Recommended positive control: Tonsil, lymphoid tissues
Staining pattern: membrane
Reacitivity in normal cells: T lymphocytes. A small number of normal B-cells (John KC Chan. Tumors in lymphoretiucular system in Flercher et al. Diagnostic histopathology of tumors p1106)
1) Classification of B-cell lymphomas
small lymphocytic lymphoma/leukemia ~80%
mantle cell lymphoma ~95%
Follicular lymphoma and MALT lymphoma are negative.
Note: Alway compare to CD3, because normal T-cells are positive for thist marker.
Figure: Compare the number of positive cells of CD3 and CD5, the latter is much higher, indicating CD3-negative T-cells are showing positivity for CD5. Positive intensity in B-cells is usually lower than that of T-cells.
2) Some diffuse large B-cell lymphoma express CD5 (CD5-positive diffuse large B-cell lymphoma), showing poorer prognosis then negative cases.
3) Diagnosis of thymic carcinoma. Thymic cancer may show positive for CD5 (50%), and thymomas and carinomas oth other sites are negative.