Cytogenetic anomalies in hyaline vascular Castleman disease: report of two cases with reappraisal of histogenesis.

The pathogenesis of hyaline vascular Castleman disease (HVCD) is poorly understood. Although generally considered reactive in nature, a subset of cases has been shown to harbor focal proliferations of stromal cells, such as follicular dendritic cell (FDC) and angiomyoid proliferations. We report two typical cases of HVCD with cytogenetic anomalies: one was t(1;22)(qter;q13) and the other was t(7;8)(q37.3;q12) in cultured stromal cells, as demonstrated by conventional cytogenetic analysis. The cultured cells were immunoreactive for smooth muscle actin but negative for CD21, CD31, and CD34, and ultrastructurally possessed thin filaments (5-7.5 nm) with dense bodies, and pinocytotic vesicles, characteristic of smooth muscle cells. The lack of monoclonality of lymphoid cells in lesional tissues by immunohistochemical and molecular analyses also supports the origin of these anomalies from the stromal cells, most likely myoid cells. Moreover, the absence of overt stromal proliferations suggests that cytogenetic changes in stromal cells of HVCD precede histologic evidence of stromal overgrowth, which may account for the occurrence of angiomyoid proliferations arising in some cases of HVCD. Further studies with more cases are needed to decipher whether part or even most of HVCD cases bear genetic changes in the beginning of the disease without morphologically stromal overgrowth.