The WHO definition of CNS PNETs is that: Tumors composed of undifferentiated or poorly differentiated neuroepihtelial cells which may display divergent differentiation alone neuronal, astrocytic and ependymal lines.
My question is that if a huge tumor located in frontal lobe shows neuroblastic morphology (salt-and-pepper nuclei, rosette, neurofibrillary background ) and immunereativity to CD56 and synaptophysin, cytokeratin and EMA. Would it be appropriate to call it "PNET with unusual cytokeratin immunopositivity? or just call it Neuroendocrine carcinoma? Any help will be greatly appreciated !!
Brain neuroblastoma falls in the category of CNS PNET. And CNS PNET group tumors are not equal to soft tissue and bone PNET. So CD99 should be negative in CSN PNETs.
Here is another picture showing tumor in neurofibrillary background...
In my point of view the pseudorossets (1st photo) and eosinopholic neurofibrillary stroma (2nd photo) suppors the primary CNS nature of tumor (not metastatic neuroendocrine carcinoma). PNET with abberant keratin expression it's a possible diagnosis. What is the age of a patient? Was there any cancer history?
Tumor is the frontal lobe, the possibility of olfactory neuroblastoma exists. Is the olfactory groove involved? What does the MRI report suggest?
Secondly cytokeratin and EMA positivity (dot type) can be seen in PNET.
Neuroblastoma are CD99 negative while PNET are CD99 positive.
As far as metastatic neuroendocrine carcinoma is concerned, does the patient have primary in the lung or anywhere else? If not, this could be olfactory neuroblastoma or PNET depending upon the status of CD99.
Moreover EWS-FLI-1 translocation (-/+) will definitely help.
Brain neuroblastoma falls in the category of CNS PNET. And CNS PNET group tumors are not equal to soft tissue and bone PNET. So CD99 should be negative in CSN PNETs.
The patient is a 48 years-old male with a medical history of nasopharyngeal carcinoma (EBER+) s/p chemotherapy 10 years ago.
The immunohistochemistry profiles are EMA (+), CK (focally+), CD56(+), synaptophysin (focally+), INI-1 (focally +), GFAP (-), CD99 (-/+), S100 (-), TTF-1 (-), EBER (-), KI67 (70%),FLi-1 (+/-), CK7 (focally+) and CK20 (-).
Olfactory neuroblastoma was ruled out according to brain CT and post-op MRI.
The past cancer history, unusual cytokeratin expression, rare age group (CNS PNETs more often affect younger patients) seemed to be against a diagnosis of CNS PNETs.
, or should I call it a metastatic neuroendocrine carcinoma with an "aberrant" neuroblastic morphology?
Is it possible to revise the slides with nasopharyngeal Ca? Maybe there were some neuroendocrine signs?
The original nasopharyngeal carcinoma is postive with EBER CISH, which is lost in the following CNS specimen.
The problem comes to that, A metastatic NPC with neuroendocrine differentiaiton, an aberrant neuroblastic morphology and loss of EBER expression ? or A CNS PNET with an aberrant cytokeratin expression?
Of these two diagnoses, which one makes more sense?
Thanks for the reply!
To Vlad Kropelnytskyi:
No, the nasophargeal tumor is a typical nonkeratinzing squamous cells carcinoma, undifferentiated type.
PNET- supratentorial neuroblastoma
- Mast see IHH for S-100 and NSE
From references-
Iezzoni JC and Mills SE. Undifferentiated smoll round cell tumors of the sinonasal tract. Differential diagnosis Update. Am J Clin Pathol 2005; 124(Suppl 1):110-121
I would not call such a tumour neuroendocrine carcinoma (especially if it' s located in the CNS), but rather PNET with unsual Cytokeratin positivity.
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