Problems of detecting mosaicism in skin. A case of trisomy 8 mosaicism illustrating the advantages of in situ tissue culture

A case of mosaic trisomy 8 is described and the accuracy of flask culture and in situ culture techniques in detecting chromosomal mosaicism in tissues discussed. The advantages of the in situ method are illustrated and the importance of mixed colonies in defining mosaicism highlighted. The implications for prenatal diagnosis of mosaicism are pointed out.