Castleman disease (angiofollicular lymph node hyperplasia) is a rare non-neoplastic or lymphoproliferative disorder of lymphoid tissue. Two main types: unicentric (localized — 70%) and multicentric (30%). Hyaline vascular variant is most common (90%) in unicentric type, presenting as a localized, markedly homogeneously enhancing solid mass in the mediastinum — enhancement degree equal to or greater than spleen. Multicentric type is associated with HHV-8 and HIV showing systemic symptoms (fever, night sweats, weight loss), widespread lymphadenopathy, splenomegaly, and hepatomegaly. Most commonly in anterior or middle mediastinum, less commonly posterior. Usually occurs in young adults aged 20-40. Surgical resection is curative for unicentric type (>90% cure rate). Multicentric type requires systemic therapy (rituximab, siltuximab — anti-IL-6) and regular follow-up due to lymphoma transformation risk.
Age Range
20-50
Peak Age
35
Gender
Equal
Prevalence
Rare
Castleman disease is lymphoid tissue hyperplasia triggered by interleukin-6 (IL-6) overproduction. Unicentric hyaline vascular type shows hyalinized vessels in germinal centers, concentric lymphocyte arrangement ('onion skin' pattern), and rich interfollicular vascularity — this intense vascularity forms the basis of marked enhancement on imaging. Interfollicular capillary proliferation causes dense contrast accumulation producing spleen-like enhancement. In multicentric type (usually plasma cell variant), HHV-8 infection produces viral IL-6 (vIL-6) causing systemic inflammatory response and polyclonal lymphoid proliferation. IL-6 overproduction leads to anemia, hypergammaglobulinemia, fever, and elevated acute phase reactants. Calcification (in 10-15% of cases) reflects calcium deposition in degeneration of hyalinized vessels — stellate peripheral calcification is characteristic.
A solid mass in the mediastinum with marked homogeneous enhancement equal to or greater than spleen is highly specific for Castleman disease (hyaline vascular type). This degree of enhancement is not expected in other mediastinal masses.
Markedly homogeneously enhancing solid mass in arterial phase — enhancement degree equal to or greater than spleen. Close relationship with great vessels. Size usually 5-10 cm. Necrosis is rare (unlike thymic carcinoma). Enhancement is homogeneous and smooth — heterogeneous enhancement or necrosis should prompt alternative diagnoses. Well-circumscribed, capsule may be visible. Washout pattern: intense enhancement in arterial and venous phase with mild decrease in delayed phase (hypervascular pattern).
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A well-circumscribed, markedly homogeneously enhancing solid mass in the mediastinum with enhancement equal to or greater than spleen, suggesting Castleman disease (hyaline vascular type) as the leading diagnosis.
Feeding artery (usually bronchial artery or intercostal artery branch) and draining vein of the mass may be prominent. Reflects arterial blood supply of hypervascular mass. Feeding artery is dilated — vessel caliber increased to meet increased blood flow. This finding is important for preoperative embolization planning — embolization before surgery can reduce bleeding risk.
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The mass has prominent feeding artery and draining vein, consistent with hypervascular mass; preoperative embolization may be considered.
Calcification seen in 10-15% of cases. May be stellate peripheral or central calcification — stellate pattern is highly characteristic of Castleman disease. Coarse or punctate calcifications may also be seen. Calcification supports Castleman diagnosis and helps differentiate from thymoma (calcification rare in thymoma).
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Stellate calcification within the mass is observed, consistent with Castleman disease (hyaline vascular type).
Intermediate to high signal on T2. Homogeneous signal pattern typical. Flow void structures (signal loss from fast-flowing blood) may be seen — reflecting rich vascularity. Marked homogeneous enhancement on contrast T1 parallels CT findings. MRI is superior to CT especially for posterior mediastinal location and spinal canal relationship evaluation.
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The mass shows intermediate-high T2 signal, flow void structures, and marked homogeneous enhancement on contrast T1; consistent with Castleman disease.
