Fat attenuation lesions of the mediastinum.

The identification of fat within a focal or diffuse mediastinal lesion significantly narrows the differential diagnosis. In many cases, a specific diagnosis can be suggested on the basis of CT findings. In this article, we illustrate and review the characteristic CT features of common and uncommon fat attenuation lesions of the mediastinum, including focal masses and diffuse abnormalities.

Fibrosing mediastinitis.

Fibrosing mediastinitis is a rare benign disorder caused by proliferation of acellular collagen and fibrous tissue within the mediastinum. Although many cases are idiopathic, many (and perhaps most) cases in the United States are thought to be caused by an abnormal immunologic response to Histoplasma capsulatum infection. Affected patients are typically young and present with signs and symptoms of obstruction or compression of the superior vena cava, pulmonary veins or arteries, central airways, or esophagus. There may be two types of fibrosing mediastinitis: focal and diffuse. The focal type usually manifests on computed tomographic (CT) or magnetic resonance (MR) images as a localized, calcified mass in the paratracheal or subcarinal regions of the mediastinum or in the pulmonary hila. The diffuse type manifests on CT or MR images as a diffusely infiltrating, often noncalcified mass that affects multiple mediastinal compartments. CT and MR imaging play a vital role in the diagnosis and management of fibrosing mediastinitis.

Bronchogenic cyst: imaging features with clinical and histopathologic correlation.

PURPOSE: To characterize the imaging features of bronchogenic cysts. MATERIALS AND METHODS: The computed tomographic (CT) and/or magnetic resonance (MR) or ultrasonographic images in 68 histopathologically proved cases of bronchogenic cyst in 38 male and 30 female patients, aged newborn to 72 years (mean, 22 years), were retrospectively reviewed. RESULTS: There were 58 mediastinal and 10 extramediastinal cysts. At CT (n = 62), 60 cysts were sharply marginated with smooth (n = 35) or lobulated (n = 25) borders. Twenty-five cysts were of water attenuation, 25 were of soft-tissue attenuation, two were air filled, two had an air-fluid level, and two had dependent milk of calcium. On T1-weighted MR images (n = 23), 18 cysts were hyperintense and five were isointense to cerebrospinal fluid. On T2-weighted MR images (n = 18), 17 cysts were isointense or hyperintense to cerebrospinal fluid. Of the 25 soft-tissue-attenuation lesions at CT, 11 appeared cystic because of internal homogeneity, lack of internal enhancement, mural enhancement, and characteristic location. Fourteen appeared solid based on morphology and attenuation. MR imaging of nine of the latter showed marked hyperintensity on T2-weighted images. CONCLUSION: CT of bronchogenic cysts typically shows sharply marginated mediastinal masses of soft-tissue or water attenuation. Most appear cystic. A minority appear solid and can be confused with other lesions; MR imaging can be useful for elucidating the cystic nature of these lesions.

Primary cardiac and pericardial neoplasms: radiologic-pathologic correlation.

Primary cardiac and pericardial neoplasms are rare lesions and include both benign and malignant histologic types. Myxoma is the most frequent primary cardiac neoplasm, but other benign tumors include papillary fibroelastoma, rhabdomyoma, fibroma, hemangioma, lipoma, and paraganglioma. Cardiac sarcoma represents the second most common primary cardiac neoplasm. Lymphoma can also affect the heart primarily. Pericardial tumors that affect the heart include benign teratomas and malignant mesotheliomas. Patients affected with cardiac or pericardial neoplasms often present with cardiovascular compromise or embolic phenomena and exhibit cardiomegaly at chest radiography. Benign cardiac tumors typically manifest as intracavitary, mural, or epicardial focal masses, whereas malignant tumors demonstrate invasive features and may involve the heart diffusely. Benign lesions can usually be successfully excised, but patients with malignant lesions have an extremely poor prognosis.

Pulmonary pathology of Erdheim-Chester disease.

