Answer: Castleman’s disease

Histology: This enlarged lymph node exhibits multiple regressively transformed germinal centers surrounded by expanded mantle zones, which have a characteristic “onion skin” appearance. Some of the germinal centers are penetrated by markedly hyalinized blood vessels, acquiring a characteristic “lollipop” appearance.

Discussion: Castleman’s Disease (CD), also known as angiofollicular lymphoid hyperplasia, manifests as one of three histologic variants:
1) the hyaline vascular variant, which accounts for the majority of cases,
2) the plasma cell variant, and 3) the mixed hyaline vascular/plasma cell variant.

Like in our current example, the hyaline vascular variant of CD typically presents with a localized mass involving mediastinal or abdominal lymph nodes or lung. The regressed germinal centers consist predominantly of follicular dendritic cells, with occasional polyclonal B cells. The interfollicular areas are comprised of mostly T cells and polyclonal plasma cells. KSHV/HHV-8 has been demonstrated in a subset of plasma cell variant of Castleman’s disease. Multicentric Castleman’s disease is nearly always of the plasma cell variant, and may be associated with POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin symptoms).

The differential diagnosis includes progressive transformation of germinal centers, HIV-associated lymphadenopathy, and mantle cell lymphoma.

Reference(s):
– Amin HM, Medeiros LJ, Manning JT, Jones D. Dissolution of the lymphoid follicle is a feature of the HHV8+ variant of plasma cell Castleman’s disease. Am J Surg Pathol. 2003 Jan;27(1):91-100.