Argyrophilic nucleolar organizer regions in cells of thymoma and thymic carcinoma: correlation with DNA ploidy and clinicopathologic characteristics

Nucleolar organizer regions in oral squamous cell carcinoma

BACKGROUND AND AIMS

Several diagnostic methods are being employed to detect benign and malignant lesions, one of which is silver nitrate staining for organizer regions. The number of nucleolar organizing regions (NORs) can be used to show the degree of cell activity or metabolism in pathologic lesions. This study was designed to evaluate NORs as determi-nants of precancerous and squamous cell carcinoma.

MATERIALS AND METHODS

A silver colloid technique was applied on paraffin sections of 40 cases of oral squamous cell carcinoma and 25 cases of precancerous lesions; 15 specimens of normal epithelium were selected for the control group. After staining with silver nitrate, argyrophilic nucleolar organizer regions (AgNORs) were counted in 100 epithelial cells in three groups with the use of an oil immersion and ×1000 objective lens. One-way ANOVA and a post hoc Tukey test were used for statistical analysis.

RESULTS

The mean numbers and standard deviations of AgNORs were 1.58 ± 0.76 in normal epithelium, 2.1 ± 1.05 in pre-cancerous lesions and 2.43 ±1.33 in squamous cell carcinoma (SCC). There were statistically significant differences in Ag-NORs numbers between the groups (P<0.001) and significant differences in precancerous lesions between dysplastic and non-dysplastic epithelia (P<0.001). The mean AgNORs count per nucleus increased from healthy epithelium to precancer-ous lesion to SCC.

CONCLUSION

This study suggests that the silver staining technique for the detection of NORs (AgNOR) can be used to distinguish precancerous lesions and benign and malignant lesions.

Correlation between tumor angiogenesis and invasiveness in thymic epithelial tumors

OBJECTIVE

Because it is difficult to predict the behavior of thymomas on the basis of morphology alone, other methods for determining tumor aggressiveness must be explored. This study investigated the correlation between angiogenic grade and invasiveness in thymic epithelial tumors.

METHODS

Immunohistochemical studies of 46 surgically resected thymic epithelial tumors (18 noninvasive thymomas, 20 invasive thymomas, and 8 thymic carcinomas) were conducted. To highlight the microvessels, we used a specific monoclonal antibody against factor VIII. Expression of vascular endothelial growth factor and basic fibroblast growth factor was determined by using polyclonal antibodies.

RESULTS

Mean microvessel density readings for noninvasive thymomas, invasive thymomas, and thymic carcinomas were 4.6 +/- 3.2, 12.4 +/- 7.5, and 34.4 +/- 16.7, respectively. Stages I, II, III, and IV of thymoma had microvessel density readings of 4.6 +/- 3.2, 8.5 +/- 4.3, 13.8 +/- 7.7, and 22.0 +/- 6.8, respectively. These findings suggest a significant correlation between microvessel density and tumor invasiveness. Vascular endothelial growth factor expression in noninvasive thymomas, invasive thymomas, and thymic carcinomas was present in 1 (5.6%) of 18, 11 (55.0%) of 20, and 5 (62.5%) of 8 patients, respectively, thereby indicating a distinct association between vascular endothelial growth factor expression and increased microvessel density. Basic fibroblast growth factor expression was present in only 8 patients.

CONCLUSIONS

In patients with thymic epithelial tumors, there appears to be a significant correlation between tumor angiogenesis and invasiveness. Furthermore, our data suggests that this angiogenesis in thymic epithelial tumors might be, at least in part, dependent on vascular endothelial growth factor expression.