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Chromosome 6 has been shown to contain at band q27 a minimal region of deletion associated with epithelial ovarian cancers and AF6, a gene disrupted in acute myeloid leukemia with t(6;11)(q27;q23). Using rapid amplification of cDNA ends by polymerase chain reaction, the breakpoint in AF6 was confirmed and a cDNA clone identified. This clone was used as a probe to screen a chromosome 6 cosmid library, and a single cosmid C-109F0645 was isolated. By fluorescence in situ hybridization, C-109F0465 was found to map distal to the critically deleted region associated with ovarian malignancies. AF6 is therefore distinct from and lies telomeric to this region.

Cytogenetic analysis of an endometrial polyp showed the presence of a t(6;20)(p21;q13) together with an ins(16;1)(q22;q32q42). Since a 6;20-translocation has been previously found in another endometrial polyp, we think that t(6;20)(p21;q13) may be a characteristic chromosomal change in endometrial polyps.

Two adenoid cystic carcinomas, one of the nasal cavity, the other a bronchial tumor, were cytogenetically analyzed. The former had a t(6;9)(q21-22;p 13-21) as the sole karyotypic abnormality. The latter had two related abnormal clones, resulting in the mosaic karyotype 46,XY,t(9;17)(p13;p13)/46,Y,t(X;6)(p22;q23),t(9;17)(p13;p13). The karyotypic profiles of the two cases, the only respiratory tract adenoid cystic carcinomas that have been cytogenetically characterized, differ little from those of previously reported adenoid cystic carcinomas of the major salivary glands, underscoring the fundamental biologic similarity among these tumors even when they develop from different structures and in different anatomical sites and organs. Because in the second case the t(9;17) obviously must have preceded the t(X;6), we conclude that both tumors had rearrangement of 9p13 as the primary cytogenetic change. The data thus add to the evidence that 6q changes are frequent, albeit at least sometimes secondary, aberrations in malignant salivary gland tumors. A subset of adenoid cystic carcinomas instead have rearrangement of 9p as the primary, and presumably pathogenetically essential, abnormality.

A new strategy for mapping chromosome translocation breakpoints in relation to known genes has been developed. This approach is based on the amplification by the polymerase chain reaction (PCR) of specific target sequences from small numbers of microdissected chromosome fragments. This method has been applied to leukaemia-associated translocations affecting the q23 region of chromosome 11. In two independent leukaemias, the t(6;11) translocation was distinguished from the t(9;11) and t(4;11) translocations by demonstrating that the former breakpoint on chromosome 11 lay proximal to the CD3D gene while the latter breakpoints lay distal to CD3D. All three translocation breakpoints were found to lie proximal to ETSI and THYI. The data suggest that although these leukaemia-associated breakpoints on chromosome 11 are cytogenetically identical they may involve disruption of different genes. This approach offers a rapid alternative to mapping by hybridisation of probes either in situ to chromosomes or to somatic cell hybrids containing the appropriate derivative chromosomes.

Uterine leiomyoma--a benign smooth muscle tumor--has recently been found to contain tumor-specific chromosome aberrations. Although only normal karyotypes were detected in 50 to 80% of cytogenetically investigated tumors, 104 leiomyomas with karyotypic aberrations have already been reported. At least four cytogenetically abnormal subgroups have been identified thus far, characterized by rearrangements of 6p, del(7)(q21.2q31.2), +12, and t(12;14)(q14-15;q23-24). The remaining abnormal tumors have had various nonrecurrent anomalies. Secondary karyotypic rearrangements, sometimes including ring chromosomes, have been found in one-third and reflect clonal evolution. Occasional leiomyomas have contained multiple numerical and structural rearrangements. Though benign, these cytogenetically grossly aberrant tumors often displayed more atypical histological features than are usually seen in leiomyoma. Multiple leiomyomas have been investigated from 69 patients, with detection of chromosome anomalies in at least two separate tumors from the same uterus in ten cases. In half of these patients unrelated aberrations were found in different leiomyomas from the same uterus. On other occasions the aberrations were identical, indicating that although some uterine leiomyomas originate independently, others may develop by intra-myometrial spreading from a common neoplastic clone. Some common features are discernible between the karyotypic pictures of uterine leiomyoma and angioleiomyoma; rearrangements of 6p, 13q, and 21q have been described in both tumor types. The cytogenetic similarities so far detected between leiomyoma and the malignant muscle tumors--leiomyosarcoma and rhabdomyosarcoma--are few and may be fortuitous. The cytogenetic profiles of leiomyoma and lipoma are strikingly similar; both tumor types have nonrandom rearrangements of 12q13-15, t(12;14) in leiomyoma and t(3;12) in lipoma, as well as variant rearrangements of the same 12q segment. Both also have cytogenetic subgroups characterized by changes in 6p and ring chromosomes. Finally, karyotypic similarities exists also between leiomyoma and pleomorphic adenoma of the salivary gland, which includes a subset of tumors with anomalies of 12q13-15, and with myxoid liposarcoma, which has t(12;16)(q13;p11) as a tumor-specific rearrangement.