Immunohistochemical expression of podocyte markers in the variants of focal segmental glomerulosclerosis.

BACKGROUND Focal segmental glomerulosclerosis (FSGS) is the most prevalent primary glomerulopathy in Brazil and its incidence is increasing worldwide. Pathogenesis is related to podocyte injury, which may be due to several factors including viruses, drugs, immunology. In 2004, the Columbia classification of FSGS identified five histologic variants of the disease: collapsing (COL), usual (not otherwise specified, NOS), tip lesion (TIP), perihilar (PHI) and cellular variant (CEL). Several studies have demonstrated molecular changes in podocytes of FSGS patients. This study sought to classify a large series of FSGS biopsies according to the Columbia classification and analyze the occurrence of immunohistochemical differences among the five variants. METHODS Approximately 131 cases of renal biopsies with a diagnosis of primary FSGS during the period from 1996-2006 were classified according to the criteria of Columbia and were then submitted to immunohistochemical staining to the following antibodies: CD10, WT-1, Vimentin, Synaptopodin, α-actinin-4, GLEPP-1, cytokeratin (CK) 8-18, CK19 and Ki-67. RESULTS The FSGS classification resulted in 38.2% of NOS variant, in 36.6% COL, in 14.5% TIP, in 6.9% PHI and in 3.8% CEL. COL variant distinguished themselves among the others for having loss of expression of CD10, WT1 and α-actinin-4 (P < 0.05). Furthermore, COL gained expression of the CK8-18 and CK19 diverging from the other variants (P < 0.05). CONCLUSIONS COL variant of FSGS presented immunohistochemical characteristics that distinguished it from others pointing to additional studies in this area. The distinct immunohistochemical properties of COL might be of help in the comprehension of this aggressive form of FSGS.