CAPNON

Case contributed by Assoc Prof Frank Gaillard

Presentation

Headaches.

Patient Data

Age: 65 years
Gender: Male
CT

In the right parieto-occipital region, in line with the parieto-occipital fissure, is a lobulated densely calcified/ossified mass with surrounding edema and a probable anterior perilesional cyst. No appreciable enhancement. 

Old right frontal lobe and bilateral cerebellar hemisphere areas of encephalomalacia. 

No other abnormality. 

MRI

Larger right parietal intra-axial calcified mass measuring up to 3.3 cm in size with an adjacent cystic component measuring 2.5 cm in maximal size. There is only minimal peripheral enhancement of the calcified component and no enhancement of the perilesional cyst (not shown). Associated surrounding edema and surrounding local mass effect with partial effacement of the trigone of the right lateral ventricle.

DWI and brain perfusion imaging are difficult to interpret in the presence of calcification. Spectroscopy is noncontributory (not shown).

Areas of encephalomalacia in the right frontal lobe and cerebellar hemispheres bilaterally, compatible with chronic infarcts. No other suspicious findings elsewhere in the brain.

Conclusion: Heavily calcified right occipitoparietal intraaxial mass with an adjacent cyst, and surrounding edema. The likely differential diagnosis is of a calcified tumor or more likely a CAPNON. 

Pathology

Sections show brain tissue containing a well-circumscribed tumor. The tumor is composed of a hypocellular amorphous-to-fibrillar core. Peripheral "ropey" cords are present. Some osteoid is identified within the tumor. There is a peripheral rind of spindled-to-epithelioid cells at the interface of the tumor with the surrounding brain.

The surrounding brain is gliotic and contains hemosiderin laden macrophages. There is no evidence of malignancy.

FINAL DIAGNOSIS: calcifying pseudoneoplasm of the neuroaxis (CAPNON).

Pathology slides and captions courtesy of Dr Samuel Roberts-Thomson, neuropathologist, Royal Melbourne Hospital. 

Case Discussion

Calcifying pseudoneoplasms of the neuroaxis (CAPNON) are very rare and usually solitary extra-axial masses with a poorly understood etiology. They are considered benign, can occur anywhere in the central nervous system and are frequently overlooked or misdiagnosed, this is an example.

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