Best Post of August 2012: A case of renal cell carcinoma metastatic to a meningioma

The next in our "Best of the Month" series is from August 9, 2012:

A 74-year-old woman with a history of a seizure disorder had been followed for several years with a stable and unsymptomatic left parasagittal dural-based brain tumor presumed to be a benign meningioma. Recently, though, the lesion increased in size and hemorrhaged, leaving her significantly paretic on the right side. Neurosurgery thereupon performed a craniotomy for tumor removal. Intraoperative frozen section diagnosis was meningioma. But, upon receipt of the permanent sections, I was impressed by the staghorn vessels at low power and hemangiopericytoma immediately came to mind.

Staghorn vessels prominent in region below dot marks

Psammoma body consistent with original impression that this was simply a meningioma

Whirled architecture consistent with meningioma

I was obviously dealing with a meningioma, but something else was going on in that area featuring the staghorn vessels. This region exhibited a different histomorphology:

Clear cells

High-power view of clear cell portion of specimen

This dual morphology puzzled me. I then discovered that back in 2003 the patient had undergone a radical nephrectomy for renal cell carcinoma. Surgical margins of the nephrectomy specimen were free of tumor. I retrieved the 2003 nephrectomy specimen, which looked quite similar to the clear cell portion of the brain tumor:

Nephrectomy specimen from 2003 showing renal cell carcinoma, clear cell type

I thereupon went back to the brain tumor specimen and did some immunohistochemical stains, including RCC for suspected renal cell carcinoma metastasis:

Positive RCC Immunohistochemistry

I had a case of renal cell carcinoma metastatic to a meningioma! Such a case had been reported in the literature before:

Han, HS, et al. Metastatic renal cell carcinoma in a meningioma: a case report. J Korean Med Sci. 2000 October 15 (5):593-597.

Here's case number two!

Follow-up: The patient received radiation to the tumor bed and is recovering.