Erdheim-Chester disease (ECD) is a rare non-Langerhans' cell histiocytosis that may present with pulmonary symptoms. The condition seems to be nonfamilial and typically affects middle-aged adults. Radiographic and pathologic changes in the long bones are diagnostic, but patients often present with extraskeletal manifestations. Advanced pulmonary lesions are associated with extensive fibrosis that may lead to cardiorespiratory failure. The clinical, radiologic, and pathologic features of six patients with ECD with lung involvement are presented. The patients were three men and three women (mean age, 57). Five presented with progressive dyspnea, and one presented with diabetes insipidus. Open-lung biopsies showed histiocytic infiltrates in a lymphangitic pattern with associated fibrosis and lymphoplasmacytic inflammatory infiltrates. The histiocytes did not stain with periodic acid-Schiff. Immunoperoxidase studies performed on specimens from five of six patients showed that the histiocytes were positive for CD68 and Factor XIIIa and negative for CD1a. Specimens from two patients exhibited immunoreactivity for S-100 protein. Electron microscopy studies performed on specimens from two patients showed phagocytic lysosomes but no Birbeck granules. Clinical follow-up of up to 16 years was available. At the end of that time, five patients were dead of complications related to their disease; one patient remains alive 4 years after diagnosis but with severe respiratory compromise. ECD is a rare non-Langerhans' cell histiocytosis that may present as interstitial lung disease and resemble other pulmonary conditions, particularly usual interstitial pneumonitis and pulmonary Langerhans' cell histiocytosis. Recognition of this entity will allow better assessment of its true incidence, therapeutic options, and prognosis.

From the archives of the AFIP: pulmonary vasculature: hypertension and infarction.

Pulmonary hypertension is the hemodynamic consequence of vascular changes within the precapillary (arterial) or postcapillary (venous) pulmonary circulation. These changes may be idiopathic, as in primary pulmonary hypertension or pulmonary veno-occlusive disease, but more commonly they represent a secondary response to alterations in pulmonary blood flow. The pulmonary and systemic bronchial circulations form broad anastomoses that largely prevent infarction except in settings of markedly elevated pulmonary venous pressure, underlying malignancy, or excessive embolic burden. Causes of precapillary pulmonary hypertension include long-standing cardiac left-to-right shunt, chronic thromboembolic disease, and widespread pulmonary embolism arising from intravascular malignant cells, parasites, or foreign materials. The classic radiologic features of precapillary pulmonary hypertension are central arterial enlargement, sharply pruned peripheral vascularity, and right-sided heart hypertrophy and chamber dilatation. Postcapillary pulmonary hypertension may develop secondary to focal venous constriction or to compromised pulmonary venous drainage due to left atrial neoplasia, mitral stenosis, or left ventricular failure. Radiologic manifestations of postcapillary pulmonary hypertension include prominent septal lines, small pleural effusions, and occasionally air-space opacities. In addition, radiologic evaluation of postcapillary pulmonary hypertension may demonstrate evidence of pulmonary arterial hypertension, secondary to the retrograde transmission of elevated pulmonary venous pressure across the capillary bed.

Tumors of the thymus.

Thymic neoplasms are a common cause of an anterior mediastinal mass and may be benign or malignant. Thymic cysts are congenital or acquired and may be associated with a thymic malignancy. True thymic hyperplasia and thymic lymphoid hyperplasia may enlarge the thymus and simulate a neoplasm. Thymoma and thymic carcinoma are epithelial malignancies with distinct clinicopathologic features. Thymic carcinoid is a rare aggressive neuroendocrine malignancy associated with multiple endocrine neoplasia 1. Thymolipoma is a benign neoplasm. Hodgkin and non-Hodgkin lymphoma may primarily or secondarily involve the thymus. Primary mediastinal germ cell tumors may arise primarily within the thymus and include mature teratoma, seminoma, and non-seminomatous malignant germ cell tumors.

Thoracic carcinoids: radiologic-pathologic correlation.

Carcinoids are neuroendocrine neoplasms. Bronchial carcinoids are unusual, malignant primary neoplasms that characteristically involve the central airways and typically exhibit well-defined margins and bronchial-related growth. Bronchial carcinoids include low-grade typical carcinoids and the more aggressive atypical carcinoids. These tumors usually affect patients in the 3rd through 7th decades of life who are often symptomatic with cough, hemoptysis, or obstructive pneumonia. Bronchial carcinoids radiologically manifest as hilar or perihilar masses, with or without associated atelectasis, pneumonia, bronchiectasis, or mucoid impaction. At computed tomography, an anatomic relationship of these tumors to a bronchus is usually seen, and they may show contrast material enhancement or calcification. In rare cases, carcinoids occur in the thymus; when they do, they are aggressive tumors that affect adults who usually present with chest pain, cough, and dyspnea. Thymic carcinoids manifest radiologically as anterior mediastinal masses and may mimic thymomas. Thoracic carcinoids are treated by surgical excision. The prognosis for patients with typical bronchial carcinoids is excellent; patients with atypical bronchial or thymic carcinoids have a worse prognosis.

Opportunistic fungal pneumonia.

