142 - Chagas Disease of the Esophagus

Editors: Shields, Thomas W.; LoCicero, Joseph; Ponn, Ronald B.; Rusch, Valerie W.

Title: General Thoracic Surgery, 6th Edition

Copyright 2005 Lippincott Williams & Wilkins

> Table of Contents > Volume II > The Mediastinum > Section XXVIII - Mediastinal Infections, Overview of Mass Lesions in the Mediastinum, and Control of Vascular Obstructing Symptomatology > Chapter 167 - Diagnostic Investigation of Mediastinal Masses

Chapter 167

Diagnostic Investigation of Mediastinal Masses

Thomas W. Shields

When a primary mediastinal mass is recognized on standard radiography of the chest in either an asymptomatic or symptomatic child or adult, the diagnostic possibilities can be narrowed to a reasonable number by considering the patient's age, location of the mass, and the associated symptoms and signs when present. Further definition of the true nature of the mass then can be established by additional noninvasive and invasive diagnostic techniques as required before a definitive decision as to therapy is made.

NONINVASIVE DIAGNOSTIC PROCEDURES

Computed Tomography

The use of computed tomography (CT) is routine and gives additional details that may not be readily discerned on standard radiography. CT is a sensitive method of distinguishing between fatty, vascular, cystic, and soft tissue masses. The differentiation of a cystic structure and a solid one, however, is not always 100% accurate. Mendelson and associates (1983) reported examples of bronchogenic cysts with high Hounsfield numbers. The high Hounsfield numbers are the result of the increased density of the contents found in some cysts. However, in most cysts, the contents are of homogeneous water density. In solid lesions, the homogeneity or inhomogeneity of the structure is usually readily apparent and may be helpful in identifying the diagnostic possibilities. Moreover, the relationship and distortion or constriction of adjacent structures such as the great vessels, trachea, and at times the esophagus caused by the mass are readily apparent. CT with contrast enhancement of the vessels is of particular importance in assessing vascular involvement in the upper areas of the mediastinum. Lastly, the use of CT is mandatory in evaluating all paravertebral masses to determine if intraspinal canal extension of the tumor has occurred whether or not standard spine radiography reveals an eroded or enlarged intervertebral foramen.

The CT scan cannot differentiate between a benign and malignant tumor, but on occasion it demonstrates invasion into adjacent structures or may reveal pleural or lung parenchymal metastases not visualized by the standard radiographs that may be present with an invasive thymoma, seminoma, or other various malignant lesions.

Magnetic Resonance Imaging

Magnetic resonance (MR) imaging may supply additional useful information in separating mediastinal tumors from vessels and bronchi, especially when the use of contrast material is contraindicated. The high signal intensity of fat and other soft tissues contrasts with the absent signal intensity of flowing blood and the low signal intensity of the surrounding lung. Furthermore, the availability of sagittal and coronal body section views with MR imaging may increase the value of this examination, as Dooms and Higgins (1986) noted. It also may be superior to CT in evaluating intraspinal extension or intrathecal spread of paravertebral masses. The moderate (gray to white) signal intensity of the T1-weighted images and the high (bright white) signal intensity of T2-weighted images also may be helpful in defining a cystic lesion that appears to be a solid lesion on a CT scan. Neuroendocrine tumors also have a high intensity on T2-weighted images.

Other Contrast Studies

Additional contrast studies (i.e., barium swallow and digital subtraction and conventional angiography) may be done in special situations, such as for the identification of the artery of Adamkiewicz in some patients with intraspinal canal extension of a paravertebral neurogenic tumor. However, in most situations, MR imaging may be used in evaluating suspected mediastinal vascular lesions instead of angiography.

