|Year : 2016 | Volume
| Issue : 2 | Page : 68-70
68Gallium-DOTANOC positron emission tomography/computed tomography scintigraphy for an unusual case of malignant pheochromocytoma: Findings and review of literature
Rajiv Yadav, Abhay Kumar
Department of Urology, Renal Transplant and Robotics, Medanta - The Medicity Hospital, Gurgaon, Haryana, India
|Date of Web Publication||15-May-2017|
Department of Urology, Renal Transplant and Robotics, Medanta - - The Medicity Hospital, Gurgaon - - 122 001, Haryana
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Functional imaging is an important step in the diagnostic approach of patients with pheochromocytoma (PCC). Metaiodobenzylguanidine (MIBG) scintigraphy (single-photon emission computed tomography) is currently the most widely used functional imaging modality for evaluating a case of PCC. However, it has some limitations and poor sensitivity, especially in cases of malignant PCC (MPCC). Positron emission tomography (PET) scanning with gallium-68 (68Ga)-DOTA-coupled somatostatin analogs is the newer upcoming modality with some superiority over MIBG scan. We present a case of MPCC with unusual invasion and metastasis positive on DOTANOC PET scan along with relevant review of literature.
Keywords: 68Gallium-DOTANOC positron emission tomography scan, malignant pheochromocytoma, metaiodobenzylguanidine scan
|How to cite this article:|
Yadav R, Kumar A. 68Gallium-DOTANOC positron emission tomography/computed tomography scintigraphy for an unusual case of malignant pheochromocytoma: Findings and review of literature. Ann Nigerian Med 2016;10:68-70
|How to cite this URL:|
Yadav R, Kumar A. 68Gallium-DOTANOC positron emission tomography/computed tomography scintigraphy for an unusual case of malignant pheochromocytoma: Findings and review of literature. Ann Nigerian Med [serial online] 2016 [cited 2020 Aug 10];10:68-70. Available from: http://www.anmjournal.com/text.asp?2016/10/2/68/206211
| Case Report|| |
A 39-year-old female patient presented with recurrent headache, vomiting, and episodic rise in blood pressure. She had undergone right side open adrenalectomy for pheochromocytoma (PCC) at another center, about 2 years before presentation. Review of presurgery computed tomographic (CT) images showed a well-defined smoothly outline, mass of size 64 mm × 66 mm in right suprarenal location with no other abnormality. Histopathology examination showed features consistent with PCC. No capsular or vascular invasion was reported. Mitotic figures were occasional. She was on follow-up with urinary metanephrines.
Current investigations showed raised urinary vanillylmandelic acid, 106.3 mg/dl (0–13.6) and metanephrines levels > 2500 μg/24 h (25–312) along with poorly defined mass lesion in suprarenal area and porta hepatis, seen on ultrasonography. Subsequent CECT [Figure 1]a,[Figure 1]b,[Figure 1]c,[Figure 1]d showed enhancing confluent lobulated mass lesions in the right suprarenal region indenting the under surface of the liver and upper pole renal cortex, extending superiorly up to the porta hepatis and under surface of right dome of diaphragm, encasing the inferior vena cava, right crus of diaphragm, and right renal vessels. The mass extends into the anterior perinephric space and the renal hilum involving the anterior pararenal fascia. Another separate, large discrete mass measuring 6 cm × 5 cm × 3.5 cm was seen indenting the right lobe of liver segment VI/VII. These findings suggested recurrent, invasive PCC.68 Gallium (68 Ga)-DOTANOC-positron emission tomography (PET) [Figure 2]a and [Figure 2]b showed large lobulated 68 Ga-DOTANOC avid soft tissue mass in right suprarenal region extending along the surface of liver and encasing the upper pole of right kidney and right renal vessels. There is absence of 68 Ga-DOTANOC avid lesion in rest of body survey. As mass was unresectable, the patient was planned for palliative chemotherapy. In view of aggressive nature of disease, urinary markers available for diagnosis, and previous histology of PCC, diagnosis of malignant PCC (MPCC) is clinically undeniable.
