Ssquash smear cytology of CNS, ALgorith to aprroach to squash cytology, new WHO CNS Tumor classification, squash smear preparation

1. SQUASH SMEAR
CYTOLOGY
DR. ANAMIKA DEV

2. INTRODUCTION
• Central nervous system (CNS) is one of the most
challenging domains for the neurosurgeon and
Pathologists
• The application of smear techniques as a means of
obtaining rapid diagnosis for neurosurgical biopsies
was first advocated by Dr Eisenhardt and Dr
Cushing in the USA in early 1930
• Since then, although the technique has been
modified by various individuals by changing the
fixative or stain, the basic principle has remained
unchanged

3. • Simple and rapid methodology for fairly accurate
intraoperative diagnosis of CNS space occupying
lesions.
• High accuracy  clinical and radiological
picture into consideration.
• Two procedures : open craniotomy or
stereotactic biopsy.
• Goal of intraoperative cyto-diagnosis in
stereotactic biopsies to confirm the adequacy
of the tissue.

4. • Use of intraoperative diagnosis in open biopsy:
–Additional tissue for ancillary techniques (for
infections and lymphomas),
–To decide on extent of resection and makes it
possible to institute adjuvant therapy in
immediate postoperative period.
–Last, but not the least, an intraoperative
pathological diagnosis is of great value to the
anxious family members of the patients.

5. SAMPLE IDENTIFICATION
AND TRANSPORTATION
• Transportation - sterile container on a saline-moistened
lens paper or telfa pad (never gauze) to prevent drying
• Request form - relevant clinico-radiologic data
–precise site of biopsy
–reason for which the intraoperative diagnosis was
sought – adequacy or guidance
–technique used : open biopsy, stereotactic-guided
needle aspiration biopsy ; fine-needle aspiration
biopsy

6. HOW TO PREPARE A
SQUASH SMEAR?
• The selected fragment is placed on a glass
slide and then divided into smaller pieces
(1–2 mm3)
• Sample is inspected with the help of a
magnifier or under dissecting microscope to
see whether specimen appears necrotic or
hemorrhagic or both

8. • Each of the smaller pieces is placed on a
newer slide
• A second labelled slide is placed over the
first slide on top of the tissue fragment
• Gently pull both the slides apart to produce
two thin well spread smears

10. • Fixative of choice : 95% Ethanol, 1-2 min
• Additional slides are air dried and stained
• Stain : H&E, Papanicolaou
• additional slides : WRIGHTs stain
• Artifacts : crushing, overstretching and dry
artifacts
• When tissue spreads poorly, stain both slides
with H & E, as one smear will usually have
sufficiently thin areas to make interpretation
possible

11. • Note :
• Don’t smear too large a specimen slide too
thick for optimal cytological detail
• Thin specimen  recognition of fine
fibrillary process often a/w glial tumors
• tissue defy smearing having extensive
reticulin, collagen, or glial fibers

12. COMPARISON OF TISSUE SMEARING
EASILY POORLY
NORMAL BRAIN/ CORD REACTIVE GLIOSIS
MOST PRIMARY /
SECONDARY TUMORS
SCHWANNOMA
NON-NEOPLASTIC
DISORDERS
HEMANGIOBLASTOMA
SUBEPENDYMOMA
DESMOPLASTIC TUMORS
VASCULAR
MALFORMATIONS

14. ADVANTAGES OF SMEAR TECHNIQUE
• Improved cost-effectiveness
• More rapid and technically simpler
• Only small amount of tissue needed
• Far better preservation of cellular detail
• Best in demonstrating fibrillary cytoplasmic processes
• Provides additional information to the permanent sections
• If the case turns out to be infectious, contamination of the
cryostat and subsequent defrosting and sterilization can be
avoided
• Abrogate the risk of distorting valuable diagnostic
material during freezing, which compromise permanent
sections and immunomarkers

15. LIMITATIONS
• Relies on tissue soft enough to smear
• Histologic architecture not apparent
• Relies on accurate localization by the surgeon
• Low-magnification architecture is lost
• Some lesions do not smear well (especially those
having extensive reticulin or collagen)
• Specific training needed (many pathologists are
more familiar with frozen section techniques and
interpretation)

16. • Anaplastic astrocytoma. (a) Cryostat section showing freezing
artifact, nuclear distortion, and effacement of the fibrillary
background (Methylene blue)
• (b) Cytologic preparation from the same tumor showing beautifully
preserved nuclear and cytoplasmic details. Note the characteristic
multipolar astrocytic processes (Smear, H&E)