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Ultrasonographic Studies

Ultrasonography is used in some institutions to determine the characteristics of a mediastinal mass (i.e., cystic or solid) and its connection or relationship with adjacent structures. An example of the former is the identification of a cervicomediastinal hygroma and of the latter is a mass contiguous with an enlarged cervical thyroid goiter. A parathyroid cyst may be suggested when a cystic structure has been identified that clinically mimics a substernal goiter. Goldberg (1973) used ultrasonography in the examination of 30 mediastinal masses and reported a 92% accuracy in its ability to differentiate among cystic, solid, and complex masses. He also found the suprasternal approach for transducer placement to be of special value in differentiating masses from aortic arch enlargements. Although the value of ultrasonographic studies is undoubted, CT scanning, MR imaging, and, when indicated, radionuclide scintigraphy have supplanted its use in many institutions. This is unfortunate, and ultrasonographic studies should remain as an important addition to our diagnostic armamentarium.

Radionuclide Scanning

Thyroid Scintigraphy

Thyroid scintigraphy with iodine 131 or 123 may be helpful in cases in which an obscure substernal or superior visceral compartment lesion cannot be distinguished as or differentiated from thyroid tissue by other means. This is particularly true in the rare cases of retroesophageal goiters. Although some investigators, such as Wright (1973) and Fraser and Par (1979), suggested that this examination is often falsely negative because of inactivity of the substernal goiter, Park and colleagues (1987) reported that the sensitivity, specificity, and accuracy of a properly performed examination were 93%, 100%, and 94%, respectively. A false-negative finding was observed in only 3 of 42 patients (7%). A sestamibi thyroid scan is also valuable in identifying the gland, a sternal extension, and even functioning thyroid tissue in the mediastinum.

Scintigraphy in the Identification of Pheochromocytoma and Other Tumors

Shapiro and co-workers (1984, 1991) reported the use of 131I-metaiodobenzylguanidine (MIBG) for the purpose of localizing biologically active paragangliomas (pheochromocytomas) in the visceral mediastinal compartment (see Chapter 191). This norepinephrine analogue, as noted by Rufini and associates (1996), is also picked up by neuroblastoma and may help delineate the extent of the disease in the mediastinum in infants and young children. Whether or not MIBG would be picked up by the neuroblastomas described by Argani and associates (1997) that occur in the anterior compartment of the mediastinum in older adults is unknown.

Other Scintigraphic Studies

Parathyroid scintigraphy with technetium 99m sestamibi to locate ectopic hyperactive parathyroid adenomas in the mediastinum is an essential study in hyperparathyroid patients and has replaced the use of thallium-technetium scintigraphy in patients in whom initial neck explorations have produced negative results. Lee and colleagues (1996) have reported that the combination of MR imaging and 99mTc sestamibi scintigraphy yields the best results. Its use in identifying functioning parathyroid cysts has been limited and has been successful in only one reported occasion by Shimizu and associates (1997).

Indium III (IIIIn-octreotide), a somatostatin analogue, has been used to identify small carcinoid tumors of the lung (see Chapter 116). Whether it will likewise locate small thymic neuroendocrine tumors is unknown at this time.

The value of [18F]fluorodeoxyglucose positron emission tomography (FDG PET) in identifying thymic epithelial tumors and thymic neuroendocrine tumors is as yet unknown. Preliminary studies by Moog and colleagues (1997) indicate that FDG PET scans may be superior to CT in revealing the extent of nodal involvement in lymphomas, both in Hodgkin's and non-Hodgkin's disease. It has even been suggested by Rodriguez (1995) and Okada (1991) and their colleagues that the degree of elevation of uptake of FDG PET is correlated to the tumor grade in non-Hodgkin's lymphoma and thus may also suggest the patient's prognosis.

Technetium 99m pertechnetate scans may be used to identify gastric mucosa in suspected neuroenteric cysts in the posterior portion of the visceral compartment. The role of radionuclide lymphoscintigraphy and the use of labeled monoclonal antibodies in the evaluation of mediastinal tumors has yet to be determined.

