What is Castleman Disease?
Castleman disease (CD) is a rare disorder characterized by the overgrowth of cells in the body's lymphatic system. It is also known as angiofollicular lymph node hyperplasia. This disease manifests in two forms: Unicentric Castleman Disease (UCD), which affects a single lymph node region, and Multicentric Castleman Disease (MCD), which involves multiple lymph node regions and can be associated with systemic symptoms.
Histological Features
Histologically, Castleman disease is distinguished by certain
microscopic characteristics. These features vary depending on whether the disease is unicentric or multicentric.
Unicentric Castleman Disease (UCD)
In UCD, the affected lymph node exhibits a mix of
hyaline vascular and
plasma cell patterns. The hyaline vascular type is more common and is characterized by small, hyalinized germinal centers surrounded by concentric rings of mantle zone lymphocytes, often referred to as an "onion-skin" pattern. The interfollicular regions may contain numerous blood vessels with hyalinized walls.
Multicentric Castleman Disease (MCD)
MCD shows a diffuse involvement of lymph nodes with
hyperplastic follicles and interfollicular plasmacytosis. The germinal centers are usually regressed, and the interfollicular regions are expanded and contain sheets of plasma cells. The lymph nodes might also demonstrate increased vascularity and the presence of
hyalinized vessels.
Pathophysiology
The pathophysiology of Castleman disease involves dysregulated
cytokine production, particularly interleukin-6 (IL-6). In MCD, elevated levels of IL-6 lead to systemic inflammatory symptoms and can contribute to the proliferation of lymphoid tissues. Human herpesvirus 8 (HHV-8) is also implicated in many cases of MCD, especially in patients who are immunocompromised.
Diagnosis
The diagnosis of Castleman disease often requires a combination of clinical, radiological, and
histopathological findings. A lymph node biopsy is essential to identify the characteristic histological features. Immunohistochemical staining may be used to detect the presence of HHV-8 in MCD cases.
Treatment
Treatment varies based on the type of Castleman disease. Surgical excision of the affected lymph node is often curative for UCD. In MCD, treatment is more complex and may include corticosteroids, anti-IL-6 therapy, immunomodulatory drugs, and antiviral agents if HHV-8 is present. The choice of treatment depends on the severity of the disease and the patient's overall health. Prognosis
The prognosis for Castleman disease varies. Patients with UCD generally have a good prognosis following surgical removal of the affected lymph node. However, MCD can be more challenging to manage due to its systemic nature and association with other conditions such as
HIV or
Kaposi's sarcoma. Early diagnosis and appropriate management are crucial for improving outcomes.