|Figure 1: Dynamic contrast computed tomography scan (a) noncontrast axial scan showing homogenous mass in the region of porta hepatis and renal hilum, (b) infiltrative tumor involving the porta hepatis (white arrow) along with a metastatic deposit indenting the right lobe of liver (white asterisk), (c) tumor infiltrating in retro inferior vena cava area (red arrow), (d) tumor surrounding the renal vessels (yellow arrow)|
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|Figure 2: 68Gallium-DOTANOC-PET (a) axial scan showing uptake in the infiltrative tumor corresponding to lesion seen in contrast computed tomography and (b) coronal scan showing no uptake of tracer in rest of the body|
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| Discussion|| |
Metastatic disease in PCC may present at the time of initial diagnosis or may only become evident after surgical removal of the primary tumor, usually within 5 years but sometimes 16 or more years later. Even if PCC is initially diagnosed as benign on the basis of histopathological findings, it is possible for metastasis to occur in other organs after resection. There are no definite histological or cytological criteria of malignancy. Tumor size, mitotic rate, vascular or capsular invasion are not sufficiently discriminating features to enable the differentiation of benign from malignant tumors. The initial imaging findings in benign and MPCC are nearly identical. Although extensive invasion of adjacent tissue can be considered an indicator of malignant potential, local invasiveness and malignant disease are not necessarily associated. Malignant tumor tends to be larger and weights more although this is also not a criterion. The only absolute criterion for malignancy is the presence of secondary tumor at site where chromaffin cells are not usually present and/or presence of visceral metastasis.
Nuclear imaging in combination with anatomical imaging is often required to fully delineate the extent of the disease and to choose appropriate treatment. Traditionally, metaiodobenzylguanidine (MIBG) scan is the most widely used functional imaging techniques for PCC or paragangliomas (PGL) due to its tissue specificity, good sensitivity, and world wide availability but is not without limitations. Studies indicate that MIBG scintigraphy yields poor result, especially in familiar PCC/PGL syndrome, malignant lesions (57%–77% sensitivity), extra-adrenal abdominal PGL, recurrences, and nonsecreting tumor in the head and neck region. In addition, due to its low resolution (which is prone to artifacts and attenuations), MIBG has limited ability to detect tiny lesions. In conclusion, imaging with MIBG scintigraphy has a limited role in MPCC unless it is used to determine whether or not a patient is eligible for 131 I-MIBG therapy.
The sensitivity and resolution of PET are superior to those of single-photon emission computed tomography scintigraphy. Value of somatostatin receptor (SSTR) PET imaging in MPCC was first demonstrated in year 2007 by Win et al. and later noted by many other authors. The expression of SSTR on chromaffin cells represents the rationale for the use of radiolabel somatostatin analogs in localization of these tumors. DOTA-coupled somatostatin analogs labels with 68 Ga can be used in PET imaging. At present, available three DOTA-coupled peptides such as DOTATOC (Tyr3-octreotide), DOTATATE (Tyr-octreotate), and DOTANOC (Nal3-octreotide) have excellent affinity for SSTR2 receptors (which is not always present on PCC and PGL), DOTANOC also binds specifically to SSTR3, SSTR4, and SSTR5 receptors. Recently, Kroiss et al. found that on a per patient basis, both 68 Ga-DOTATOC PET and 123 I-MIBG scintigraphy showed a sensitivity of 100% when compared with anatomical imaging. However, on a per lesion basis, the sensitivity of 68 Ga-DOTATOC was superior compared to that of 123 I-MIBG scintigraphy (99.7% vs. 63.3%, respectively). Sharma et al. found that 68 Ga-DOTANOC PET/CT shows high diagnostic accuracy and is superior to MIBG imaging in PCC with best results in MEN-2 syndrome and MPCC. Some authors have suggested that 68 Ga DOTATATE PET/CT should be considered as a first-line investigation in patients at high risk of PGL and metastatic disease. Others concluded in their study that SSTR imaging might be considered as a supplement for MIBG scintigraphy in PCC and PGL patients with suspected metastatic disease. Our patient had well-defined tumor without any capsular or vascular invasion and features of benign pheochromocytoma in the initial surgery but developed metastatic disease in follow-up. Our case highlights and emphasizes this important fact that there are no definite histological or cytologic criteria for malignant PCC, and even if pheochromocytoma is initially diagnosed as benign on the basis of histopathological findings, it is possible for metastasis to occur in other organs after resection. Therefore, the patient needs close follow-up for at least 5 years. In addition, the role of DOTANOC scan is a progress beyond the conventional usage of MIBG in such cases.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]