17. NORMAL CNS
CYTOLOGY

18. NORMAL BRAIN
1. White matter pattern
1. Will smear easily
2. Felt like background
3. Small, empty vacuoles representing dissolved myelin –
scattered in background
4. Cellular population consisting basically of
oligodendrocytes and to a lesser extent of astrocytes
5. Delicate capillaries with elongated endothelial cells
arranged parallel to the capillary wall
6. Also seen few arterioles with thicker walls, in which cells
are arranged parallel (endothelial cells) or perpendicular
(muscle cells) to the lumen - bidirectional arrangement

20. 2. Grey matter pattern
• Smear less evenly than tissue from white matter
• Accumulate elements of larger size, such as blood vessels and
neurons, at the edge of the smear.
• The background is also eosinophilic and granular (feltlike)
• No vacuoles of myelin.
• Numerous neurons seen along with glial cells
• Neurons appear as large cells with abundant cytoplasm,
distinct cell borders, and round, prominent nucleolated nuclei.
• Capillaries of same pattern as white matter
• Also seen arterioles and arteries

22. 3. cerebellar cortex pattern
• More cellular
• Predominant cells  neurons from the internal
granular layer (small, round, hyperchromatic cells
without visible cytoplasm)
• Voluminous Purkinje’s neurons may be observed.
• These cells show a wide cytoplasm with an
expansive dendritic tree and large vesicular nucleus
with a visible nucleolus.

24. 4. Choroid plexus pattern
• A normal choroid plexus may be present in biopsy specimens
from the ventricles
• Vascular-stromal framework tends to smear poorly and
results in a cohesive crush preparation
• Vessels  complex arched papillary appearance,
characteristic of a plexus, lined by a row of cuboidal
epithelial cells
• Cells that appear isolated, due to the squash trauma
– wide polygonal “cobblestone-shaped” cytoplasm
– small, round, basally located nuclei
– Can have single prominent paranuclear cytoplasmic vacuole

26. 5. Leptomeningeal pattern
• Large cell clusters
• The cytoplasm of arachnoid cap cells is wide and
delicate
• Nuclei are round to ovoid with finely granular
dispersed chromatin, often giving the appearance of
central clearings.
• As against cells from the choroid plexus, arachnoidal
cells have poorly defined boundaries, giving rise to
sheets with a syncytial appearance

28. 6. Pineal pattern
• Infant pineal gland preparations
– highly cellular
– uniform, round, single pinealocytes with indistinct
cytoplasm.
– The background is finely granular (neuropil-like) and
calcifications are absent
• Adult pineal gland
– Less cellular, displaying tissue fibrillary fragments and
– single cells with ill-defined cytoplasm and moderate
nuclear pleomorphism
– microcalcifications, referred to as corpora arenacea or
simply “brain sand”

32. NORMAL BRAIN TISSUE PATTERN
AND POTENTIAL MISDIAGNOSIS

33. WHO 2016
CLASSIFICATION OF
CNS TUMORS

42. CNS LESIONS IN WHICH THE
SMEAR TECHNIQUE IS AN
ESPECIALLY USEFUL PROCEDURE
• Astrocytoma
• Oligodendroglioma
• Ependymoma
• Glioblastoma
• Ganglion cell tumors
• Meningioma
• Lymphoma
• Germinoma
• Pituitary adenoma
• Metastases
• Reactive gliosis
• Cerebral infarction
• Inflammatory processes
• Demyelinating disorders
• Cranial and spinal bone
masses

43. APPROACH TO
SMEAR
EVALUTAION

44. APPROACH TO SMEAR
EVALUTAION
• A complete evaluation of the smear requires the
study of six parameters:
1. Type of smearing
2. Type of background
3. Type of blood vessels
4. Presence of specific cell groups
5. Predominant type of cell
6. Presence of specific cellular elements

45. 1.TYPE OF SMEARING
• Normal tissue pattern - uniform/smooth
• Lesional tissue pattern - speckled/granular
Eg : Schwannoma smear reveals only tissue fragments without
single cells.

