A novel chromosomal translocation t(3;5)(q12;p15.3) and loss of heterozygosity on chromosome 22 in a multifocal follicular variant of papillary thyroid carcinoma presenting with skin metastases

Classic genetic rearrangements in papillary carcinoma of the thyroid involv e the RET- or TRK proto-oncogenes. We report a novel chromosomal translocat ion t(3;5)(q12;p15.3), confirmed by fluorescence in situ hybridization, in a multifocal follicular variant of a papillary carcinoma of the thyroid in a 79-year-old woman, with skin metastases as a presenting symptom. Three ye ars earlier, another cutaneous metastasis on her scalp was misdiagnosed as hidradenoma. Four tumour foci were recognized in the thyroid, two with a fo llicular variant of papillary carcinoma. To detect loss of heterozygosity, 14 chromosomes were investigated with 59 microsatellite markers. A clonal r elationship was detected between the two foci of tumour in the thyroid glan d containing follicular variant of papillary carcinoma and one of the skin lesions tested, all demonstrating loss of heterozygosity (LOH) in the same region of chromosome 22. Based on earlier reports, the low rate of LOH dete cted is in agreement with the diagnosis papillary carcinoma of the thyroid. Whole body scintigraphy performed after ablative therapy with radioiodine revealed multiple metastases in the lungs and skeleton. After repeated radi oiodine therapy, thyroglobulin under thyroxine suppression became undetecta ble and post-therapeutic scintigraphy revealed important regression of meta stases.