Type B1 Thymoma (Lymphocyte-rich) : Microscopic
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![Mediastinum_Thymoma_TypeB1__4B.jpg](/slides-13/slides/Mediastinum_Thymoma_TypeB1__4B.jpg)
Comments:
Type B1 thymomas resemble normal non-involuted thymus and show a predominance of cortical areas composed mostly of densely-packed non-neoplastic immature T-cells and scattered pale areas of medullary differentiation. One such medullary focus is shown here. The paler medullary areas are less cellular and contain few or no immature T-cells but have increased numbers of B cells and mature T-cells, and may have myoid cells and Hassall corpuscles.