Castleman's disease

The value of magnetic resonance imaging (MRI) in the evaluation of vascular abnormalities in the chest is well established. To our knowledge, however, MRI in Castleman's disease of the chest had not been reported previously. We present a case of Castleman's disease of hyaline vascular type involving the pulmonary hilum where MRI was equal to computed tomography in showing the extent of the disease, but was more informative in demonstrating its relationship with vascular structures.

Castleman's disease or giant lymph node hyperplasia is a rare, benign disorder of unknown etiology involving lymph nodes at various sites, predominantly in the mediastinum.[1] Two histologic variants, hyaline vascular (HV) and plasma cell types have been described.[2] Since HV type is extremely hypervascular, it appears as a densely enhancing lesion on contrast-enhanced computed tomography (CT) and in parahilar regions may not be distinguishable from major vessels.[3]

Magnetic resonance imaging (MRI) has been used in evaluation of cardiovascular abnormalities.[4] We report a typical case of Castleman's disease in which MRI was helpful in defining the nature and extent of the disease.

CASE REPORT

A 45-year-old nonsmoking woman was referred from an outside hospital with the diagnosis of right parahilar mass that was discovered on routine chest radiographs and confirmed on non-contrast CT scan. She initially presented with 2 years' history of nonproductive cough and retrosternal chest pain. The pain has increased in intensity and was not associated with any other cardiac symptoms. A chest radiograph about a year ago had been reported as apparently abnormal and at that time, the patient refused further investigations. Findings from physical examination were unremarkable and results of laboratory investigations and electrocardiogram were normal.

Chest radiograph revealed a right hilar mass. Contrast-enhanced CT showed an enhancing lesion in the right parahilar area that was compressing the right main-stem bronchus and could not be separated from main pulmonary vessels (Fig 1). Transaxial MRIs showed this mass to be hypointense compared with mediastinal fat on [T.sub.1]-weighted images (TR/TE 633/20) and hyperintense on [T.sub.2]-weighted images (TR/TE 2000/100) (Fig 2, right). The mass extended between the right pulmonary artery and the right main-stem bronchus. The mediastinal lymph nodes also appeared hyperintense on [T.sub.2]-weighted images.

Abdominal and pelvic CT was normal. No endobronchial disease was noted on bronchoscopic examination and transbronchial biopsy specimens were not diagnostic. A percutaneous transthoracic fine-needle aspiration biopsy specimen showed large atypical cells; however, Hodgkin's disease could not be ruled out. Because lymphoma was considered a likely diagnosis, right thoracotomy was performed. A soft spongy mass measuring 3 x 4 cm in diameter was found located in between right main-stem bronchus and right pulmonary artery with enlarged hilar lymph nodes. Frozen section excluded malignancy and lymphoma.

Microscopically the lung mass and hilar lymph nodes showed features of Castleman's disease, HV type. The patient received no treatment and remained well after 1-year follow-up. Further CT of the chest revealed no change in right parahilar mass.

DISCUSSION

Castleman and colleagues[1] first described this entity in 1956 while reviewing the cases of tumors of the thymus. Subsequently, two distinct histologic types that differ in their clinical implications were recognized.[2] The more common HV type, which accounts for 80 to 90 percent of all cases, is usually asymptomatic or the patient may complain of cough or sensation of pressure due to tracheobronchial compression. In most cases (60 percent), the disease is seen in the thorax; however, it can occur in any other sites in which lymph nodes are normally found. In order of frequency, the intrathoracic sites involved include anterior mediastinum, the hila of lungs, and posterior mediastinum. Histologically, HV type contains small lymphoid follicles characterized by radially penetrating capillaries and concentric layering of surrounding lymphocytes. The interfollicular zones are well vascularized and contain varying numbers of small lymphocytes, scattered plasma cells, and occasional immunoblasts and suppressor T cells. Surgery may be curative. In less common plasma-cell type, extrathoracic sites are commonly involved and the patient may have fever, anemia, hypergammaglobulinemia, nephrotic syndrome, or peripheral neuropathy. Histologically, it has larger follicles with intervening sheets of plasma cells and is less vascular. Transition between two types has been described.

The radiographic findings of Castleman's disease are usually nonspecific. The lesions have been described as well rounded, lobulated soft-tissue masses.[5] The intrathoracic lesions have a tendency to lie on one side of midline or overlie the hilum. Unlike curvilinear calcification of cystic mediastinal lesions, the calcification in Castleman's disease is usually punctate and discrete.[6] As demonstrated in our patient, the dynamic CT scan shows densely enhancing soft-tissue lesion, especially in HV type.[3] The masses in Castleman's disease are very vascular and stain with a dense homogenous blush in the capillary phase of arteriography. Preoperative embolization of the feeding vessels, which may arise from bronchial arteries in the thorax or from lumbar arteries in the peritoneum, has been used to reduce the intraoperative hemorrhage.[7]

The ability to demonstrate vascular flow noninvasively makes MRI an excellent procedure for thoracic vascular evaluation. Moreover, because of flow void phenomenon, the vessels are clearly depicted, so soft-tissue abnormalities in the hilum can be detected easily.[8] Magnetic resonance imaging in this patient was not only of diagnostic value in demonstrating the exact size and extent of the tumor mass, but also its relationship with surrounding structures such as greater vessels fat planes and bronchi, which was later confirmed at surgery, while contrast-enhanced CT showed an enhancing lesion that could not be separated from pulmonary vessels. An interesting feature in this case was that corresponding mediastinal lymph nodes appeared hyperintense like the tumor mass on [T.sub.2]-weighted images. Thus, in Castleman's disease, although both MRI and CT scan can delineate the extent of the tumor mass equally, MRI appears to be more informative in demonstrating its relationship with vascular structures, which may be helpful when surgical resection of the mass is contemplated.

REFERENCES

[1] Castleman B, Iverson L, Menendez V. Localized mediastinal lymph node hyperplasia resembling thymoma. Cancer 1956; 9:822-30

[2] Keller A, Hochholzer L, Castleman B. Hyaline-vascular and plasma cell types of giant lymph node hyperplasia of the mediastinum and other locations. Cancer 1976; 29:670-83

[3] Onik G, Goodman P. CT of Castleman's disease. AJR 1983; 140:691-92

[4] Weinreb JC, Naidich DP. Thoracic magnetic resonance imaging. Clin Chest Med 1991; 12:33-54

[5] Olscamp G, Weisbrod G, Sanders D, Delrve N, Mustard R. Castleman's disease: unusual manifestations of an unusual disorder. Radiology 1980; 135:43-8

[6] Breatnach E, Myers J, McElvin R, Zorn G. Unusual case of calcified anterior mediastinal mass. Chest 1989; 1:113-15

[7] Walter J, Rottenburg R, Cannon W, Sheridan L, Pizzimente J, Orr J. Giant mediastinal lymph node hyperplasia: Castleman's disease angiographic and clinical features. AJR 1978; 130:447-50

[8] Gefter WB: Chest applications of magnetic resonance imaging: an update. Radiol Clin North Am 1988; 26:573-88

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