CNS & pituitary tumors

Pineal tumors

Desmoplastic myxoid tumor of the pineal region, SMARCB1 mutant



Last author update: 8 July 2022
Last staff update: 8 July 2022

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PubMed Search: Desmoplastic myxoid tumor, SMARCB1 mutant

Mariana Voudouri, M.D.
George Zanazzi, M.D., Ph.D.
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Cite this page: Voudouri M, Zanazzi G. Desmoplastic myxoid tumor of the pineal region, SMARCB1 mutant. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/cnstumorSMARCB1mutant.html. Accessed February 3rd, 2023.
Definition / general
  • Pineal region neoplasm with ovoid or spindle shaped cells, containing inactivating alterations of the SMARCB1 / INI1 locus and variable amounts of desmoplasia and myxoid matrix
Essential features
  • Predominates in adults and adolescents
  • Arises in the pineal region
  • Small to medium sized cells with ovoid to spindle shaped nuclei
  • Variable amounts of desmoplasia and myxoid matrix
  • Inactivating SMARCB1 / INI1 alteration
Terminology
  • Desmoplastic myxoid tumor of the pineal region, SMARCB1 mutant
ICD coding
  • ICD-11: 2A00.20 - tumors of the pineal gland or pineal region
Epidemiology
Sites
  • Pineal region
Pathophysiology
  • Precise pathophysiology is unclear
Etiology
  • Precise etiology is unclear
Clinical features
  • Sequelae of obstructive hydrocephalus, such as blurred vision, headache, nausea, vomiting, dizziness
Diagnosis
  • Identification of SMARCB1 / INI1 inactivating alteration and protein loss
Laboratory
  • Serum and cerebrospinal fluid alpha fetoprotein and beta human chorionic gonadotropin are normal
Radiology description
Radiology images

Contributed by Yue-E Wang, M.S., Ph.D., Jingjing Chen, Ph.D., Wei Wang, Ph.D., An-Li Zhang, M.D., Wenchao Zhou, Ph.D. and Hai-Bo Wu, M.D., Ph.D.

MRI - sagittal T1

MRI - sagittal T2

Prognostic factors
  • Prognostic factors are not yet defined but reported prognosis much better than atypical teratoid / rhabdoid tumor
  • 70% of reported patients are alive without recurrence, with a median follow up of 29.5 months (0 months - 7 years) (Neuro Oncol 2022;24:847)
Case reports
Treatment
  • Surgical resection is the treatment of choice
  • Chemotherapy or radiotherapy has been given to a subset of patients (Neuro Oncol 2022;24:847)
Microscopic (histologic) description
  • Epithelioid to spindle shaped cells embedded in a desmoplastic stroma and loose myxoid matrix
  • Rhabdoid cells may be rare
  • No high grade / malignant features such as brisk mitotic activity and tumor necrosis
  • Reference: Acta Neuropathol 2020;139:277
Microscopic (histologic) images

Contributed by Mariana Voudouri, M.D. and George Zanazzi, M.D., Ph.D.

Epithelioid neoplasm with desmoplasia

Cellular atypia

Perivascular tumor cell accumulation

CD34

SMARCB1 / INI1



Contributed by Branavan Manoranjan, M.D., Ph.D., Abdelsimar T. Omar II, M.D., Hai-Bo Wu, M.D., Ph.D., Robert Nordal, M.D. and Yves Starreveld, M.D., Ph.D.

Microcysts and myxoid matrix

Trichrome

Positive stains
Molecular / cytogenetics description
  • Defined by SMARCB1 / INI1 inactivating alterations
  • DNA methylation profile clusters adjacent to atypical teratoid / rhabdoid tumor - MYC and poorly differentiated chordomas
  • Reference: Acta Neuropathol 2020;139:277
Sample pathology report
  • Pineal region tumor, resection:
    • Desmoplastic myxoid tumor of the pineal region, SMARCB1 mutant (see comment)
    • Molecular information: SMARCB1 / INI1 loss of nuclear expression
    • Immunohistochemistry: consistent with mutant
    • Comment: A CNS WHO grade has not yet been assigned to this tumor entity.
Differential diagnosis
Board review style question #1

A 35 year old woman presents with progressively worsening blurred vision, headache, nausea and vomiting. MRI shows a pineal region mass with areas of contrast enhancement. A representative hematoxylin and eosin stained image of the tumor is shown. The tumor cells are CD34 positive and exhibit loss of nuclear SMARCB1 / INI1. The diagnosis is consistent with which of the following?

  1. Desmoplastic myxoid tumor of the pineal region, SMARCB1 mutant
  2. Germinoma
  3. Meningioma, CNS WHO grade 1
  4. Pineocytoma, CNS WHO grade 1
Board review style answer #1
A. Desmoplastic myxoid tumor of the pineal region, SMARCB1 mutant

Comment Here

Reference: Desmoplastic myxoid tumor, SMARCB1 mutant
Board review style question #2
A 28 year old man undergoes resection of a pineal region tumor. A representative hematoxylin and eosin stained section reveals spindled to epithelioid tumor cells embedded in a variably myxoid matrix and desmoplastic stroma. The Ki67 proliferation index is 4%. Which gene would you expect to be mutated?

  1. ATRX
  2. DICER1
  3. EWSR1
  4. SMARCB1
Board review style answer #2
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