British Journal of Radiology (2007) 80, e253-e256
© 2007 British Institute of Radiology
doi: 10.1259/bjr/21661275
Pararectal paraganglioma
S Bhatt, MD
1
S Vanderlinde, MD
1
R Farag, MD
2 and
V S Dogra, MD
1
1 Department of Imaging Sciences, University of Rochester School of Medicine, Rochester, NY, 2 Department of Pathology, Case Western Reserve University, Cleveland, OH, USA
Correspondence: Vikram S Dogra, Professor of Radiology, Department of Imaging Sciences, University of Rochester School of Medicine, 601 Elmwood Ave, Rochester, NY 14642, USA. E-mail: Vikram_Dogra{at}URMC.Rochester.edu
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Abstract
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Paragangliomas are neoplasms that arise from neural crest cells and histologically resemble their adrenal counterpart, the phaeochromocytoma. The majority of extra-adrenal tumours develop within the abdomen and are associated with the coeliac, superior and inferior mesenteric ganglia, which run parallel to the aorta. The organ of Zuckerkandl origin is most common. Pararectal paragangliomas are extremely rare. This case report presents ultrasound, magnetic resonance and histological features of such a case.
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Introduction
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Paragangliomas are rare tumours derived from neural crest cells that have the ability to secrete neuropeptides and catecholamines [1]. The majority of extra-adrenal tumours develop within the abdomen and are associated with the coeliac, superior and inferior mesenteric ganglia, which run parallel to the aorta. Common tumour locations include the organ of Zuckerkandl (close to the origin of the inferior mesenteric artery), bladder wall, heart, mediastinum and carotid and glomus jugulare bodies [2]. This case report presents an extremely rare pararectal paraganglioma including its imaging features and histopathology characteristics. This location of the tumour has been reported only once previously in the literature [3]. Of further interest is the occurrence of this tumour in pregnancy, which is a very rare association.
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Case history
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A 19-year-old female patient was found to have a suspicious right pelvic mass on ultrasound examination at 7 weeks of pregnancy. The mass was homogeneous, hypoechoic and separate from the uterus and ovary (Figure 1
). The mass was noted to be slowly growing in size and it was felt that it might interfere with normal delivery. Therefore, MR imaging of the pelvis was performed to assess the exact anatomical location of the mass. MR revealed the mass to be hyperintense on T2 weighted sequence and isointense on T1 weighted sequence (Figure 2). The mass was retroperitoneal and adjacent to the rectum, resulting in a mass effect on the cervix. Clinically, the patient gave no history of hypertension, headache or flushing that would suggest a diagnosis of a paraganglioma. Therefore, biochemical screening for paraganglioma was not considered in the management of the patient. Radionuclide studies such as imaging with iodine-131 meta-iodobenzylguanidine (MIBG) could not be carried out because of the patient's pregnancy. In view of this, at 35 weeks of pregnancy the patient underwent amniocentesis to confirm fetal lung maturity and subsequently underwent a primary low transverse Caesarean section. She also underwent an exploration of the mass, which was found to measure 7.4 cm in maximum dimension and occupy the right obturator fossa, deviating the rectum and vagina medially. The soft-tissue mass did not show any vaginal extension. The mass involved a portion of the right uterosacral ligament. It was deep to the external iliac vessels and did not involve the internal iliac artery. The mass was resected with right pelvic lymph node dissection. Histopathology confirmed the mass to be an extra-adrenal paraganglioma.
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Figure 1. Longitudinal(a) and transverse (b) grey-scale images reveal a hypoechoic well-circumscribed right adnexal mass (arrows). B, bladder; U, uterus.
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Figure 2. Axial(a) and sagittal (b) T2 weighted (FSE sequence) images demonstrate a right pararectal well-circumscribed mass (M) that demonstrates areas of increased signal. Arrowhead points to rectum. B, urinary bladder; H, fetal head.
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Discussion
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Phaeochromocytoma is a rare tumour with an estimated 800 cases diagnosed yearly in the USA, of which about 10% are extra-adrenal or paragangliomas [1]. Paragangliomas may be either sporadic or familial. Sporadic paragangliomas are multicentric in 10% of cases, whereas familial paragangliomas are multicentric in 25–50% of cases [4, 5]. In familial cases, phaeochromocytoma is a component of one of the four following autosomal dominant syndromes: multiple endocrine neoplasia Type 2 (MEN2), von Hippel–Lindau disease (VHL), hereditary paraganglioma syndrome (PGL) and neurofibromatosis Type 1 (NF1) [6]. Genetic testing in apparently sporadic cases can be beneficial, especially in patients diagnosed before 50 years of age and in those who present with bilateral, multifocal, malignant and/or extra-adrenal disease [1]. Our patient was not genetically screened.
A paraganglioma is rarely observed during pregnancy and can have potentially lethal consequences such as uncontrolled hypertension, which may increase maternal as well as fetal mortality [7–9].
Ultrasonography or MR imaging is often used to localize the tumour. The definitive treatment having the best results includes a combination procedure of surgical resection along with Caesarean section in the third trimester, preceded by medical management [10].
