Adrenocortical Carcinoma: False Positive in an I-123 Metaiodobenzylguanedine Scan
Cristina Rodríguez Rey1 · Aída Ortega Candil1 . Eliseo Vañó Galván2 · María Nieves Cabrera Martín1 . José Luis Carreras Delgado 1
Received: 23 October 2014 / Accepted: 11 May 2015 /Published online: 3 June 2015 C Korean Society of Nuclear Medicine 2015
A 55-year-old man with a personal history of left pheo- chromocytoma 2 years previously presented with an ab- dominal mass. Tumor relapse was suspected.Abdominal ultrasound showed a large left upper quadrant solid mass (calipers), with heterogeneous echogenicity and central cystic degeneration areas or necrosis (Fig. 1a). A computed tomography (CT) scan showed surgical clips of left adrenalectomy and multiple confluent left upper quadrant masses with a maximal diameter of 19 cm and heterogeneous enhancement (Fig. 1b). Both CT scan and ultrasound images were suspicious of ad- renocortical carcinoma (ACC): size, heterogeneity and diaphragm invasion among other radiological features. Clinically, the mass grew in a few months and there were no paroxysmal hypertension episodes, nor eleva- tion of catecholamines (cathecholamine urine test: 37.2 ug/g creatinine, normal range 0.1-260).
F-18 fluorodeoxyglucose (FDG) positron emission to- mography (PET)/CT was performed as ACC was suspected
(2). ACC is an uncommon malignant neoplasm of un- known cause; however, smoking and oral contraceptives may be risk factors [1, 2]. Patients usually present with advanced-stage disease and have poor prognosis [3], with a 2-year recurrence rate that ranges from 73 to 86 % [4]. CT or magnetic resonance (MR) is most often used for initial staging of ACC and usually shows heterogeneous adrenal mass with variable enhancement of solid compo- nents [4]. F-18 FDG PET has been used successfully for detection of adrenal metastases and for staging ACC [5]. Most ACCs accumulate and retain FDG [2, 6]. However, FDG PET cannot differentiate among malignant lesions (metastases, ACC, malignant pheochromocytoma, and lym- phoma). Also, most pheochromocytomas (benign or malig- nant) are metabolically active and might accumulate FDG [7, 8]. A whole-body FDG PET scan (coronal and axial view) shows increased irregular FDG uptake in the abdom- inal masses (Fig. 2).
An I-123 metaiodobenzylguanedine (MIBG) scan was re- quested to rule out pheochromocytoma because, although conventional image methods (ultrasound and CT) and also PET/CT scan were suspicious of ACC, the primary histology of the tumor was consistent with pheochromocytoma. An MIBG scan was performed after injection of 185 MBq of I- 123 MIBG intravenously. Single photon emission tomogra- phy (SPECT)/CT scan showed abnormal isotope accumula- tion in the tumor region. The patient underwent total resection of the tumor. The histology was of ACC, with areas of necro- sis and cystic areas, so the result of the MIBG scan was a false positive. No positive chromaffin staining or chromogranin
☒ Cristina Rodríguez Rey cristina.rodriguez.rey@gmail.com
1 Department of Nuclear Medicine, Clínico San Carlos Hospital, C/Profesor Martín Lagos, 28040 Madrid, Spain
2 Department of Radiology, Clínico San Carlos Hospital, Madrid, Spain
T
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21 fps
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b
expression was found. Biopsy of the left adrenalectomy was re-evaluated from the archive and confirmed an ACC (Fig. 3).
MIBG is a guanetidine analog structurally similar to nor- epinephrine. It is recognized by type I uptake mechanism and stored in the catecholamine storage vesicles and has been used to image adrenal medulla and sympathomimetic tissues. MIBG scintigraphy has demonstrated 87 % sensitivity and 99 % specificity for detection of pheochromocytomas [8].
There are a few reports of false-positive MIBG studies. Horne et al. [9] described three cases of false-positive MIBG studies (one was an ACC). Letizia et al. [10] and Rainis et al. [11] reported another ACC with MIBG uptake. These latter au- thors divided false-positive MIBG studies into three catego- ries. The first category is neuroendocrine lesions other than pheochromocytomas (tumors of the APUD series). The sec- ond category consists in adrenal lesions other than
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pheochromocytomas (adenomas, ACC). The reasons for this abnormal uptake are unclear. The third category consists of tracer uptake adjacent to the adrenal due to abnormalities in the route of excretion.
Acknowledgments The authors declare no acknowledgments of assis- tance and were not in possession of grants or other funding for this work.
Conflict of Interest Cristina Rodríguez Rey, Aída Ortega Candil, Eliseo Vañó Galván, María Nieves Cabrera Martín and José Luis Carreras Delgado declare that they have no conflicts of interest.
Ethical Statement The authors referred this case to the President of the Ethical Committee of their Hospital prior to writing this report. She de- clared that it was not necessary to request a written informed consent from the patient because the patient had already been informed verbally that the case could be published. The President of the Ethical Committee also considered that the case accords with the 1964 Declaration of Helsinki.
Not Published Before The authors declare that the content of this man- uscript has not been published before and is not under consideration for publication anywhere else.
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