Pineal tumors Flashcards
Pineocytoma
Available grades: 1
Well-differentiated pineal neoplasm. Patients often present with Parinaud syndrome due to aqueductal obstruction.
Morphology: Moderately cellular neoplasm consisting of small, uniform, mature cells resembling pineocytes. Cells grow primarily in sheets and display frequent pineocytomatous rosettes of varying size, where cells surround a central collection of fibrillary processes.
IHC: Synaptophysin positive, with increased staining around pineocytomatous rosettes.
Molecular: No recurrent genetic aberrations are currently known.
Pineoblastoma
Available grades: 4
Morphology: Hypercellular, poorly differentiated, small, round blue cell tumor (embryonal morphology). Nuclear molding, brisk mitotic activity, and necrosis are often seen. Homer-Wright rosettes (eosinophilic material as false lumen) and less commonly Flexner-Wintersteiner rosettes (true lumen formation) may be seen.
Four subgroups: miRNA processing 1, miRNA processing 2, RB mutated, and MYC/FOXR2 activated.
Can be associated with the DICER1 syndrome (miRNA processing 1 and 2 groups).
Pineal parenchymal tumor of indeterminate differentiation
Available grades: 2-3
Morphologically in-between pineocytomas and pineoblastomas.
Associated with KBTBD4 mutations, which are not seen in true pineoblastomas.
Papillary tumor of the pineal region
Available grades: 2-3
Morphology: Epithelioid tumor with papillary features as well as more densely cellular areas. Often exhibits ependymal-like differentiation, with true rosettes and tubes. Occasionally, the tumor may be mostly solid with few recognizable papillae. Cells are pale to eosinophilic and columnar, occasionally with clear or vacuolated cytoplasm. Necrotic foci may be seen. Vessels are hyalinized and often have a pseudoangiomatous morphology, with multiple lumina.
Frequently display local recurrence after resection.
IHC: CD56+, E-cadherin negative
These markers are helpful in the differential of choroid plexus papilloma, which is E-cadherin positive and CD56 weak-to-negative.
Molecular: PTEN mutations.
Desmoplastic myxoid tumor of the pineal region, SMARCB1-mutant
Available grades: Not currently defined, but appears less aggressive than SMARCB1-deficient undifferentiated tumor.
Morphology: Composed of an admixture of variably dense cords of small to oval to spindled and epithelioid cells embedded in a heavily collagenized matrix. Tumour cells are dispersed within a loose pale basophilic myxoid matrix. Fascicular and whorling growth patterns may be seen, and irregularly shaped and elongated blood vessels with marked fibrosis are frequent. Scattered rhabdoid tumour cells are rare. Mitotic activity is low.
IHC: INI1/SMARCB1 lost, CD34+, EMA+.
Germinoma
Remember, germ cell tumors can also occur in the pineal region!
Germinoma is the equivalent of dysgerminoma in ovaries and seminoma in testes.
