hyaline vascular type-Castleman disease

Images

 hyalin vascular Castleman disease vs follicular lymphoma

• https://twitter.com/KyleBradleyMD/status/751426265165533184

Morphological synopsis

 Large follicles, scattered in mass of lymphoid tissue
 marked vascular proliferation
 hyalinization of abnormal germinal centers
 prominent germinal center showing well-developed vascular hyaline changes
 regressively transformed germinal centers
 many large cells with vesicular nuclei in hyaline center are follicular dendritic cells

• they may become atypical (dysplastic) in abnormal germinal centers and in intervening tissue
• cytogenetic and molecular evidence of clonality
• dysplasia of reticular/dendritic cells in Castleman disease. These cells are immunoreactive for desmin.
• formation of dendritic follicular tumors

 tight concentric layering of lymphocytes at periphery:

• corresponds to mantle zone
• results in onion-skin appearance

 Interfollicular stroma:

• prominent
• numerous postcapillary venule-type hyperplastic vessels
• admixture of: plasma cells, eosinophils, immunoblasts
• KP1-positive plasmacytoid monocytes

 Sinuses characteristically absent

 Vascular and related contractile (myoid) elements in interfollicular tissue:
when unduly prominent designated stroma-rich (stroma-rich variant).

• prominent stromal component
• richly vascularized
• further proliferation of this component results in formation of: angiomyoid proliferative lesions, angiomatous hamartomas or vascular neoplasms, sometimes hemangiopericytoma-like features
• vascular proliferation in the surrounding soft tissues

Morphological vaiants

 Variant lymphoid subtype:

• marked expansion of mantle zone
• small relatively inconspicuous germinal centers
• merges with process designated mantle zone hyperplasia

Immunochemistry

 Follicular dendritic cells in hyaline center

• strong immunoreactivity for CD21 and CD35
• Prominent network of CD21-positive dendritic follicular cells in the abnormal germinal center of Castleman’s disease.

 Polyclonal immunoglobulin production by plasma cells
 Large numbers of suppressor T cells in interfollicular areas
 An aberrant phenotype of Ki-B3-negative B lymphocytes in mantle zone cells
 FVIII-related antigen: strong positivity in endothelium of interfollicular vessels, weak and focal reaction in hyalinized vessels in center of follicles

Differential diagnosis

 angioimmunoblastic lymphadenopathy

 Large follicles have been confused with:

• Hassall corpuscles resulting in misdiagnosis of thymoma
• splenic white pulp resulting in misdiagnosis of ectopic spleen

 Variant lymphoid subtype: more likely to be confused with malignant lymphoma of follicular or mantle cell type.

See also

 Castleman disease

• plasma cell type of Castleman disease