SSTR2a, a member of the
somatostatin receptor family, has been used as a diagnostic marker of
meningioma. However, the expression of
SSTR2a in follicular dendritic cells (FDCs) and their related
tumors has been poorly characterized. This study aimed to assess the potential diagnostic utility of measuring
SSTR2a immunohistochemically in FDCs and their related
tumors. We evaluated whole-tissue sections from 182 cases including 83 lymphoid reactive follicular
hyperplasias, 17
follicular lymphomas, 18 follicular dendritic cell
sarcomas (FDCSs), 6
inflammatory pseudotumor-like FDCSs, and 58 other histologic mimics. Immunohistochemistry for
SSTR2a and other FDC markers (CD21, CD23, CD35,
clusterin, and podoplanin) were performed in all 182 cases. Diffuse membrane immunoreactivity for
SSTR2a in FDCs was observed in 100% of
follicular lymphoma and FDCS cases and in 96.4% of the reactive follicular
hyperplasias cases. Notably, the positive rate of
SSTR2a in FDCSs was higher than that of CD21 (88.9%), CD23 (77.8%), CD35 (94.4%),
clusterin (55.6%), and podoplanin (94.4%). All
inflammatory pseudotumor-like FDCSs were negative for
SSTR2a. The histologic mimics were negative for
SSTR2a, except for 1
leiomyosarcoma case that showed focal (~10%) positive expression for
SSTR2a. Overall, our findings indicate that
SSTR2a is a highly sensitive and diagnostically useful marker for FDCs and FDCSs. Furthermore, immunohistochemistry for
SSTR2a may be helpful to distinguish FDCSs from
inflammatory pseudotumor-like FDCSs and other histologic mimics. Moreover, our findings suggest that
SSTR2a may be a potential therapeutic target for treatment of FDCSs.