lesion, nor enlarged lymph node, was detected in any adjacent organ. An adrenal origin was suspected due to the position of the lesion, but the gland could not be detected. The patient was therefore submitted to magnetic resonance imaging (MRI) (Fig. 3), which confirmed the inhomogeneous pattern of the lesion and the possible presence of a capsule, but, again, the left adrenal gland could not be identified: there were no features suggesting the invasion of surrounding structures, nor enlarged lymph nodes. No adrenal gland artery, nor superior polar renal artery, were revealed by digital subtraction angiography (DSA); the blood supply to the neoplasm appeared to derive from
* Corresponding author. Division of Radiology, European Institute of Oncology, 435, Via Ripamonti, 20141 Milan, Italy. Tel.: +39-2-5748-9041; fax: +39-2-57489040. E-mail address:
[email protected] (M. Bellomi). 0899-7071/03/$ – see front matter D 2003 Elsevier Inc. All rights reserved. doi:10.1016/S0899-7071(03)00011-1
D. Poretti et al. / Journal of Clinical Imaging 27 (2003) 426–430
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Fig. 1. Power – Doppler US imaging of the highly vascularized mass in the left abdomen showing inhomogeneous pattern with regular and welldefined margins.
branches from the splenic artery and from the left diaphragmatic artery (Fig. 4). A diagnosis of retroperitoneal neoplasm of uncertain origin was made. Due to the regular margins of the tumor, the presence of a capsule and the lack of lymph node enlargement or other organ metastases, a probable low aggressive potential was stated, despite the dimensions reached by the tumor. The patient underwent surgical resection of the neoplasm with no further diagnostic procedures, such as aspiration cytology or fine needle biopsy. At the operation, the tumor seemed to origin from the adrenal gland, which was partially distorted by the mass and closely attached to it; it did not
Fig. 3. T1-weighted coronal MRI, both before (A) and after (B) contrast medium injection, better depicts the relationships of the lesion with the adjacent organs, excluding suspected invasion. The capsule surrounding the lesion is well shown. Again, the mass is characterized by an inhomogeneous pattern, and it is impossible to identify the left adrenal gland.
Fig. 2. CT scan confirms the presence of a large mass located between the spleen and the upper pole of the left kidney. The location suggested an adrenal origin, which could not be confirmed since the gland is not detectable. The postcontrast images in the arterial phase show the presence of a rich vascularity. The irregular attenuation of the tissue is probably due to the presence of different components, or of areas of hemorrhagic infarction.
invade the surrounding structures and was actually endowed with a capsule. The neoplasm measured 14.5 cm in the major axis and weighed 550 g. It was tightly attached to a 4-cm residual adrenal gland. On cut surface, it appeared homogeneous, yellow-tan and soft (Fig. 5). On the light microscope, the neoplasm appeared as a monotonous proliferation of large pink-pale large cells, arranged in a closely packed and diffuse pattern. Clear oncocytic features were the largely abundant, fine granular cytoplasms with some vescicular nuclei with prominent
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eosinophilic nucleoli. Cells were diffusely uniform and regular in shape and in nucleo-cytoplasm ratio. Scattered mitoses (1/50 HPF) were detected, and necroses and vascular invasion were not evident. A fibrous thin layer surrounded the tumor. The diagnosis was adrenal oncocytoma, and immunohistology for vimentin, cytokeratin, Ki-67, mitochondrial antigen and CD 10 was consistent with it.
Fig. 5. Pathological specimen shows a large neoplasm with smooth surface, tan-yellow at cut, with focal hemorrhage; several vessels are recognizable within the mass.
Postoperative course was unremarkable, and the patient was discharged 7 days after surgery. No further medical therapy was administered due to the diagnosis of a benign tumor. The patient was scheduled for a follow-up program, including physical examination and US scan of the abdomen every 6 months for the first year, and each year for the following 5 years. She is still free from disease after 14 months (operated: 26/4/2001).
3. Discussion
Fig. 4. Aortic (A) and selective (B) DSA show an irregular vascular supply of the mass, arising from branches of the left diaphragmatic artery and splenic artery. No adrenal gland artery is identified; vascularity of the spleen and left kidney appears normal.