The use of 99mTc depreotide single-photon emission computed tomography (SPECT) in evaluating malignant mediastinal tumors is yet unreported. This compound is a somatostatin analogue receptor subtype 3, and its use to identify small malignant lesions (i.e., non small cell and small cell lung cancer) has been reviewed by Goldsmith and Kostakoglu (2000). It is possible that small thymic neuroendocrine tumors [most often of the moderately differentiated (atypical carcinoid) type] may be identified by the use of radiopharmaceuticals. Blum and associates (1999) have reported the identification of malignant carcinoid of the lung by the use of 99mTc depreotide SPECT.

DeMeester (personal communication, 1987) suggested performing gallium 67 scans to help differentiate benign from malignant anterior mediastinal masses, the uptake being infrequent in the former and common in the latter. Ferguson and associates (1987) are strong supporters of this approach. They reported little aid from the standard clinical

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evaluation of anterior mediastinal masses in determining benignity or malignancy. The gallium scan result, however, was positive in 13 of 15 patients for whom nonoperative therapy was appropriate, and was negative in seven of eight for whom excision was indicated. Nonetheless, whether this study is indicated or necessary in most instances is undetermined. It is my experience that, in most patients, the aforementioned differentiation can be based with reasonable accuracy upon the data obtained by standard evaluation of the patient. According to M ller and associates (2001), 67Ga scintigraphy is inferior in the initial evaluation of mediastinal lymphoma but does have a role in evaluating posttreatment residual disease.

Biochemical Markers

Biochemical markers and elevated hormone levels are present in patients with various mediastinal tumors. Not all patients require these studies; however, specific markers and certain hormone levels should be obtained in varying clinical settings. All young adult men with an anterior mediastinal mass, even when no symptoms or signs of malignancy are present, should have determination of the levels of -fetoprotein and -human chorionic gonadotropin. Either one or both are elevated in the presence of a nonseminomatous malignant germ cell tumor. When these levels are elevated in excess of 500 ng/mL, it is believed by many that chemotherapy may be started even without a tissue biopsy. It should be noted, however, that approximately 7% to 10% of pure seminomas may be associated with a slight elevation of the -human chorionic gonadotropin level that usually does not exceed 100 ng/mL, but an elevated level of -fetoprotein is never present.

All infants and children with a paravertebral mass should be evaluated for excessive norepinephrine and epinephrine production. This increased production is present in association with most neuroblastomas and ganglioneuroblastomas. Ferritin levels also should be obtained in these infants and children.

All patients with a suspected thymoma should be evaluated for the presence of antiacetylcholine receptor antibodies to determine whether a subclinical myasthenic state is present. Furthermore, it has been suggested that FDG PET scanning may be helpful in differentiating a noninvasive thymoma, invasive thymoma, and thymic carcinoma by the degree of uptake (i.e., minimal, moderate, or high uptake, respectively). Lastly, anterior mediastinal neuroblastomas (thymic neuroblastomas) in older adults are often associated with high levels of antidiuretic hormone, as noted by Argani and associates (1997).

Other specific markers or elevated hormone levels are discussed along with the respective causative tumors. Any of these aforementioned biochemical studies should be obtained when appropriate, but certainly not routinely.

INVASIVE BIOPSY PROCEDURES

The choice of one or more invasive diagnostic procedures depends primarily on the presence or absence of local symptomatology, location, and extent of the lesion, and presence or absence of the various tumor markers.

Generally, locally asymptomatic lesions in individuals who may or may not have an associated systemic disease, confined to the anterior compartment and with no elevated tumor markers that are present with a malignant nonseminomatous germ cell tumor, do not require tissue biopsy before removal. In fact, a biopsy of a clinically suspected stage I thymoma is to be avoided. On the other hand, if local symptoms of invasive disease are present (i.e., severe chest pain, pleural effusion, superior vena cava obstruction), a biopsy definitely is indicated.