Paragangliomas arise from and are therefore distributed along the sites of the sympathetic ganglia from the skull base to the coccyx [11]. In total, 71% of extra-adrenal paragangliomas are located in the superior or inferior para-aortic area; they usually present as an abdominal mass producing back pain. The paraganglioma described in this case report is likely to have arisen from the pararectal region, parauterine plexus or the pelvic side wall.
The laboratory diagnosis of both phaeochromocytoma and functional paraganglioma involves the demonstration of elevated catecholamines and metanephrines in a 24 h urine collection. The measurement of plasma free metanephrine levels is also a sensitive diagnostic test [12]. Approximately 10% of paragangliomas are discovered incidentally at imaging performed to evaluate unrelated symptoms [13], as was the case in this report with the patient being evaluated for pregnancy by ultrasound, which revealed the mass in the pararectal region. Non-functional paragangliomas are rare tumours and are difficult to diagnose because of their non-secreting nature [14, 15]. A majority of extra-adrenal paragangliomas are non-functional, as in this case [16]. Therefore, clinical presentation and biochemical markers may not be contributory in making the diagnosis.
Extra-adrenal intra-abdominal paragangliomas are usually solitary, especially in adults. However, two or more separate primaries have been reported [17] as well as multiple tumours, especially along the course of the sympathetic chain [18] or distributed from the neck to the pelvis [19, 20]. The tumour usually ranges in size from 4–24 cm [21] with an average size of 10 cm [21, 22]. The gross appearance is similar to that of a phaeochromocytoma. The tumour is usually sharply circumscribed and may even appear encapsulated with a fibrous pseudocapsule. The cut surface is usually resiliently firm and grey–white but there may be areas of mottled to confluent congestion or frank haemorrhage within the tumour, which in extreme examples grossly resembles a haematoma. Central cystic degeneration can be seen, particularly in larger tumours, and can be marked [23]. The most characteristic microscopic pattern is a trabecular arrangement with anastomosing cords of tumour cells separated by a rich microvasculature. Some tumours may have a diffuse or alveolar (nesting) pattern [23]. Similar to phaeochromocytomas, there may be a remarkable degree of nuclear pleomorphism and even occasional mitotic figures [24]. Intracytoplasmic hyaline globules can be seen in some tumours [22]. Immunohistochemically, the chromaffin cells of the extra-adrenal paraganglia stain for neuroendocrine markers such as chromogranin A, and the surrounding sustentacular cells are positive for S-100 [23].
The clinical and histological distinction between benign and malignant tumours is not clear. Approximately 10% of phaeochromocytomas and 15–35% of paragangliomas are malignant. According to the World Health Organization classification of endocrine tumours, the definitive diagnosis of malignancy is based solely on the presence of metastases, characteristically to the lung, liver and lymph nodes [25].
Imaging plays a very important role pre-operatively to determine tumour localization and extent of disease. Once a phaeochromocytoma or functional paraganglioma is suspected based on symptomatology and laboratory values, MR imaging or scintigraphy can be performed to localize the tumour. MR imaging and scintigraphy are superior to CT for the localization of paragangliomas because of the superior tissue characterization, especially in cases of disease detected biochemically when the primary site is unknown [26]. Paragangliomas have low signal intensity on T1 weighted MR images and enhance strongly after administration of contrast material. They appear hyperintense on T2 weighted MR images. A speckled appearance with multiple flow voids is typical in tumours larger than 2 cm in diameter [5, 27].
Scinitigraphy using an analogue of noradrenaline (norepinephrine), MIBG, is the best study to screen for metastatic or recurrent disease because the whole body can be surveyed and then further localization of a suspected primary or metastatic site can be obtained by MRI. This scan has a specificity of almost 100% and a sensitivity approaching 90%. Subsequent targeted radionuclide therapy using MIBG may be a treatment option in some cases [28, 29]. The newest technique using fluorine-18-dihydroxyphenylalanine (18F-DOPA) positron emission tomography (PET) imaging offers even higher accuracy than MIBG scans in the localization of paragangliomas because of the higher spatial resolution of PET scanning. This imaging is based on the ability of the neuroendocrine tumour to take up, decarboxylate and store amino acids and their biogenic amines [30].
The differential diagnosis in our patient with right adnexal mass is broad and includes epithelial ovarian tumours and gastrointestinal stromal tumours (GISTs), particularly the round cell/epithelioid subtype, and metastases of carcinoma and melanoma. GISTs, the specific kit-positive mesenchymal tumours of the gastrointestinal tract, are rarely found in the anorectum and account for only 0.1% of all colorectal tumours [31]. Considering the benign nature of the mass and the clinical presentation of the patient, an ovarian tumour and GIST were the most likely choices in this case.
Other differential diagnoses include rhabdomyosarcoma, ovarian paraganglioma, leiomyosarcoma and clear cell sarcoma. Ovarian paraganglioma has been reported [32] but in our patient the ovaries were normal. Possible theories of histogenesis of primary ovarian paraganglioma include an origin from extra-adrenal paraganglia in the region of the ovary or unidirectional differentiation within a teratoma [32].
Pararectal paragangliomas are extremely rare and should be considered in the differential diagnosis of a pararectal mass. The non-functional nature of the majority of extra-adrenal paragangliomas should be kept in mind when investigating the aetiology of the mass.
Received for publication June 19, 2006.
Revision received August 14, 2006.
Accepted for publication August 21, 2006.
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Abstract
Introduction
