Follicular lymphoma (FL) with features reminiscent of hyaline-vascular Castleman disease (CD) is an unusual morphologic variant that may create diagnostic difficulties. To our knowledge, only 5 cases of this variant have been reported. We describe the clinicopathologic features of 6 cases including 2 men and 4 women with a median age of 63 years (range, 41-77). Morphologically, all lymph node biopsy specimens showed at least a focal area of conventional FL; 4 cases showed neoplastic follicles with hyalinized blood vessels penetrating into germinal centers (lollipop-like lesions); 4 cases had interfollicular areas with increased vascular stroma; 2 cases showed small neoplastic follicles with prominent, onionskin-like mantle zones; and 1 case showed 2 or more germinal centers within follicles (twinning). The small neoplastic follicles were more cellular than lymphocyte-depleted follicles of true hyaline-vascular CD, and the interface between germinal centers and mantle zones was ill defined. No cases showed dysplastic follicular dendritic cells. Immunohistochemistry for BCL-2 was positive in all 6 cases. Flow cytometry immunophenotypic analysis showed a monotypic B-cell population in 2 of 3 cases assessed. Conventional cytogenetic or fluorescence in situ hybridization studies performed in 3 cases showed t(14;18)(q32;q21) or IGH-BCL2, supporting the diagnosis of FL. The cases presented here add clinicopathologic data to the few cases of FL with hyaline-vascular CD-like features reported previously in the literature. Distinguishing this variant of FL from hyaline-vascular CD is important given the differences in treatment and prognosis of patients with each disease.
Keywords: BCL-2; Castleman disease hyaline-vascular variant; Castleman-like; Differential diagnosis; Follicular lymphoma; Mimicker.
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