PNETs

Last updated on Wednesday, September 10 2008 by jdmiles

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Atypical teratoid/rhabdoid tumor, BAF-47 immunohistochemical staining
Atypical teratoid/rhabdoid tumors are defined by mutations in the INI1 gene. BAF-47 recognized as the protein product of the INI1 gene, and therefore is diagnostic by its absence within tumor cells (note positive internal control reactivity with non-neoplastic blood vessels).

Atypical teratoid/rhabdoid tumor, intraoperative smear preparation x 400 (H&E stain).
Morphologic features of rhabdoid cells are best seen within cytologic preparations, where prominent nucleoli and abundant, inclusion-like eosinophilic cytoplasm can be appreciated.

Atypical teratoid/rhabdoid tumor, H&E stain x 400
Atypical teratoid/rhabdoid tumors are characterized by markedly enlarged atypical epithelioid cells with prominent nucleoli and abundant cytoplasm. On routine H&E staining, they resemble metastatic malignant amelanotic melanoma, but are generally encountered...

Atypical teratoid/rhabdoid tumor, sagittal section through cerebellum and brainstem, close-up
Atypical teratoid/rhabdoid tumors (ATRT) grow rapidly, with a tendency towards necrosis and hemorrhage. Most arise within the cerebellum.

Atypical Teratoid Rhabdoid Tumor, intraoperative smear preparation x 600 (H&E stain).
Morphologic features of rhabdoid cells are best seen within cytologic preparations, where prominent nucleoli and abundant, inclusion-like eosinophilic cytoplasm can be appreciated.

Atypical Teratoid Rhabdoid Tumor, ventral surface of brain.
A fungating mass can be seen extruding from the left cerebellar hemisphere. In this patient, tumor was present throughout the ventricular system of the brainstem, and extended out through the foramina into the subarachnoid space. In addition, the tumor extended...

Medulloblastoma, large cell anaplastic variant, H&E stain slide x 400
Approximately 10% of medulloblastomas will demonstrate anaplastic large cell features, characterized by enlarged nuclei with prominent nucleoli. Anaplastic Medulloblastomas are characterized by c-myc amplification and a more aggressive clinical course.

Medulloblastoma, classic type, H&E stained slide x 200.
Medulloblastomas classically demonstrate small, round, blue cells typical of embryonal tumors. Homer Wright rosettes are typically not seen in most areas of most medulloblastomas

Desmoplastic medulloblastoma, reticulin histochemistry x200
Desmoplastic medulloblastomas are characterized by reticulin-free islands ofbetter differentiated tumor separated by primitive neuroectodermal tumor cells within a dense reticulin network. This subtype of medulloblastoma typically presents in older children...

Desmoplastic medulloblastoma, Synaptophysin immunohistochemical staining x 100
Synaptophysin immunohistochemical staining highlights the reticulin-free pale islands of better differentiated tumor.

Desmoplastic medulloblastoma, H&E stain x100
Desmoplastic medulloblastomas are characterized by reticulin-free islands ofbetter differentiated tumor separated by primitive neuroectodermal tumor cells within a dense reticulin network. This subtype of medulloblastoma typically presents in older children...

Desmoplastic Medulloblastoma, H&E x200
Undifferentiated tumor in which are situated somewhat better differentiated synaptophysin positive pale islands.

Homer Wright rosettes, H&E stain x 200
Named for James Homer Wright (hence no hyphen), Homer Wright rosettes consist of a central core composed of neurofilaments surrounded by tumor cell nuclei. The absence of a true lumen classifies the structures, according to the Bailey classification, as a...

Medulloblastoma, leptomeningeal dissemination, ventral surface of spinal cord.
Medulloblastomas demonstrate a marked propensity towards leptomeningeal dissemination with entrapment and invasion of nerve roots and neural parenchyma.

Medulloblastoma, extensive leptomeningeal dissemination, ventral surface of brain
The leptomeninges are markedly thickened by tumor, resulting in cranial nerve damage, hydrocephalus, and re-invasion of tumor cells into brain parenchyma.

Medulloblastoma with extensive nodularity, H&E stain x 200
Medulloblastoma with extensive nodularity (MBEN) is a rare (less than 5%) subtype of medulloblastoma which occurs in very young patients (usually less than two years old) and is associated with indolent behavior even with relatively conservative therapy. ...

Medulloblastoma with extensive nodularity, H&E stain x 40
Medulloblastoma with extensive nodularity (MBEN) is a rare (less than 5%) subtype of medulloblastoma which occurs in very young patients (usually less than two years old) and is associated with indolent behavior even with relatively conservative therapy. Nodularity...

Medulloblastoma, mid sagittal section of brain
This medulloblastoma arose in the cerebellar vermis, grew across the fourth ventricle, and extensively invaded dorsal brainstem structures, as well as the thalamus and hypothalamus.

Medulloblastoma With Extensive Nodularity, H&E stain x 100
Medulloblastoma with extensive nodularity (MBEN) is a rare (less than 5%) subtype of medulloblastoma which occurs in very young patients (usually less than two years old) and is associated with indolent behavior even with relatively conservative therapy.

Medulloblastoma, reactive astrocyte, GFAP immunostain x 400
GFAP immunohistochemical staining is useful in differentiating trapped, reactive astrocytes from primitive astrocytic differentiation of the tumor cells.

Medulloblastoma containing reactive astrocytosis, GFAP immunohistochemical staining x 200
GFAP immunohistochemical staining is useful in differentiating trapped, reactive astrocytes from primitive astrocytic differentiation of the tumor cells.

Neuroblastoma with abundant neuropil and true rosettes, H&E stain x 100
Also called embryonal tumor with abundant neuropil and true rosettes

Homer Wright rosettes, synaptophysin immunohistochemical staining x 200
Strong synaptophysin immunoreactivity within Homer Wright rosettes indicates the presence of neuroblastic differentiation