Case Study 11Gabrielle Yeaney, M.D.

The patient is a 23-year-old male with headaches, dizziness, anusea, vomiting, diabetes insipidus, and no seizure history.  Hormone studies revealed adrenal insufficiency, hypothyroidism and low IGF-1.

Describe the MRI findings (location, enhancement, etc.).

Question 1

MRI Sagittal T1

MRI Sagittal T1 post-contrast

MRI axial T1 post-contrast

MRI Coronal T1 post-contrast

There is a cystic pineal mass (6 mm) with an enhancing solid component.  The pituitary stalk (infundibulum) is enlarged.

Answer

Question 2Give a differential diagnosis based on clinical history and MRI findings.

Answer Germ cell tumor Pineo-cytoma or -blastoma Lymphoma Metastasis

Rare Stuff Langerhans cell histocytosis Neurosarcoidosis Tuberculosis Infiltrative glioma

Note: Pituitary adenoma and other lesions of the suprasellar variety (craniopharygioma, etc) are not likely in this scenario because of the synchronous involvement of both the stalk and the pineal gland.

Question 3Using endoscopic endonasal approach, the contents of the pituitary stalk are identified.  The surgeon notes a distinct mass within the stalk and gives you a small biopsy.  Describe the cytologic features of the touch preparation.

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AnswerThe touch prep shows a polymorphic population of cells.  There are abundant small lymphocytes and a few plasma cells.  A second cell type consists of large cells each with a single round hyperchromatic nucleus with one or more macronucleoli.  Mitotic figures are present.  The cells on the touch prep are dyshesive.

Question 4What is your intraoperative diagnosis? (A. Neoplastic/Defer/Non-neoplastic, B. ______)

AnswerA. Neoplastic

B. Poorly-differentiated neoplasm, lymphoid-rich; C. Germinoma versus lymphoma--r some variation of the above.

Question 5What additional lab values might be ascertained from the surgeon to help with your diagnosis?

AnswerBlood or CSF levels of alpha-fetoprotein (AFP), beta-human chorionic gonadotrophin or carcinoembryonic antigen if they were drawn.  High levels of AFP imply the presence of yolk-sac tumor, and high levels of beta-HCG suggest choriocarcinoma.

Question 6Review the permanent section.  Describe the histologic features.

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AnswerSheets of large cells showing syncytial growth

Diffuse infiltrate of chronic inflammatory cells (esp. lymphocytes) admixed with tumor cells

Tumor cells are large with vacuolated cytoplasm, vesicular nuclei and prominent nucleoli

Crush artifact

Apoptotic and mitotic figures

Question 7What is your final diagnosis?

AnswerGerminoma

Question 8Tumor cell membranes show reactivity for c-kit (CD117) seen here.  What other immunohistochemical studies might confirm your diagnosis?

Click here to view slide.

AnswerPlacental alkaline phosphatase (PLAP) is usually positive in germinoma but tends to be less "crisp" than c-kit.  OCT4 is sensitive for seminoma, germinoma and embyronal carcinoma.  Syncytiotrophoblasts are reactive for beta-HCG and cytokeratins.  Syncytiotrophoblasts may be seen in germinoma in small numbers and are not necessarily indicative of choriocarcinoma.

Question 9What classic histologic feature would lead you to a diagnosis of yolk-sac tumor (either pure or as a component of a mixed germ cell tumor)?  What immunohistochemical stain is usually expressed in yolk-sac tumors?

AnswerSchiller-Duval body--"endodermal sinus" that looks like a glomeruloid structure; AFP

Question 10What immunohistochemical stain is reactive for embryonal carcinoma?

AnswerCD30

Question 11What other imaging studies should be obtained in this patient (now or follow-up)?

AnswerMRI of spine (to look for drop mets) and MRI/CT of chest/abdomen/pelvis--Metastasis outside of the CNS is rare but can occur.  Abdominal cavity involvement can occur after ventriculoperitoneal shunt placement.  There have been reports of CNS germ cell tumors associated with second lesions in the gonads.

Question 12

What is the prognosis and standard treatment for this neoplasm?

AnswerGerminomas are often curable as they are extremely radio- and chemo-sensitive.  5-year-survival rates are 80-96%.