Adult granulosa cell tumors of the ovary (GCTs) are sex cord stromal tumors of unpredictable behaviour. Up to now, the prediction of the relapsing/malignant potential remains difficult. CD56 (NCAM) in GCTs was previously described in only two studies. However, the expression of its isoforms was not examined.30 GCTs (16 primaries, 14 relapses) were investigated immunohistochemically with antibodies against Pan-CD56 (CD56Pan) and the isoform with 140/180 kDa length (CD56140/180 kDa). The reaction was assessed with respect to percentage of positive cells and intensity of staining.In all GCTs, CD56Pan was expressed, but differences were found between primaries and relapses. The percentage of CD56Pan positive tumor cells was lower in relapses, whereas CD56140/180 kDa showed a higher staining intensity in the latter.Expression of CD56 is an additional sensitive and helpful immunohistochemical tool for histopathologists diagnosing a GCT. It does not seem possible to provide a validly individual risk assessment. However, the different expression of CD56 isoforms might indicate important changes in the course to a more malignant behaviour.
