Argyrophilic nucleolar organizer regions in cells of thymoma and thymic carcinoma: correlation with DNA ploidy and clinicopathologic characteristics.
OBJECTIVE
To evaluate the usefulness of argyrophilic nucleolar organizer region (AgNOR) counting and flow cytometric DNA analysis in the differential diagnosis of thymoma and thymic carcinoma, as well as in the differences among various stages and histologic subtypes of these tumors.


METHODS
Paraffin-embedded blocks of 64 thymic epithelial tumors (20 noninvasive thymomas, 34 invasive thymomas, and 10 thymic carcinomas) were studied by AgNOR counting and flow cytometric DNA analysis. The thymomas were histologically classified as medullary, cortical, or mixed subtype.


RESULTS
Invasive thymomas had more AgNORs (-/+ SD) than noninvasive thymomas (7.93+/-2.90 vs 5.97+/-1.77; p < 0.01). The number of AgNORs of thymoma increased progressively with advances in stage (p < 0.01). Cortical thymomas had the highest number of AgNORs among the three subtypes (p < 0.05). Patients with thymoma who presented with myasthenia gravis also had a higher number of AgNORs (8.30+/-3.12 vs 6.50+/-2.03; p < 0.01). The AgNOR number did not correlate with the DNA ploidy of all specimens.


CONCLUSIONS
AgNOR counting is useful in differentiating between invasive and noninvasive thymomas, and in predicting the stage of thymomas. A greater number of AgNORs was observed in patients with cortical thymoma and in those who presented with myasthenia gravis.
Lee
Y C
YC
Chest Department, Veterans General Hospital-Taipei, School of Medicine, National Yang-Ming University, Taiwan. leeyc@vghtpe.gov.tw
Chern
J H
JH
Pan
C C
CC
Chang
S C
SC
Perng
R P
RP
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002277:Carcinoma / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D002467:Cell Nucleus / Q000648:ultrastructure; D004273:DNA, Neoplasm / Q000235:genetics*; D003937:Diagnosis, Differential; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009697:Nucleolus Organizer Region / Q000648:ultrastructure*; D011003:Ploidies; D016622:Silver Staining; D013945:Thymoma / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D013953:Thymus Neoplasms / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology
D004273:DNA, Neoplasm