MICROSCOPIC DESCRIPTION:
Paraffin sections show multiple small fragments of a densely hypercellular tumour. These are composed of atypical large cells with round and oval vesicular nuclei containing conspicuous amphophilic nucleoli and a narrow rim of pale cytoplasm. These cells show strong immunostaining for c-kit and patchy weak staining for placental alkaline phosphatase (PLAP) and CD30 and are admixed with moderate numbers of CD3+ T lymphocytes and lesser numbers of CD20+ B lymphocytes and CD68+ monocyte-macrophages. No staining for GFAP is
seen. The features are of germinoma. The topoisomerase proliferation index is approximately 40%. No normal pineal tissue is identified.
FINAL DIAGNOSIS: Germinoma