Deep fibrous histiocytoma with a clonal karyotypic alteration: molecular cytogenetic characterization of a t(16;17)(p13.3;q21.3).

Deep fibrous histiocytoma, a rare lesion occuring in deep soft tissues, has recently been formally characterized as a diagnostically distinguishable variant of the benign fibrous histiocytoma spectrum with distinct morphological features. Nevertheless, because of the small number of cases published, information on their clinical behavior, including propensity for local recurrence and metastasis, is quite limited, and no molecular genetic or cytogenetic data are available. We report a 46,XY,t(16;17)(p13.3;q21.3) karyotype in a deep fibrous histiocytoma. Fluorescence in situ hybridization using bacterial artificial chromosome (BAC) clones refined the translocation breakpoints within 119.9 kb at 16p13.3 and 214 kb at 17q21.3. Moreover, to ascertain whether they may be nonrandomly involved in changes in this rare tumor type, we designed two dual-color break-apart probes with BAC clones, mapping proximally and distally to the two breakpoints, to be tested in additional archival cases by interphase fluorescence in situ hybridization. No break-apart signals were observed in the six additional cases studied, indicating either that the translocation is sporadic or that it is rare in deep fibrous histiocytoma. In conclusion, our data show that chromosome aberrations may be found in deep fibrous histiocytoma and that, as with cutaneous lesions, they may have clonal, at present nonrecurrent, chromosome changes.