DNA fragmentation and DNA repair synthesis induced in rat and human thyroid cells by chemicals carcinogenic to the rat thyroid.

Five chemicals that are known to induce in rats thyroid follicular-cell adenomas and carcinomas were assayed for their ability to induce DNA damage and DNA repair synthesis in primary cultures of human thyroid cells. Significant dose-dependent increases in the frequency of DNA single-strand breaks and alkali-labile sites, as measured by the same Comet assay, were obtained after a 20-h exposure to the following subtoxic concentrations of the five test compounds: methimazole from 2.5 to 10mM; nitrobenzene, potassium bromate, N,N'-diethylthiourea and ethylenethiourea from 1.25 to 5mM. Under the same experimental conditions, DNA repair synthesis, as evaluated by quantitative autoradiography, was present in potassium bromate-exposed thyroid cells from all the three donors and in those from two of three donors with either nitrobenzene or ethylenethiourea, but did not match the criteria for a positive response in thyroid cells from any of the donors with methimazole and N,N'-diethylthiourea. Consistently with their ability to induce thyroid tumors, all the five test compounds, administered p.o. in rats in a single dose corresponding to 1/2 LD50, induced a statistically significant degree of DNA fragmentation in the thyroid. These findings suggest that the five test compounds might be carcinogenic to thyroid in humans.

Gastrointestinal stromal tumors: clinical pathological review of a personal series.

The Authors report their experience on the management of gastrointestinal stromal tumors (GISTs). In addition to recent cases immediately diagnosed as GISTs, a pathological review of stored material from non-epithelial tumors of the gastrointestinal tract operated on over the past 20 years was performed. Twenty-three out of a total of 31 cases were shown to be positive for the immunophenotypic characteristics (CD117/CD34) of GISTs. Most cases (approximately 60%) were symptomatic, with hemorrhage being the most common presenting sign, followed by occlusion, pain and perforation. Asymptomatic cases were detected incidentally during procedures for other conditions. Diagnostic techniques (ultrasound, endoscopy, endoscopic ultrasound, X-ray, CT, MRI) allowed only the detection of wall (extraluminal) involvement. Apart from differentiating between benign and malignant, preoperative biopsy was seldom valuable. All cases were treated surgically, with intervention tailored to location and anatomical/surgical and anatomical/pathological features. Long-term follow-up was conducted in all patients and for most is still ongoing: five patients died from recurrent disease at varying intervals after surgery (from 17 to 102 months). Relationships between observed aggressiveness and risk were studied. Parameters that may prove useful for the early detection and appropriate management of these lesions are discussed.