Catarina Petersson

Cytogenetic findings in phyllodes tumors of the breast: Karyotypic complexity differentiates between malignant and benign tumors☆

Clonal karyotypic abnormalities were detected in short-term cell cultures from six phyllodes tumors of the breast. Whereas all five benign tumors had simple chromosomal changes, the highly malignant one had a near-triploid stemline, indicating that karyotypic complexity is a marker of malignancy in phyllodes tumors. Interstitial deletions of the short arm of chromosome 3, del(3)(p12p14) and del(3)(p21p23),were the only aberrations in two benign tumors. Cytogenetic polyclonality was detected in three benign tumors: two had cytogenetically unrelated clones, whereas the third had three different, karyotypically related cell populations as evidence of clonal evolution. The finding of clonal chromosome abnormalities in both the epithelial and connective tissue components of the phyllodes tumors indicates that they are genuinely biphasic, that is, that both components are part of the neoplastic parenchyma.

Karyotypic abnormalities in fibroadenomas of the breast

Short‐term cultures of 50 fibroadenomas of the breast were cytogenetically analyzed. Nine tumors were found to display clonal chromosome aberrations. One had multiple, cytogenetically unrelated clones, whereas the others had a single abnormal clone each. Four cases had one balanced translocation as the sole anomaly, and one had a complex intrachromosomal rearrangement of chromosome 3, leading to loss of 3p material. One fibroadenoma had a single numerical aberration, and one had supernumerary ring chromosomes. The remaining 2 cases had both numerical and structural aberrations. The only recurrent alterations were trisomy 20 and rearrangement of chromosome arm 1p. The finding of similar chromosomal aberrations in fibroadenomas and carcinomas suggests that women with karyotypically abnormal fibroadenomas may have an increased risk of developing subsequent breast cancer. If so, different chromosome anomalies might have different pathogenetic and/or prognostic significance. Int. J. Cancer, 70:282–286, 1997.

Chromosome aberrations in prophylactic mastectomies from women belonging to breast cancer families

Short‐term cultures of samples from eight prophylactic mastectomies from five unrelated women who where genetically predisposed to breast cancer were analyzed cytogenetically. Clonal chromosome abnormalities were detected in five breasts. Three samples from two women had aberrations involving the short arm of chromosome 3, with a breakpoint in 3p14 in common. Three samples from three women had rearrangements of 1 q. Two of them, one of which also displayed a 3p14 rearrangement, shared a breakpoint in 1q41. Both 1q41 and, in particular, 3p14 have been reported to be rearranged frequently in malignant breast proliferations. Whether alterations of genes in these bands are essential in mammary tumorigenesis and, if so, whether they are equally important in sporadic and in hereditary cases remains to be explored. Genes Chromosom Cancer 16:185–188 (1996).

Karyotypic changes in phyllodes tumors of the breast

Cytogenetic analysis of short-term cultures of five phyllodes tumors of the breast-classified as benign (one tumor), borderline malignant (two tumors removed from the same breast in 1991 and 1993), and malignant (two tumors)--revealed clonal changes with simple structural abnormalities in the benign tumor, the borderline malignant tumors, and one malignant tumor in which benign areas and areas of borderline malignancy were also present. In contrast, the malignant tumor without admixed borderline malignant or benign areas had a complex karyotype. The karyotype of the benign phyllodes tumor was 46,XX,del(12)(p11p12)/46,XX,t(8;18)(p11;p11)/46,XX. The first borderline malignant phyllodes tumor had t(3;20)(p21;q13) as the sole abnormality. When the tumor recurred, this was no longer the only clone detected and the tumor karyotype was now 46,XX,t(3;20)(p21;q13)/46,XX,t(9;10)(p22;q22)/46,XX,t(1;8) (p34;q24)/46,XX,del(11)(q22-23)/46,XX. The malignant/borderline malignant/benign tumor had t(1;6)(p34;p22) as the sole clonal abnormality. Finally, the karyotype of the malignant phyllodes tumor which contained no benign or borderline malignant areas was 42,XX,der(1)t(1;4)(q21;q21),der(3)t(3;17)(q29;q21), -4,i(8)(q10), -10, -13,i(13)(q10),der(14)t(1;14)(q21;p11),der(14)t(4;14) (p12;p11), -17/80-90,idemx2, +del(1)(q12), +i(1)(p10), +dic(5;5)(p14;p14), +i(6)(p10), +del(7)(p11), +dup(7)(q11q36), +i(15)(q10),inc/46,XX. The findings indicate some cytogenetic similarities between benign/borderline malignant phyllodes tumors and fibroadenomas of the breast, presumably reflecting similar pathogenetic mechanisms in the two types of mixed-lineage tumors.

Different cytogenetic patterns in skeletal breast cancer metastases

Short‐term cultures of breast cancer metastases to bone from two patients were analyzed cytogenetically. One metastasis had a complex hypotriploid karyotype with numerous marker chromosomes, whereas the other had simple karyotypic changes in three unrelated clones, 46,XX, t(4;11)(p14;p13)/45,XX,‐19/46,XX,del(3)(p13p23), suggesting that the metastasis had originated from a simultaneous invasion of multiple cells from the primary tumor. The metastasis with complex chromosomal aberrations developed quickly as part of a clinically aggressive disease, whereas that with simple changes developed more than 20 years after the initial breast cancer diagnosis. Our findings therefore indicate that the tumor karyotype may play a role in determining the clinical course in patients with breast cancer. Genes Chromosom Cancer 16:72–74 (1996).