46. Smear from metastatic
carcinoma showing a
mixed pattern with cell
sheets, smaller cell clusters,
and individual cells.
Smear from lymphoma
showing single cells
without cell aggregates.
Note the numerous
lymphoglandular bodies in
the background

47. 2.TYPE OF BACKGROUND
1. Finely granular (felt like) - normal neuroglial
tissue
2. Clear (empty) - In the case of lesions, if
intercellular space empty
–Schwannoma
–Meningioma
–Pineocytoma
–SFT/Hemangiopericytoma
–Choroid plexus papilloma
–Pituitary adenoma (if imprints)

48. 3. Fibrillary (threadlike)- if intercellular space occupied
by various cell products or components, such as fine
cytoplasmic processes
–Astrocytic tumors
–Ependymal tumors
–Mixed glioneural tumors
–Neuronal tumors (fine neuropil)
4. Necrotic (dirty)
–Necrotic primary tumors - Necrotizing infections
–Radiation necrosis - Necrotic metastasis
–Necrotic CNS lymphoma
–Cerebral infarction

49. 5. GRANULAR-
VACUOLATED
• Released intracytoplasmic
components of a
proteinaceous, lipidic, or
glycogenic nature
• Oligodendroglioma
• Hemangioblastoma
• Demyelinating lesions
• Resolving infarct
• Pituitary adenoma (if
squash/smear)
• Germinoma (“tigroid”)
• Ewing’s sarcoma (“tigroid”)
6. MYXOID/MUCOID
BACKGROUND
• Stromal or mucinous matrix
• Pilocytic/pilomyxoid
astrocytoma
• Myxopapillary ependymoma
• Angiocentric glioma
• DNT
• Neurofibroma
• Chordoma
• Chordoid/myxoid meningioma
• Chordoid glioma
• Gliomas with mucinous
degeneration
• Mucinous metastatic carcinoma

50. • Mixed background
• fibrillary-necrotic background (glioblastoma)
• fibrillary- myxoid background
(pilocytic/pilomyxoid astrocytoma)

51. 3. TYPE OF BLOOD
VESSELS
• Very important in dealing with gliosis
A. Thin-walled
–Low-grade diffuse gliomas (astrocytoma,
oligodendroglioma)
–Neurocytoma
–Dysembryoplastic neuroepithelial tumor.
B. Thick-walled (hyalinized)
–Tumors with degenerative changes
–Schwannoma, ganglioglioma, and pilocytic
astrocytoma, and in the setting of radiation

52. C. Endothelial cell proliferation (microvascular
hyperplasia/ proliferation [MVP])
–Criterion for anaplasia in diffuse astrocytoma and, to
a lesser degree, in oligodendroglioma and
ependymoma, but not in pilocytic astrocytoma.
–MVP occasionally seen in:
• metastatic cancer (mainly small-cell and renal cell
carcinomas)
• nonneoplastic processes (surrounding resolving
infarctions and abscesses).
D. Network of vascular channels
– Intricate network of thin-walled vascular channels
characteristic pattern of hemangioblastoma and
hemangiopericytoma.

53. 1.TUMOR DISTRIBUTION IN
RELATION TO BLOOD VESSELS
A. Perivascular gradient pattern
– Gliomas – especially astrocytoma
B. Angiocentric and diffuse pattern
– Lymphoma
C. Randomised clusters with and without vascular
affinity
– Metastatic carcinoma

55. Glioblastoma: Characteristic microvascular
hyperplasia displaying a “glomeruloid”

56. Diffuse astrocytoma, WHO grade II. Thin-walled,
capillary vessels are usually found in low-grade
diffuse gliomas

57. Hemangiopericytoma. Network of vascular
channels with tumor cell aggregates

58. 4. SPECIFIC CELL GROUPS
1. Whorls
–Meningioma
–Craniopharyngioma
–Epidermoid carcinoma
–Schwannoma
Transitional meningioma.
Typical cell whorls showing
tight concentric
arrangements

59. 2. Papillae
– Choroid plexus tumors
– Papillary/myxopapillary ependymoma
– Papillary meningioma
– Papillary craniopharyngioma
– Papillary tumor of the pineal region
– Metastatic papillary carcinomas
Choroid plexus papilloma.
Characteristic papilla with
a vascular stromal core

60. 3. True rosettes (Flexner-Wintersteiner)
– Ependymoma
– Subependymoma
– ETANTR
– Pineoblastoma
– Medulloepithelioma
Flexner-Wintersteiner
rosettes from
ependymoma, with
prismatic cells
arranged around a
small luminal
structure

