CHROMOSOME REARRANGEMENTS IN SYNOVIAL CHONDROMATOUS LESIONS

Short-term cultures from one synovial chondroma and three cases of syn ovial chondromatosis, a lesion for which no previous karyotypic inform ation exists, were cytogenetically analysed. Whereas the chondroma dis played the relatively simple karyotype 46,XY,add(12)(q13),der(17)t(12; 17)(q13;q21), more complex changes were found in the three cases of ch ondromatosis: case 1, 47,XY,der(1)inv(1)(p13q25) del (1;12)(q25;q13),5,der(12)add(12)(p11)t(1;12)(p22; q13); case 2, 47,XY,add(10)(q26),+20 /46, idem, -6/46,XY,t(2;4)(q33;q21),add(21)(p11); and case 3, 44,XY,ad d(1)(p36),del(1)(p13p22),add(6)(p25). del(7)(q22q32),del(10)(q21),add( 11)(q13),-17,-18. The cytogenetic findings strongly suggest that synov ial chondro-matosis is a clonal proliferation. Apart from a near-diplo id chromosome number, the only recurrent cytogenetic features among th e four cases were loss of band 10q26 and rearrangements of 1p13 and 12 q13, found in two cases each. While chromosome bands 1p13 and 10q26 ha ve not been reported to be involved in other types of benign chondroma tous lesions, the 12q13-15 segment is recurrently rearranged in a vari ety of chondromatous rumours, e.g. pulmonary chondroid hamartomas. The present finding of translocations affecting band 12q13 in two of the cases emphasises that, irrespective of the anatomical localisation of the tumours, rearrangements of genes in 12q13-15 are important in the development of a large subset of benign and malignant cartilage-formin g tumours.