Percutaneous Transthoracic Fine-Needle Aspiration

When it is believed that a tissue diagnosis is necessary before making a therapeutic decision, it is now the common practice to carry out a percutaneous transthoracic fine-needle aspiration of the lesion under either CT, CT fluoroscopy as suggested by Katada and colleagues (1996), or ultrasound guidance. The latter guidance is particularly useful with a suprasternal approach as noted by Wernecke and colleagues (1989). A large number of percutaneous biopsy needles are available, consisting basically of two types: (a) cutting needles that provide a core of tissue for histologic examination, and (b) fine-aspiration needles to obtain material for cytologic examination. One may use a single needle or coaxial needle in which a thinner needle is inserted through an outer needle. Various-sized needles are available, and the selection is determined by the site of the lesion and size of specimen required. Complications and contradictions of percutaneous needle biopsy are discussed in Chapters 93 and 94. At times, a core-needle biopsy may be used to obtain a larger specimen.

In patients with lesions in the anterior compartment, positive results are obtained in the vast majority with fine-needle aspiration. In fact, Bressler and Kirkham (1994) reported that positive results were obtained in 100% of such patients in their experience. Complications after fine-needle aspiration of anterior masses are rare, but Glassberg and Sussman (1990) reported two cases of life-threatening hemorrhage from injury to an internal mammary artery during a parasternal needle biopsy. Glassberg and associates (1990) subsequently presented the CT anatomic features of the internal mammary vessels so that these vessels could be more readily avoided during anterior percutaneous parasternal transthoracic fine-needle aspirations. To completely avoid these vessels, and incidentally to obtain larger specimens, Astr m and colleagues (1996) described the use of a coaxial length-matched bone biopsy system guided by CT to perform a transsternal biopsy of anterior mediastinal masses.

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These investigators reported 10 such biopsies without complication.

The percutaneous fine-needle aspiration of middle (visceral compartment) mediastinal masses can be performed transthoracically with passage of the needle through the lung or via a suprasternal approach, again guided either by ultrasonography or CT. Bressler and Kirkham (1994) reported a success rate of 75% by using various transthoracic approaches, and Belfiore and co-workers (1997) reported a success rate of 83% with the suprasternal approach. The complication rate is minimal with either approach, although a pneumothorax may occur infrequently when the lung is transversed. Hemorrhage is a rare complication.

Posterior (paravertebral) mediastinal masses are readily aspirated under CT guidance. The procedure may be facilitated by varying the patient's position as noted by Bressler and Kirkham (1994), who reported a 100% success rate in a small number of patients with lesions in this area. Biopsy of suspected paragangliomas or pheochromocytomas should be avoided because of the marked vascularity of these tumors.

When fine-needle or other aspiration techniques are unsuccessful, a more invasive surgical procedure may be required when it is essential to establish the pathologic diagnosis of a mediastinal mass.

Mediastinoscopy and Other Invasive Procedures

Anterior Compartment

The standard cervical mediastinoscopy approach is inappropriate for biopsy of tumors confined to the anterior mediastinal compartment. In this situation, tissue may be obtained by a cervical substernal extended mediastinotomy, as described by Kirschner (1991) (Chapter 161) and recently discussed by Metin and colleagues (2002) or by an anterior mediastinotomy.

Anterior Mediastinotomy

An anterior mediastinotomy has been described in Chapter 17. It is an excellent approach for the biopsy of suspected malignant invasive lesions in the anterior mediastinal compartment when a large tissue specimen is required. Its use, however, has been supplanted in most institutions by video-assisted thoracic surgery (VATS) exploration of the appropriate hemithorax.

Video-Assisted Thoracoscopy

This approach permits excellent visualization of the ipsilateral hemithorax and mediastinum. A significant amount of tissue from large, initially nonresectable masses may be obtained for definitive tissue diagnosis of such lesions as lymphomas, invasive epithelial thymic tumors (thymomas stages III and IV and type C), malignant germ cell tumors, and malignant mesenchymal tumors. Germ cell tumors that have a significant elevation of -human chorionic gonadotropin or any elevation of -fetoprotein may undergo biopsy for specific histologic diagnosis, although this is not necessary prior to institution of therapy (see Chapter 187).

