Chondromyxoid fibroma of the nasal cavity with an interstitial insertion between chromosomes 6 and 19.

Chondromyxoid fibroma is an uncommon benign cartilaginous tumor that rarely presents in the sino-nasal region as a locally destructive, erosive lesion. Both clinically and histologically, it is a difficult diagnosis and can be confused with malignant processes such as myxoid chondrosarcoma. Histology of the tumor, especially with a small sample, can be challenging because of its heterogeneous nature showing an admixture of fibrous, myxoid, and chondroid areas. We are reporting unique cytogenetic findings in a case of chondromyxoid fibroma involving the floor of the nasal cavity with a clonal rearrangement between chromosomes 6 and 19. To our knowledge, karyotypes of 14 cases are reported in literature, with 11 cases reporting nonrandom, clonal abnormalities of chromosome 6. These results illustrate the distinctive nature of this tumor and may help identify genes involved in the pathogenesis of this tumor.

Y chromosome heterochromatin of differing lengths in two cell populations of the same individual.

OBJECTIVE: To present a prenatal diagnosis report on a case where G-banding analysis of fetal metaphase chromosomes showed populations of cells with two different Y chromosomes; one with a short block of heterochromatin (Yqh-) and one with a longer block of heterochromatin (Yqh+). METHODS: These two populations of the Y chromosome were studied using fluorescent quinacrine banding and fluorescent in situ hybridization (FISH). A chromosome paint corresponding to the euchromatic region of the Y chromosome, and probes corresponding to the SRY, DYZ1, and DYZ3 regions were used for this study. RESULTS: Both Y chromosomes appeared to be structurally normal by these analyses. Subsequent ultrasound examination at 20 weeks' gestation revealed normal male genitalia. Follow-up with a neonatal blood sample analysis confirmed the above findings. CONCLUSIONS: This study reports a direct prenatal diagnosis case of two populations of the Y chromosome in the same individual. This apparent mosaicism may be explained by a postzygotic simple deletion or unequal crossover event between sister chromatids in the DYZ region.