A retroperitoneal neurofibrosarcoma infiltrating the spine of a a-year
-old boy was investigated cytogenetically three times over a 5-month p
eriod. The first sample, from a diagnostic fine-needle aspiration biop
sy, had a supernumerary i(1)(q10) as the sole clonal aberration; two c
ells showed monosomy 18 in addition to the isochromosome. The second s
ample, obtained at tumor resection 3 weeks later, had the karyotype 47
,XY, +i(1)(q10), -18, +21/45,XY, -18. After 5 months, a large local re
currence was resected. The chromosome analysis showed further clonal e
volution: 45,XY, +1,der(1;11)dic(1;11)(q44;q13)i(1)(q10), inv(6)(p21q1
2), -17. The findings indicate that formation of i(1)(q10) and loss of
chromosome 18 may be early genetic events in neurofibrosarcoma develo
pment.