Children's Hospital San Diego
Diagnosis:
Malignant small blue cell tumor, favor medulloblastoma
Description:
Permanent sections confirm the intraoperative impression of a malignant small blue cell tumor characterized by sheets of monomorphic polygonal cells with vesicular chromatin and small amounts of surrounding amphophilic cytoplasm. Mitotic activity is readily identified. The tumor appears to spread up under the meninges, where there is a small amount of hemosiderin deposition as well as mineralization of leptomeningeal walls. There are no rhabdoid cells or prominent nucleoli. There is a vague focal hint of neural rosette formation. The tumor focally shows extensive necrosis, with surrounding fibrous reaction and hemosiderin deposition.
Immunohistochemistry:
| S100: | Small number of diffusely scattered tumor cells strongly positive. |
| NSE: | Tumor cells negative. |
| GFAP: | Tumor cells generally negative, although a few positively staining cells are noted at disrupted areas of the specimen or edges of the specimen where larger cells consistent with reactive astrocytes are noted. | Ewings 013/CD99: | Tumor cells negative. |
These findings support the impression of a primitive malignant tumor with some neural differentiation, consistent with a diagnosis of supratentorial primitive neuroectodermal tumor.
Johns Hopkins - Dr. Peter Burger
Interpretation and Diagnosis:
Malignant Neoplasm, see comment
Comment:
The mitotically active lesion is difficult to classify. The presence of necrosis with pseudopalisading is more consistent with malignant glioma but the tumor is histologically more monomorphic than most malignant astrocytomas, and a front of invasion is not identified. There are small perivascular clearings but the tumor is not to us ependymoma. The sheet-like compactness is consistent with medulloblastoma but the tumor is looser than most medulloblastomas and contains diffuse mucopolysaccharide.
St. Jude
Diagnosis:
High grade malignant neoplasm, suggestive of primitive neuroectodermal tumor (see description)
Description:
Sections from the "brain tumor" show a hypercellular lesion composed of generally patternless sheets with rounded to oval nuclei with minimal surrounding cytoplasm, set within a background of delicate fibrillary to focally myxoid material. The mitotic rate is brisk and there are multiple foci of necrosis present. Multiple immunohistochemical stains were performed at our institution. The tumor cells are negative for synaptophysin and chromagranin, while a Ki-67 (MIB-1) divulges a markedly elevated proliferation rate. Scattered individual tumor cells are positive for neurofilament protein, while glial fibrillary acidic protein (GFAP) decorates only rare cells within the lesion, likely representing reactive astrocytes. p53 stains many of the tumor cell nuclei.
This hypercellular tumor represents a high grade malignant neoplasm. This case is difficult to classify as it does not have a classic histologic appearance of a typical embryonal tumor. It has a somewhat glial appearance in areas by microscopy, though does not mark with GFAP, and the findings of definite positivity of at least a subpopulation of tumor cells for neurofilament suggests that this may represent a primitive neuroectodermal tumor.