Case Study 12Gabrielle Yeaney, M.D.

19-year-old man with a past medical history of ALL who presents with a several week history of intermittent falls secondary to his legs giving out on him.  He also describes sensory changes in his legs bilaterally.

Describe the MRI findings (location, enhancement, mass effect).

Question 1

MRI sagittal T1 w/o and w/contrast

MRI axial T2

MRIs show an enhancing intradural, extramedullary mass at the thoracic (T6-T7) level on the right side extending through a neural foramen causing compression of the spinal cord.

Answer

Question 2What is in the differential diagnosis of an intradural, extramedullary spinal lesion?

Answer Schwannoma

Meningioma

Hemangiopericytoma

Solitary fibrous tumor

Melanocytic neoplasm

Inflammatory / infectious (sarcoidosis, TB)

Vascular malformation

Mesenchymal chondrosarcoma

For this case specifically, you could include chloroma since the patient has a history of ALL, but it would be unusual.

Question 3You are called for an intraoperative consultation.  A squash preparation is performed.  Due to the firmness of the tissue, a frozen section is also done.  What is your intraoperative diagnosis? (A. Neoplastic/Defer/Non-neoplastic, B. ________)

Click here to view slides.

AnswerA. Neoplastic

B. Schwannoma

Question 4Review the permanent section.  What are the classic architectural features seen in this neoplasm?

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AnswerThis classic biphasic pattern is shown with compact (Antoni A) and loose (Antoni B) areas.  Verocay bodies, foci with nuclear palisading, are present in Antoni A areas.

Question 5Sometimes this tumor can appear histologically similar to fibrous meningioma or tanycytic ependymoma, given the cellular elongation and spindled patterns in all.  What immunohistochemical stains would you use to differentiate the neoplasms?  Give a panel of at least 3 markers and state whether positive or negative.

AnswerAn immuno-panel including S100, epithelial membrane antigen (EMA) and glial fibrillary acidic protein (GFAP) would be useful.  The following staining patterns are expected: meningioma (S100 -, EMA +, GFAP -); ependymoma (S100 +, EMA may have focal dot-like cytoplasmic reactivity, GFAP ++ especially in pseudorosettes); schwannoma (S100 ++, EMA -, GFAP may have patchy reactivity).  Schwannomas have more reticulin fibers (not an immunostain) and stronger expression of collagen IV and laminin than tanycytic ependymomas.

Question 6What is "ancient change"?

AnswerAncient change is nuclear pleomorphism and hyperchromasia and is frequently seen in schwannomas.  This "atypia" represents a degenerative phenomenon rather than a true neoplastic atypia/anaplasia, as it is not associated with cell proliferation. Schwannomas can have vascular hyalinization, stromal myxoid change and cystic change.

Question 7What hereditary disease is associated with finding multiple tumors like this?

AnswerNeurofibromatosis 2 (central neurofibromatosis) is an autosomal dominant disorder associated with schwannomas.  The NF2 gene is found on chromosome 22q12, and its gene product is merlin, or schwannoma.  Bilateral vestibular schwannomas and/or meningiomas, multiple cutaneous/craniospinal schwannomas, glioma, lens opacity (cataract) are associated.

Question 8True or False. In general, malignant peripheral nerve sheath tumors arise from this neoplasm.

AnswerFalse. MPNST is a malignant tumor arising from or differentiating towards cells intrinsic to peripheral nerves, but it should nto be viewed as a malignant counterpart to schwannoma.  True malignant schwannomas are exceedingly rare.  MPNSTs are often seen in association with NF1 (von Recklinghausen disease), and half of MPNSTs are derived from neurofibromas.

Question 9What is the prognosis and standard treatment for this neoplasm?

AnswerMost classic schwannomas are cured surgically.