Neoplasms, composed exclusively of oncocytes, are commonly found in the kidney, thyroid, and salivary gland, but they are very rare in other sites. We identified only 21 cases of adrenocortical oncocytomas described in the literature to date [3– 14]. The average tumor size was 8.4 cm (range 3 – 15 cm), mean weight was 281 g (range 30– 865 g), mean patient’s age was 47.6 years (range 27– 72 years), 14 female and 8 male, tumor location was at the left adrenal gland in 14 cases, the right adrenal gland in 7 cases and a heterotopic location in 1 case (adjacent to the normal adrenal gland) [10]. Patients usually did not refer to the physician for symptoms related to the tumor, which was rather detected at routine investigations or owing to independent symptoms
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of other nature. One case was symptomatic: virilization in a female patient owing to hormone hyperproduction by the tumor. In another case, the infiltration of the adjacent vena cava and the liver could have caused abdominal pain. In all cases but one, the mass had a fibrous capsule and did not invade adjacent structures, nor did it give rise to distant metastases: to date, the only case of malignant adrenal oncocytic carcinoma is the one reported by ElNaggar et al. [4]. In two other cases, described by Lin et al. [11], the tumors were judged of uncertain malignant potential, on the basis of elevated Ki-67 mitotic activity, even in the absence of capsular or vascular invasion or of metastasis. The occurrence of a unilateral adrenal mass in an otherwise healthy patient opens to several differential diagnosis, either malignant or benign leading to different treatment strategies. In the reported case, the diagnosis of a metastatic malignant disease was excluded, since no primary lesion was identified by imaging work-up. Monolateral adrenal metastases without detected primary have been described as extremely rare; thus, in our case, a primitive adrenal tumor was suspected. Radiology features and biochemical evaluation ruled out the diagnosis of pheocromocytoma, which is the most frequent monolateral adrenal neoplasm, which is, however, characterized by highly vascularised tissue [15,16]. The diagnosis of nonfunctioning adenoma was considered unlikely, since these benign neoplasms are usually smaller than 5 cm [17]. Myelolipoma would have been a major hint, due to the huge size, on the presence of a capsule and on the inhomogeneous structure. Nevertheless, the absence of areas of fat-like attenuation at CT strongly argued against this hypothesis [18]. Even though primary lymphomas of the adrenals have been described as huge masses with inhomogeneous attenuation at CT [19], nodal involvement was absent and no clinical data supported this diagnosis. Adrenal carcinoma was considered in differential diagnosis. These tumors do actually reach large dimensions, but distant spread is usually present as infiltration of adjacent structures (particularly of the inferior vena carva): These were absent in our case [16]. The inability to detect the adrenal gland at CT and MRI, as well as to identify a feeding vessel from the aorta or the renal artery (such as a superior polar branch), led us to consider the possibility of a retroperitoneal soft tissue tumor. Oncocytomas very rarely affect the adrenal glands or the retroperitoneum. A specific finding of oncocytomas is the presence of a central fibrous scar, leading to a ‘‘spoke wheel’’ pattern detected by US, CT or MRI in about one third of the cases [20]: This feature was not observed in our case.
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The preoperative diagnosis was low-aggressiveness retroperitoneal tumor of unknown origin, possibly an adrenal myelolipoma with no evidence of fat. The eventual diagnosis was adrenocortical oncocytoma. Fine needle aspiration cytology could have confirmed the oncocytic nature of the tumor, and, together with radiological clinical and biochemical data, it could have led to the correct diagnosis. Nevertheless, this approach would not have changed the surgical management [21]. From a pathological point of view, no single parameter can predict clinical outcome and the assessment of malignant potential is difficult, even after surgery, and should consider multiple parameters. In conclusion, oncocytomas, although rare in this site, have to be taken into consideration while facing a differential diagnosis of tumors of the adrenal cortex. These tumors are usually benign and should be treated in a conservative way, but careful presurgery evaluation should be warranted to confirm the oncocytic nature of the lesion. Further studies are needed to clearly assess their biologic behavior.
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