Visceral Compartment of the Mediastinum

With a suspected benign or malignant lymph node process confined to the visceral compartment, biopsy via a standard cervical mediastinoscopy is used most often, although an anterior mediastinotomy occasionally is required. In the presence of a benign cystic lesion in the visceral compartment in children, a preexcisional biopsy usually is not obtained. In adults with asymptomatic cystic lesions, biopsy with aspiration via a cervical mediastinoscopy or video-assisted thoracoscopy for inferiorly located lesions can be performed, as suggested by Bolton and Shahian (1992), if no further therapy is thought necessary. If excision is contemplated, biopsy is not indicated. A cystic lesion in the anterosuperior pretracheal space that contains a clear watery fluid may be a parathyroid cyst (Chapter 197). The fluid of such a cyst should be analyzed for the presence of parathyroid hormone. When the level in the cystic fluid is elevated to a value greater than that of the serum level, the lesion is a parathyroid cyst and should be surgically removed. VATS biopsy is rarely required for lesions in the visceral compartment, although a bronchogenic cyst or a multiloculated thymic cyst may be diagnosed by this approach.

Paravertebral Sulcus

With lesions of the paravertebral sulcus areas, needle biopsy of a suspected benign lesion is not indicated. Suspiciously or frankly malignant lesions require biopsy; percutaneous needle or thoracoscopic biopsy should be performed to plan the therapeutic approach. Suspected lymphatic tumors arising in the paravertebral space, as noted by De Giacomo and associates (2000) as well as by Kelemen and Naunheim (2000), may also be an indication for a VATS biopsy approach.

Anterior Cardiophrenic Angle Masses

Lesions in the anterior cardiophrenic angle region, if cystic and shown not to arise from beneath the diaphragm, may be aspirated for both diagnosis and treatment, because most are pleuropericardial (spring water) cysts. When the mass is solid, biopsy planning depends on the presence of any local signs or symptoms, as discussed for the anterior mediastinal masses.

Other Invasive Diagnostic Procedures

Bronchoscopy, esophagoscopy, or both, may be indicated with many mediastinal masses, depending on the symptomatology, to evaluate the status and involvement of either

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structure. Rarely is tissue for diagnostic purposes obtained by either of these examinations.

REFERENCES

Argani P, Erlandson RA, Rosai J: Thymic neuroblastoma in adults: report of three cases with special emphasis on its association with the syndrome of inappropriate secretion of antidiuretic hormone. Am J Clin Pathol 108:537, 1997.

Astr m KG, Ahlstr m KH, Magnusson A: CT-guided transsternal core biopsy of anterior mediastinal masses. Radiology 199:564, 1996.

Belfiore G, et al: Middle mediastinum lesions: preliminary experience with CT-guided fine-needle aspiration biopsy with a suprasternal approach. Radiology 202:870, 1997.

Blum JE, Handmaker H, Rinne NA: The utility of a somatostatin-type receptor binding peptide radiopharmaceutical (P829) in the evaluation of solitary pulmonary nodules. Chest 115:224, 1999.

Bolton JWR, Shahian DM: Asymptomatic bronchogenic cysts: what is the best management? Ann Thorac Surg 53:1134, 1992.

Bressler EL, Kirkham JA: Mediastinal masses: alternative approaches to CT-guided needle biopsy. Radiology 191:391, 1994.

De Giacomo T, et al: Diagnostic thoracoscopy for mediastinal masses. In Yim APC, et al (eds): Minimal Access Cardiothoracic Surgery. Philadelphia: WB Saunders, 2000, p. 175.

Dooms GC, Higgins CB: The potential of magnetic resonance imaging for the evaluation of thoracic arterial diseases. J Thorac Cardiovasc Surg 92:1088, 1986.

Ferguson MK, et al: Selective operative approach for diagnosis and treatment of anterior mediastinal masses. Ann Thorac Surg 44:583, 1987.