61. 4. Pseudorosettes (Homer-Wright)
–Neuroblastoma
–Ganglioneuroblastoma
–Neurocytoma
–Pineocytoma
–PPTID
–Medulloblastoma
–Rosette forming
glioneural tumor
Homer- Wright rosettes
from neuroblastoma,
with central tangles of
fibrillary processes

62. 5. Perivascular pseudorosettes
– Ependymoma
– Astroblastoma
– Subependymal giant cell astrocytoma
– Pilomyxoid astrocytoma
– Papillary glioneural tumor
– Rosette- forming glioneural tumor
– Angiocentric glioma
– Anaplastic astrocytoma
– Glioblastoma

63. Perivascular pseudorosettes from ependymoma,
with tumor cell processes radiating toward a
central vessel

64. 5.TYPE OF CELL
• Glial (fine processes)
• Ganglion/ganglion-like
• Round
• Epithelial/epithelial-like
• Fusiform
• Small poorly differentiated
• Mixed/polymorphic

69. 6.SPECIFIC CELLULAR
ELEMENTS
• Rosenthal fibers
• Eosinophilic granular bodies
• Lymphoglandular bodies
• Keratin
• Melanin
• Mucin

70. clump of Rosenthal fibers and eosinophilic
granular body - pilocytic astrocytoma

71. ROSENTHAL
FIBRES
• Pilocytic astrocytoma
• Ganglioglioma
• Chronic piloid gliosis
• Rosette- forming
glioneural tumor
• Alexander’s disease
E-G BODIES
• Pilocytic astrocytoma
• Ganglion cell tumors
• Pleomorphic
xanthoastrocytoma
• Rosette- forming
glioneural tumor
• DNT (occasionally)

72. Keratin -metastatic epidermoid carcinoma show orange
hyaline cytoplasm with Papanicolaou stain (a) and sky-
blue hyaline aspect with Romanowsky stain (b)

73. KERATIN
• Craniopharyngioma
• Teratoma
• Epidermoid cyst
• Dermoid cyst
• Metastatic epidermoid
carcinoma
LYMPHOGLANDU
LAR BODIES
• Lymphomas
• Non-neoplastic
lymphoid infiltrations

74. Smears from a metastatic melanoma show dark-brown
cytoplasmic granules with Papanicolaou stain and black
granules with Romanowsky stain

75. MELANIN
• Melanoma/
Melanocytoma
• Neurocutaneous
melanosis
• Teratoma
• Pineal anlage tumor
• Melanotic schwannoma
• Melanotic
medulloblatoma
• Melanotic ependymoma
• Melanotic paraganglioma
• Melanotic progonoma
MUCIN
• Mucinous metastatic
carcinoma
• Nonneoplastic cysts of
the neuroaxis
• Glandular component in
teratoma
• Gliomas with mucinous
degeneration

76. (a) Metastatic mucinous colonic adenocarcinoma with abundant thick
mucoid background. (b) Metastatic lung adenocarcinoma displays
numerous intracytoplasmic vacuolar purple granules or “magenta bodies”

78. GLIOSIS
• Reactive astrocytosis or gliosis is a nonspecific
response of the brain tissue
• Neoplastic and nonneoplastic irritating injuries.

79. Reactive gliosis: (a) Clump of evenly spaced reactive astrocytes
and some inflammatory cells (Smear, Romanowsky). (b) Two
stellate-shaped reactive astrocytes with tapering cytoplasmic
processes and mild nuclear enlargement

80. Binucleation (mirror nuclei) and tapering processes radiating
out from all around the cell suggest it is nonneoplastic.
Compare this morphology with the surrounding glioblastoma

81. PILOID GLIOSIS
• Chronic reactive gliosis with abundant Rosenthal fibers
(RFs).
• It is a common process adjacent to cysts and slow-growing
tumors (e.g., pineal cyst, craniopharyngioma,
hemangioblastoma)
• Particularly in the midline axis (third ventricle, brainstem,
cerebellum, and spinal cord)
The long processes forming
a compact layer are
intermixed with numerous
hyaline Rosenthal fibers

82. ASTROCYTIC
TUMORS

83. 1. DIFFUSE ASTROCYTOMA
• Cytologic features-
– Lumpy tissue fragments
– mature capillary vessels
• In comparison with normal brain, smears show:
– Fibrillary (no felt-like) background
– Increased cellularity with uneven cellular distribution
– Mild nuclear atypia
• Gemistocytic variant (at least 20% of the tumor cells)
– Large, plump cells with eccentric nuclei predominate
• Protoplasmic variant
– Small cells with short, cobweb-like processes predominate
– Myxoid background

