Usefulness of smears in intra‐operative diagnosis of newly described entities of CNS

Abstract

The recent edition of World Health Organisation (WHO) Classification of Tumours of the Central Nervous System has incorporated a substantial number of important changes. It has recognised several new entities, many of which are rare. Intra-operative diagnosis of these tumours can be difficult with the freezing artefact that often cripples brain frozen sections. In many instances intra-operative smears are extremely useful adjuvants in neuropathological diagnosis. In this article, we describe intra-operative smear findings of three of the newly described tumours. Their characteristic cytologic features are illustrated along with differentiating features from the common mimics, together with a general approach to brain smears. The entities we discuss here are papillary glioneuronal tumour, papillary tumour of the pineal region and angiocentric glioma. All three tumours share at least focal pseudo-papillary/vasculocentric architecture. Smears from papillary glioneuronal tumour demonstrated dual population of cells in a neuropil background, whereas papillary tumour of the pineal region and angiocentric glioma comprise a single population of cells. These two tumours can further be differentiated based on their cell morphology and background.

Papillary tumour of the pineal region

“…The most distinctive feature of its immunophenotype is the strong reactivity for a broad spectrum of CK (including Cam5.2, AE1.AE3, CK18 and KL1). 1,2,[4][5][6][9][10][11][13][14][15][16][17][18]20,21,[23][24][25][26][27][28][29]31 Intense CK18 staining is a consistent finding and this marker is also expressed in the specialised ependymocytes arising from the SCO, which lends further support to the proposed histogenesis of PTPR. 2,10,17,23,24,28,30 CK7, CK20 and CK5/6 are predominantly negative in the minority of cases examined.…”

“…In 60% of the 52 cases examined, EMA has shown variable staining intensity, in a membranous, cell surface, small dot or ring-like distribution, similar to ependymomas. 1,2,[4][5][6][7][12][13][14][15][16][17][18][19][20]24,[26][27][28][29][30][31] Focal immunoexpression of transthyretin may be seen, which has been confirmed on microarray analysis and reverse transcriptase-polymerase chain reaction. 3 Transthyretin is known to be expressed in bovine SCO.…”

“…Strong staining of S100, NCAM, NSE and vimentin is frequently observed. 1,2,4,5,9,10,[12][13][14][15][16][17][19][20][21]24,26,27,29,30 The tumour may exhibit focal or low immunoreactivity for GFAP and neuronal/neuroendocrine antigens, synaptophysin and chromogranin. In 60% of the 52 cases examined, EMA has shown variable staining intensity, in a membranous, cell surface, small dot or ring-like distribution, similar to ependymomas.…”

“…The type of surgical intervention was not described in eight patients. Of the 18 Table 3 Immunohistochemical (IHC) analyses of papillary tumour of the pineal region in previous reports 1,2,[4][5][6][8][9][10][11][12][13][14][15][16][17][18][19][20][21][23][24][25][26][27][28][29][30][31] Intensity of immunoreactivity was scored as: -(absent), + (weak/focal), ++ (moderate) and +++ (strong). patients of whom surgical procedures were documented, the favoured approach for resection was the infratentorial supracerebellar approach (n = 16), and a transcallosal transventricular (n = 2) method was used in only a minority of patients.…”

Angiocentric glioma: the infiltrative glioma with ependymal differentiation

“…Perpendicular arrangement to the pial surface is another helpful feature (1,2,23). Vasculocentric architecture may also be prominent in smear preparations during intraoperative consultation (24). There are 6 cases in the literature with associating cortical dysplasia (6,14).…”