Opportunistic fungal infection is a common cause of serious morbidity and mortality in immunocompromised patients. These infections occur primarily in patients with chemotherapy-induced neutropenia, acquired immunodeficiency syndrome. or immunosuppression after solid organ or bone marrow transplantation. The most important opportunistic fungal pathogens include Cryptococcus neoformans, Candida and Aspergillus species, and the fungi that cause mucormycosis. Opportunistic pneumonia caused by previously unrecognized pathogens, such as Fusarium, Penicillium, and the dematiaceous fungi, are increasingly reported. The clinical and radiologic features of opportunistic fungal pneumonia are highly variable and often nonspecific. Diagnosis requires knowledge of the various modes of presentation, radiologic manifestations, and epidemiology of these infections. Because many of these organisms can colonize the upper airway, sputum cultures are considered diagnostically unreliable. Instead, definitive diagnosis requires culture of the fungus from infected tissue or demonstration of the organism on microscopic examination.

Pulmonary angiitis and granulomatosis: radiologic-pathologic correlation.

Five distinct clinical syndromes of pulmonary angiitis and granulomatosis are currently recognized: Wegener granulomatosis, lymphomatoid granulomatosis, necrotizing sarcoid granulomatosis, bronchocentric granulomatosis, and allergic angiitis and granulomatosis (Churg-Strauss syndrome). Patients typically present in middle age with fever, cough, hemoptysis, dyspnea, or chest discomfort. Upper airway involvement such as sinusitis suggests Wegener granulomatosis. Medical renal disease is associated with Wegener granulomatosis and Churg-Strauss syndrome. Asthma may be present in bronchocentric granulomatosis and Churg-Strauss syndrome. Pathologic examination of these entities demonstrates vasculitis, granulomatous inflammation, and parenchymal necrosis. The radiologic manifestations of pulmonary disease are varied, but the most typical appearance is that of multiple nodules or masses that may demonstrate cavitation. Diffuse multifocal air-space opacities with or without cavitation may also be seen. Pulmonary hemorrhage is a well-known presenting manifestation of Wegener granulomatosis and, less commonly, of Churg-Strauss syndrome. Because of the multifocal lung involvement in these diseases, pulmonary metastases and infectious causes are often considered in the differential diagnosis. Affected patients are treated with cytotoxic agents and corticosteroids. The prognosis is variable, depending on the specific syndrome, but may be favorable in the absence of significant complications.

Diffuse panbronchiolitis: histologic diagnosis in unsuspected cases involving North American residents of Asian descent.

OBJECTIVE: To study and report two cases of diffuse panbronchiolitis in patients of Asian ancestry residing in the United States and to review the literature pertaining to this disease. DESIGN: Diffuse panbronchiolitis is a progressive interstitial pneumonitis occurring primarily in Japan. Rare cases are now being identified in Europe and North America. Patients often have a history of sinusitis, present with dyspnea on exertion, and show a restrictive pattern on pulmonary function tests. The clinical, radiologic, and pathologic features of two cases of the disease received for consultation at the Armed Forces Institute of Pathology, Washington, DC, are reported with a review of the literature. RESULTS: Chest radiographs revealed bilateral small nodular opacities with ill-defined borders. High-resolution computed tomography demonstrated the abnormalities to have a centrilobular distribution. Histologically, there was transmural chronic inflammation centered on the terminal bronchioles and an interstitial infiltrate of foamy macrophages. CONCLUSION: Diffuse panbronchiolitis may be mistaken for other more common small airway diseases and may be underrecognized in Western nations. The immigration of Asians and sporadic case reports involving non-Asians make recognition of this disease entity important, as the implications for therapy are different than that of other small airway diseases.

Pulmonary inflammatory pseudotumor: radiologic features.

PURPOSE: To define the radiologic features of pulmonary inflammatory pseudotumor. MATERIALS AND METHODS: Between 1966 and 1994, 61 cases of pulmonary inflammatory pseudotumor involved 36 male and 25 female patients (age range, 17 months to 61 years; mean, 28 years). Clinical presentation, pathologic features, and radiologic findings were noted. RESULTS: At radiography, 52 patients had solitary peripheral nodules or masses, and extraparenchymal involvement--including hilar, mediastinal, and airway invasion--was found in 11. At computed tomography, 12 lesions were of heterogeneous attenuation and five, homogeneous. At T1-weighted magnetic resonance imaging, five lesions had intermediate signal intensity; of two lesions studied with T2-weighted imaging, two had high signal intensity; and the one lesion studied with gadolinium-enhanced imaging had diffuse enhancement. CONCLUSION: Pulmonary inflammatory pseudotumor was typically a solitary, peripheral, sharply circumscribed mass with an anatomic bias for the lower lobes. Local invasion and primary involvement of the mediastinum and hilar structures were unusual manifestations.

