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Pineal Tumors

 

 

Pathology

 

Germ Cell Tumors

Cellular Origin

Tumors arise from germ cells or less differentiated embryonal cells which migrate through the embryo. 

These cells localize in the gonadal ridges but may migrate to other midline sites, such as the brain.  This explains why cells of similar histologies to those in the pineal region may be found in the mediastinum and the retroperitoneum. 

 

Tumor Histology 

It is common for a tumor to have more than one different histological subtype, making it difficult to obtain accurate figures about the prevalence of certain tumor types.

Tumor type

Macroscopic Properties

Microscopic Properties

Germinoma

Poorly circumscribed

 

Cysts are uncommon

 

Gray/pink color

 

Large polygonal cells

 

Separated into lobules by blood vessels and connective trabeculae

 

Mitotic figures

 

Embryonal carcinoma

Large, hemorrhagic, necrotic tumors

 

Grow in solid sheets or form large tubular or papillary structures

 

Stroma:

  • loose and edematous OR
  • fibrous and hyalinized

 

Malignant-appearing epithelial cells

 

Coarse, irregular nuclear membrane

 

Mitotic figures

Choriocarcinoma

Granular, hemorrhagic, necrotic tumors

 

May be circumscribed, but often invades adjacent brain:

  • tentorium
  • falx
  • superior sagittal sinus

 

2 cell types:

1. cytotrophoblastic cells:

  • uniform
  • distinct borders
  • vesicular nucleus

2. syncytiotrophoblast cells

  • multinucleated
  • eosinophilic cytoplasm
  • vacuoles

Teratomas

Circumscribed

 

Round or lobulated

 

Solid and cystic areas

 

Benign

Components of all 3 germ layers:

 

  • Endoderm: GI and respiratory tissues, mucous-secreting glands
  • Mesoderm: bone, cartilage, muscle
  • Ectoderm: squamous epithelium, neural tissue

Pineoblastoma

Pink/ white/ gray colour

 

Cysts of gelatinous material

 

Hemorrhagic and necrotic (occasionally)

 

Malignant

 

Infiltrative

 

Scant, ill-defined cytoplasm

 

Similar appearance to medulloblastoma cells

 

Homer-Wright rosettes

 

Highly cellular

 

Poorly differentiated

Pineocytoma

Circumscribed

 

Less cellular than pineoblastoma

 

Hemorrhagic

 

Necrotic

Large cell nuclei

 

Often observe transition features between pineoblastoma and pineocytoma

 

Evidence for astrocytic and ganglion cell differentiation

 

Occasional Homer-Wright rosettes

 

Variable mitotic figures

 

May be poorly differentiated

 

 

 

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