Spectral karyotyping demonstrates genetically unstable skin-homing T lymphocytes in cutaneous T-cell lymphoma

: We initially established cell lines from skin biopsies from four patients (MF8, MF18, MF19 and MF31) in early stages of cutaneous T‐cell lymphoma (CTCL) in 1999. After 3 weeks of culture, skin‐homing T lymphocytes were stimulated with phytohaemagglutinin. Metaphase spreads were analysed using spectral karyotyping (SKY), a molecular cytogenetic technique. MF18 and MF19 had predominantly normal karyotypes. MF8 had recurrent numerical aberrations resulting in two T lymphocyte clones: one with trisomy 21 (12/20 cells) and the other with monosomy chromosome 22 (3/20 cells). MF8 also exhibited a clonal deletion, del(5)(p15.1), as well as multiple non‐clonal structural aberrations. MF31 had a clonal deletion, del(17)(p12) and other non‐clonal deletions involving chromosomes 2, 5, 10, 11. MF18 had a single abnormal cell that contained two reciprocal translocations t(1;2)(q32;p21) and t(4;10)(p15.2;q24). In 2001, three of the original patients had new skin biopsies taken and cell lines were established. SKY analysis revealed the continued presence of a T‐cell clone in MF8 with trisomy 21 (4/20 cells). Additionally, a new clone was seen with a del(18)(p11.2) (17/20 cells). MF31 had only one aberrant cell with a del(17)(p12). MF18 had a clonal deletion, [del(1)(p36.1) in 3/20 cells] and non‐clonal aberrations involving chromosomes 3, 4, 5, 6, 12, 13, 17 and 18. Thus, three of four patients continued to show numerous numerical and structural aberrations, both clonal and non‐clonal, with only MF8 having a recurring T lymphocyte clone (+21). Our findings demonstrate high genetic instability among skin‐homing T lymphocytes even in early stages of CTCL. We did not see genetic instability or evidence of clones in cell lines from a patient with atopic dermatitis and one with psoriasis.