Fraser RE, Par JAP: Diagnosis of Diseases of the Chest. Vol. 3. Philadelphia: WB Saunders, 1979.

Glassberg RM, Sussman SK: Life-threatening hemorrhage due to percutaneous transthoracic intervention: importance of the internal mammary artery. AJR 154:47, 1990.

Glassberg RM, Sussman SK, Glickstein MF: CT anatomy of the internal mammary vessels: importance in planning percutaneous transthoracic procedures. AJR 155:397, 1990.

Goldsmith SJ, Kostakoglu L: Nuclear medicine imaging of lung cancer. Radiol Clin North Am 38:511, 2000.

Goldberg BB: Mediastinal ultrasonography. J Clin Ultrasound 1:114, 1973.

Katada K, et al: Guidance with real-time CT-fluoroscopy: early clinical experience. Radiology 200:851, 1996.

Kelemen JJ III, Naunheim KS: Minimally invasive approaches to mediastinal neoplasms. Semin Thorac Cardiovasc Surg 12:301, 2000.

Kirschner PA: Cervical substernal extended mediastinoscopy. In Shields TW (ed): Mediastinal Surgery. Philadelphia: Lea & Febiger, 1991, p. 81.

Lee VS, et al: The complementary roles of fast spin-echo MR imaging and double-phase 99m Tc-sestamibi scintigraphy for localization of hyperfunctioning parathyroid glands. AJR 167:1555, 1996.

Mendelson DS, et al: Bronchogenic cysts with high CT numbers. Am J Radiol 140:463, 1983.

Metin M, et al: Extended cervical mediastinoscopy in the diagnosis of anterior mediastinal masses. Ann Thorac Surg 73:250, 2002.

Moog F, et al: Lymphoma: role of whole-body 2-deoxy-2-[F-18]-fluoro-D-glucose (FDG) PET in nodal staging. Radiology 203:795, 1997.

M ller NL, et al: Lymphoproliferative disorders and leukemia. In M ller NL, et al (eds). Radiologic Diagnosis of Diseases of the Chest. Philadelphia: WB Saunders, 2001, p. 257.

Okada J, et al: The use of FDG-PET in the detection and management of malignant lymphoma: correlation of uptake with prognosis. J Nucl Med 32:686, 1991.

Park H-M, et al: Efficacy of thyroid scintigraphy in the diagnosis of intrathoracic goiter. AJR 148:527, 1987.

Rodriguez M, et al: Predicting malignancy grade with PET in non-Hodgkin's lymphoma. J Nucl Med 36:1790, 1995.

Rufini V, et al: Iodine-123-MIBG imaging of neuroblastoma: utility of SPECT and delayed imaging. J Nucl Med 37:1464, 1996.

Shapiro B, Orringer MB, Gross MD: Mediastinal paragangliomas and pheochromocytomas. In Shields TW (ed): Mediastinal Surgery. Philadelphia: Lea & Febiger, 1991, p. 254.

Shapiro B, et al: The location of middle mediastinal pheochromocytomas. J Thorac Cardiovasc Surg 87:814, 1984.

Shimizu M, et al: Thoracoscopic resection of mediastinal parathyroid adenoma with cyst and hyperparathyroidism a case report. [Article in Japanese] Nippon Kyobu Geka Gakkai Zasshi 45:1972, 1997.

Wernecke K, et al: Mediastinal tumors: biopsy under US guidance. Radiology 172:473, 1989.

Wright FW: The Radiological Diagnosis of Lung and Mediastinal Tumors. London: Butterworth, 1973.

READING REFERENCE

Jasinski RW: CT-guided suprasternal approach for mediastinal biopsy. J Comput Assist Tomogr 16:669, 1992.



General Thoracic Surgery. Two Volume Set. 6th Edition
General Thoracic Surgery (General Thoracic Surgery (Shields)) [2 VOLUME SET]
ISBN: 0781779820
EAN: 2147483647
Year: 2004
Pages: 203

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