Primary mediastinal tumors: part II. Tumors of the middle and posterior mediastinum.

Lymphoma, mediastinal cysts, and neurogenic neoplasms are the most common primary middle and posterior mediastinal tumors. Lymphoma may involve the anterior, middle and/or posterior mediastinum, frequently as lymphadenopathy or as a discrete mass. Foregut cysts are common congenital mediastinal cysts and frequently arise in the middle mediastinum. Pericardial cysts are rare. Schwannoma and neurofibroma are benign peripheral nerve neoplasms, represent the most common mediastinal neurogenic tumors, and rarely degenerate into malignant tumors of nerve sheath origin. Sympathetic ganglia tumors include benign ganglioneuroma and malignant ganglioneuroblastoma and neuroblastoma. Lateral thoracic meningocele is a rare cause of a posterior mediastinal mass.

Mediastinal mature teratoma: imaging features.

OBJECTIVE: The purpose of this study was to characterize the cross-sectional imaging features of mediastinal mature teratomas. MATERIALS AND METHODS: Sixty-six cases of mediastinal mature teratoma were retrospectively reviewed, noting clinical, radiologic, surgical, and pathologic findings. The patient population consisted of 38 females and 28 males who were 1 week to 67 years old (mean age, 23 years 10 months). RESULTS: Forty-six patients presented with symptoms, predominantly chest pain, dyspnea, and cough. Twenty patients were asymptomatic. Fifty-four tumors were found in the anterior mediastinum, two in the posterior mediastinum, one in the middle mediastinum, and nine in multiple compartments. CT studies (n = 66) showed masses of heterogeneous attenuation with varying combinations of soft tissue, fluid, fat, and calcium. Soft-tissue attenuation was observed in 66 tumors (100%), fluid in 58 tumors (88%), fat in 50 tumors (76%), and calcification in 35 tumors (53%). The most frequent combination of attenuations was soft tissue, fluid, fat, and calcium, which was noted in 26 masses (39%). The combination of soft tissue, fluid, and fat was seen in 16 tumors (24%); and the combination of soft tissue and fluid was seen in 10 tumors (15%). Fat-fluid levels were seen in seven masses (11%). CONCLUSION: Mediastinal mature teratoma typically manifests on CT as a heterogeneous anterior mediastinal mass containing soft-tissue, fluid, fat, or calcium attenuation, or any combination of the four. Fluid-containing cystic areas, fat, and calcification occur frequently. Cystic lesions without fat or calcium were seen in 15% of tumors. Fat-fluid levels, considered highly specific for the diagnosis of mediastinal mature teratoma, are uncommon. CT is the imaging technique of choice in the evaluation of these lesions.

Primary mediastinal tumors. Part 1: tumors of the anterior mediastinum.

Primary anterior mediastinal neoplasms comprise a diverse group of tumors and account for 50% of all mediastinal masses. Thymomas are most common and can be locally invasive and associated with parathymic syndromes. Thymic carcinomas and thymic carcinoids are rare malignancies with a propensity for local invasion and distant metastases. Thymolipomas are benign thymic tumors. The mediastinal germ cell tumors are a heterogeneous group of benign and malignant neoplasms. Mediastinal lymphangiomas are rare tumors and predominantly occur in young children. In contrast, mediastinal goiters are relatively common in adults. Mediastinal parathyroid adenomas are an uncommon cause of persistent hyperparathyroidism and rarely cause a discernible mass. The clinical, radiologic, and therapeutic aspects of the most common masses are reviewed.

Intralobar sequestration: radiologic-pathologic correlation.

Intralobar sequestration accounts for 75% of pulmonary sequestrations. The lesion consists of lung tissue that lacks normal communication to the tracheobronchial tree, has systemic arterial supply, and shares the pleura of the parent lobe. The majority of intralobar sequestrations are probably acquired lesions. Patients usually present before the age of 20 years with recurrent infection. At pathologic examination, intralobar sequestration is characterized by inflammation and fibrosis. At radiologic examination, intralobar sequestration typically appears as a consolidation or mass, with or without cavitation, within a lower lobe. In many cases, cystic change may be present within the affected lobe. Identification of a systemic arterial supply supports the diagnosis. Patients are treated with surgical excision, and prognosis is favorable.