The sections show scattered granulomas with adjacent lymphocytes and plasma cells. In addition, there is a proliferation of tumour cells. These form aggregates and singly. The tumour cells are large in size. They have enlarged clefted and hyperchromatic nuclei, focal prominent nucleoli and scanty cytoplasm.
The tumour cells are positive for: c-kit, placental alkaline phosphatase (PLAP) and CD10. Sparse cells are also CD15 positive.
They are negative for: AE1/3, CAM5.2, CD20, PAX-5, CD3, CD4, CD5, CD8, CD30, CD34, CD43, CD45, CD79a, CD138, bcl-2, bcl-6, MUM1, ALK-1, TdT, myeloperoxidase, lysozyme, c-Myc, EBER-CISH, CAM5.2, GFAP, S-100, SOX10, melan-A and synaptophysin.
The features are in keeping with germinoma. No other germ cell elements are seen. B-HCG and A-fetoprotein are negative. It is not possible to tell on histology alone whether this is primary or metastatic tumour and clinical correlation is required to make this distinction.
NB: Lymphoma has been excluded.