Korean J Pathol.  2001 Aug;35(4):278-285.

Immunophenotype of Thymic Epithelial Tumors According to the New World Health Organization Classification

• Park SH
• Kim HS
• Kim HK
• Shin BK
• Hong SM
• Ro JY

Abstract

BACKGROUND
To identify the expression patterns and usefulness of various antibodies in making diagnoses and predicting prognoses, an immunohistochemical study was performed on thymic epithelial tumors (TETs).
METHODS
Forty-two cases of TETs were reclassified according to the new World Health Organization (WHO) classifications. CD3, CD5, CD79a, CD99, pan-, high- and low-molecular weight cytokeratins, EMA, vimentin, MIB-1 (Ki67) and p53 immunostaining were carried out.
RESULTS
There were two, twelve, eight, two, thirteen and one case for type A, AB, B1, B2, B3 and C, respectively. Combined B1/B2 and B2/B3 were 2 cases each. Fourteen cases (33.3%) had myasthenia gravis. CD99 was immunoreactive mainly in cortically derived lymphocytes, while CD3 and CD5 were immunoreactive in medullary-derived lymphocytes. CD5 immunoreactivity was negative in all thymic epithelial cells, except for one case of type B3. MIB-1 indices were highly expressed in cortical lymphocytes and some thymic epithelial cells, but did not show any correlation with grades. p53 in thymic epithelial cells was expressed in 6 (46%) out of 13 cases of type B3 and one case of type C, and it was negative in all other subtypes.
CONCLUSIONS
Only p53 was helpful for predicting high grades (B3 and C) (P<0.05). By MIB-1 indices, we could tell how many cortical immature lymphocytes were occupied in TETs, however, grading could not be achieved.

Keyword

Thymus gland; Neoplasms; Immunohistochemistry; World Health Organization; Histological classification

MeSH Terms

Antibodies
Classification
Diagnosis
Epithelial Cells
Immunohistochemistry
Keratins
Lymphocytes
Myasthenia Gravis
Prognosis
Thymus Gland
Vimentin
World Health Organization*
World Health*
Antibodies
Keratins
Vimentin