S-100 protein, fibronectin, and laminin immunostaining in lymphomas of follicular center cell origin.

Forty-nine paraffin-embedded biopsy specimens of involved nodal and extranodal tissue (bone marrow, spleen, and liver) from 13 patients with follicular center cell lymphomas (FCCL) and 14 with small lymphocytic lymphomas (SLL), including 11 cases with chronic lymphocytic leukemia, were tested for S-100 protein immunoreactivity. Analysis for fibronectin and laminin immunoreactivities was limited to the lymph node biopsy specimens. In FCCL, S-100-positive dendritic reticulum cells (DRCs) were found in 23 of the 26 tissue specimens examined, regardless of the involved sites and the growth pattern. Cases with completely or predominantly follicular pattern were usually associated with a spherical meshwork pattern of S-100-positive DRCs; in the FCCL specimens with a diffuse pattern (lymph nodes and bone marrow) as well as in the specimen areas with a minimally follicular tumor pattern, S-100-positive DRCs were consistently fewer in number and composed loosely aggregated nests. No S-100-positive DRCs were found in all the biopsy specimens in SLL. Concerning fibronectin and laminin immunostainings, results showed that no differences were present between areas of follicular and diffuse neoplastic growth and that the neoplastic growth of FCCL maintained for each antiserum the same distribution pattern as that seen in normal follicles. Analysis of the microenvironmental components as revealed with antisera used in the current study--particularly with anti-S-100 protein antiserum--appears to be a useful adjunct for the identification of FCCL in paraffin-embedded biopsy specimens, especially in extranodal sites.