Variable diffusion pattern on DWI. Hyaline vascular type generally shows no significant diffusion restriction — wide vascular spaces and loose lymphoid tissue allow free water diffusion. ADC values are intermediate-high. Plasma cell variant's higher cellular density may restrict diffusion. DWI may help differentiate Castleman from lymphoma — lymphoma usually shows more prominent diffusion restriction.
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No significant diffusion restriction on DWI, consistent with hyaline vascular type Castleman disease.
FDG uptake varies in unicentric hyaline vascular type (SUVmax 2-8) — rich vascularity contributes but neoplastic proliferation is low. Multicentric type shows widespread lymphadenopathy with high FDG uptake — IL-6-mediated inflammatory activity causes high uptake. PET-CT used for extent assessment in multicentric disease and lymphoma exclusion. Also important for treatment response monitoring.
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The mass shows moderate FDG uptake on PET-CT (SUVmax: __); consistent with Castleman disease.
Criteria
Most common type (70% unicentric, 90% of which hyaline vascular). Localized mass. Usually asymptomatic.
Distinct Features
Marked homogeneous enhancement (equal/greater than spleen), well-defined, necrosis rare, surgery curative (>90% cure rate), excellent prognosis. Feeding artery and draining vein may be prominent. Calcification 10-15%.
Criteria
Less common (10% of unicentric). May have systemic symptoms (fever, anemia, hypergammaglobulinemia).
Distinct Features
Less prominent enhancement (less than hyaline vascular type), may be larger, systemic symptoms may accompany. IL-6 elevation more prominent. Symptoms resolve after surgery.
Criteria
Widespread lymphadenopathy + systemic symptoms (fever, night sweats, weight loss). HHV-8/HIV-associated. Increased lymphoma risk.
Distinct Features
Widespread LAP, splenomegaly, hepatomegaly, B symptoms. Multiple enhancing lymph nodes on CT/PET-CT. Poor prognosis — lymphoma transformation risk (especially HHV-8 associated). Systemic therapy required; surgery not curative.
Distinguishing Feature
Thymoma shows moderate enhancement (less than spleen). Castleman shows marked enhancement (equal/greater than spleen). Enhancement degree is the most important differentiating criterion. Thymoma may have paraneoplastic syndromes. Thymoma usually 40-60 years, Castleman 20-40.
Distinguishing Feature
Lymphoma shows moderately enhancing widespread lymphadenopathy. Castleman (unicentric) is markedly enhancing SINGLE mass — no widespread LAP. B symptoms suggest lymphoma. Biopsy is definitive. Both may show FDG uptake on PET-CT.
Distinguishing Feature
Thymic carcinoma is heterogeneous, necrotic, irregular, invasive mass. Castleman is homogeneously enhancing, necrosis rare, well-defined. Thymic carcinoma shows aggressive behavior (invasion, metastasis); unicentric Castleman remains localized.
Distinguishing Feature
Reactive lymphadenopathy usually shows multiple, small (<2 cm), moderately enhancing nodes. Castleman (unicentric) is single large mass (5-10 cm) with marked enhancement. Enhancement degree and size are important differentiators. Multicentric Castleman may be confused with reactive LAP — biopsy needed.
Urgency
routineManagement
surgicalBiopsy
NeededFollow-up
6-monthSurgical resection is curative for unicentric Castleman disease (>90% cure rate). Preoperative embolization may reduce bleeding risk in hypervascular mass. Diagnosis usually confirmed by biopsy — even typical imaging findings require histological confirmation because lymphoma must be definitively excluded. Multicentric type requires systemic therapy (rituximab — anti-CD20, siltuximab — anti-IL-6). HIV/HHV-8 associated multicentric: antiretroviral therapy + rituximab. Regular follow-up (6-month CT/PET-CT) mandatory for multicentric type due to lymphoma transformation risk — especially DLBCL development.
Hyaline-vascular type Castleman disease is cured by surgical resection. Multicentric type has a more aggressive course and requires systemic treatment. Biopsy should be performed carefully due to hypervascularity. HHV-8 associated multicentric type is seen in HIV-positive patients.