Abstract
The relationship between epithelial cell type, clinical behaviour and number of nucleolar organiser regions (AgNORs) was investigated in 37 thymomas and three thymic carcinomas. The thymomas were classified according to epithelial cell morphology as cortical (16 cases), medullary (8 cases) or mixed (13 cases). Seven cortical tumours had infiltrated the capsule or adjacent structures at the time of operation, whereas only one medullary and two mixed tumours showed evidence of invasion, the differences being statistically significant (P < 0.01). None of the patients with medullary thymoma had myasthenia gravis, but there was a significantly higher incidence (P < 0.001) among those with cortical or mixed tumours (six and three cases respectively). The mean AgNOR count for medullary tumours was 1.56, compared with 2.22 and 2.06 for cortical and mixed tumours. Although the counts for medullary tumours were significantly lower than for the other two types (P < 0.01), there was considerable overlap. The mean count for the carcinomas was 4.94 - significantly higher than for the thymomas (P < 0.01) - but again overlap was considerable. No relationship was demonstrable between AgNOR counts, clinical stage, incidence of myasthenia or recurrence. It is concluded that although classification of thymomas based on epithelial cell type represents an improvement on previous classifications, it must be applied with caution. Similarly, AgNOR counts may give some indication of malignant potential, but their usefulness in individual cases is doubtful.
Original language | English |
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Pages (from-to) | 203-213 |
Number of pages | 11 |
Journal | Analytical Cellular Pathology |
Volume | 3 |
Issue number | 4 |
Publication status | Published - Jul 1991 |
Externally published | Yes |
Keywords
- AgNOR counts
- Classification
- Epithelial cell type
- Thymoma