Cystic lesions of the pineal region - MRI and pathology

Abstract

Pineal lesions are rare. Tumours in this location comprise 0.4-1% of intracranial tumours. They grow mainly as solid-mass lesions, and cystic tumours are not common. On MRI, a cystic configuration is associated usually with non-neoplastic pineal lesions rather than with a tumour, but analysis does not allow cystic pineal tumours to be distinguished from glial cysts with certainty. We compared neuroradiological and pathological data from 13 cystic pineal lesions, analysing preoperative MRI. Formalin-fixed, paraffin-embedded surgical specimens were stained routinely and immunocytochemically, using the streptavidin-biotin-complex method. Histology revealed six pineocytomas, four glial cysts, an arachnoid cyst, a low-grade astrocytoma and a teratoma. Signal characteristics of pineocytomas were similar in many respects to those of glial pineal cysts. Histomorphological analysis allowed unambiguous discrimination between pineocytomas and glial pineal cysts.

Pineocytoma Mimicking a Pineal Cyst on Imaging: True Diagnostic Dilemma or a Case of Incomplete Imaging?: Fig 1.

“…It has been previously reported that pineocytomas can mimic typical pineal cysts in imaging appearance [1][2][3][4][5][6][7][8][9][10][11][12][13] ; it has been our experience, however, that when fully and completely imaged-which necessitates using postcontrast MR imaging-most of these tumors bear little resemblance to typical pineal cysts.…”

“…No information was provided regarding the specific type of gadolinium-based contrast used, volume of contrast, or time elapsed between contrast administration and imaging. 5,14,[18][19][20][21][22] Only a single reviewed study provided information regarding CT scanning parameters, though even then specific information on scanner type was not provided. In that study, 10-mm sections were obtained in the supratentorial region, and 5-mm sections, in the infratentorial region, using 200 -275 mAs and 100 -120 KV(p), with a 512 ϫ 512 matrix.…”

“…The first described 6 pineocytomas that were primarily cystic. 5 One was septate and eccentric with a thick wall, 1 had a dorsal nodule, 3 had walls that were thicker than 2 mm (more precise measurements were not provided), whereas 1 may have been a simple cyst with a thin wall (it is difficult to determine this from the published data). Unfortunately, specific information regarding wall thickness, specifically whether the enhancing wall was greater or less than 2 mm, was not provided, nor were images provided for independent review.…”

“…In some cases, the appearance may be similar to a pineal cyst, and differentiation between these entities may not be possible. [1][2][3][4][5][6][7][8][9][10][11][12][13] Pineal cysts are benign cystic lesions identified in 1%-4% of MR images of healthy subjects.…”

“…Therefore, these lesions are often followed up with multiple imaging studies to document stability, and, at times, surgical intervention is even considered to obtain a definitive diagnosis. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] It has been reported that on delayed imaging (60 -90 minutes after gadolinium injection), contrast material may diffuse from the enhanced rim into the fluid center of the pineal cyst, producing an increasingly homogeneous enhancement pattern, suggestive of solid neoplasm. 12,14,17 Therefore, it is important to take into account the time elapsed after contrast administration in such unusual cases.…”