Cytogenetic studies in thyroid neoplasia were performed by G-banding of chromosome preparations obtained from the in vitro cultures of nine adenomas, one follicular carcinoma, five papillary carcinomas, and two medullary carcinomas. Complex structural chromosome aberrations were found in one adenoma. Two more adenomas, both composed of Hürthle cells, showed multiple numerical chromosome deviations with trisomy 4 and tetrasomy 7 in common. Six metastasizing carcinomas were characterized by normal stemlines, which indicates that malignancy in thyroid neoplasia cannot be excluded by cytogenetic techniques used currently. Comparisons between cytogenetic findings and cytophotometric DNA measurements in the material studied illustrate that euploid tumors represent a heterogenous group including cases with various gross structural chromosome aberrations of yet unknown clinical significance. Further studies of additional material with long-term follow-up are called for by our findings of structural and numerical chromosome aberrations in follicular neoplasms that are benign according to histologic criteria.

Cascade-free lifetime measurements of the y 3 F 2 3 4 0, the z 1 D 2 0 and the z 3 D 1 2 3 0 levels in La II have been made with the beam-laser technique. Our results, together with other recent lifetime measurements in La II, are compared with lifetimes inferred from transition probabilities measured by Corliss and Bozman (CB). An energy-dependent correction factor to the CB lifetimes is found, indicating a misjudgement of the effective temperature in Corliss' and Bozman's arc. A new value of the La solar photosphere abundance based on six transitions in La II, is presented.

The nuclear DNA content in thyroid cell imprints was determined in 94 patients with different thyroid diseases by single-cell cytophotometry. Sixty-three of the patients had benign thyroid lesions and 31 had different thyroid malignancies. The WHO tumor classification was used. The DNA values are presented in frequency histograms according to the ploidy and degree of proliferation. The histograms were classified into 6 groups: I, II, II+, III, IV, and IV +. The patients have been followed up for up to 6 years. With the exception of 1 case of thyrotoxicosis, the DNA values in benign thyroid lesions fell into group I-II or II +. Apart from 4 patients with small nodules of medullary carcinoma, the values in all patients with differentiated or anaplastic carcinomas were classified as group III, IV, or IV +.Determination of the DNA content may be a valuable adjunct in the differentiation between benign and malignant thyroid lesions. The presence of aneuploid cells seems to indicate a malignancy and in our material there was a clear difference in DNA content between follicular adenomas and follicular carcinomas.

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