84. Fibrillary variant - Cellular tissue fragments have uneven, lumpy
appearance, fibrillary background, increased cellularity and mild
nuclear atypia.
(b) Cytoplasms are not discernible and nuclei show irregular
contours and slight hyperchromatism. Vessels are of the
capillary type

85. gemistocytic variant gemistocytic astrocytes with
peripherally displaced nuclei and glassy pink cell bodies

86. protoplasmic variant b)Evenly distributed preparation with small
cells showing round to oval nuclei and sparse cytoplasmic
processes (Smear, Papanicolaou)
(c) Metachromatic myxoid material surrounding the tumor cells
(Smear, Romanowsky)

87. • Diffuse astrocytoma – all 3 variants
– Absence of mitosis
– Absence of microvascular proliferation
– Absence of necrosis,
• Differential diagnosis and pitfalls
– Normal brain tissue
– Reactive gliosis
– Pilocytic astrocytoma
• Gemistocytic variant
– Subependymal giant cell astrocytoma
• Protoplasmic variant
– Oligodendroglioma
– Dysembryoplastic neuroepithelial tumor

88. 2. ANAPLASTIC ASTROCYTOMA
• Cytologic features
– Fibrillary background
– Increased cellularity and pleomorphism
– Distinct nuclear atypia and mitotic activity
– Perivascular aggregates
– Microvascular proliferation and necrosis must be
absent
• Differential diagnosis and pitfalls
– Pleomorphic xanthoastrocytoma
– Pilocytic astrocytoma with degenerative-type atypia
– Anaplastic oligodendroglioma
– Undersampled glioblastoma

89. Dark, elongated and sometimes angulated nuclei without
apparent nucleoli are typical of anaplastic astrocytoma and
glioblastoma, but in WHO grade III tumors, the vessels are still of

90. 3.GLIOBLASTOMA
• Fibrillary and/or necrotic background
• Anomalous vessels
– Microvascular “glomeruloid” proliferation,
– Abnormal fistulous vessels with intraluminal
endothelial proliferation
– Vascular thrombosis
– Pseudopapillary appearance (atypical vessels appear
surrounded by a large number of tumor cells)
• Very high cellularity with discohesive pattern
• Marked cellular pleomorphism with Distinct nuclear atypia
(multilobed appearance, coarse chromatin)
• Often tumor cells conserve fibrillary processes (diagnostic
clue)

91. • Variants/patterns:
– Giant cell (bizarre, multinucleated giant cells predominate)
– Small cell (small, undifferentiated cells predominate)
– Gliosarcoma (mixed pattern of glial and sarcomatous cells)
– Epithelioid (large, epithelioid cells predominate)
• Differential diagnosis and pitfalls
– Other anaplastic gliomas
– Pleomorphic xanthoastrocytoma
– Metastatic carcinoma/melanoma
– Embryonal tumors
– CNS lymphomas
– Sarcomas
– Nonneoplastic necrotic processes
• Necrotizing infections
• Ischemic lesions
• Radiation necrosis with radiation- induced atypia

92. Atypical asytrocytic cells in
fibrillary b/g and giant cells
Necrotic granular debris is
intermixed with ghost cells and
karyorrhectic nuclei

94. 4.PILOCYTIC ASTROCYTOMA
• Fibrillary-myxoid background
• Biphasic cellular pattern:
– Bipolar “piloid” cells
– Multipolar “protoplasmic” cells
• Oval to elongate (piloid) or round (protoplasmic) bland
nuclei
• Rosenthal fibers and eosinophilic granular bodies
• Regressive changes
– Hyalinized/glomeruloid vessels
– Degenerative-type atypia - including large or giant cells
with multiple nuclei circumferentially arranged (“pennies
on a plate”)

95. • Pilomyxoid astrocytoma
– Enhanced myxoid background
– Monomorphous cellular pattern of bipolar cells
– Angiocentric arrangements
– RFs and EGBs typically absent
• Differential diagnosis and pitfalls
– Diffuse astrocytoma (any grade)
– Ependymoma
– Piloid gliosis

96. A) Bipolar “piloid” cells exhibiting very long processes. Nuclei are
bland with smooth contours
B) Brightly eosinophilic Rosenthal fiber with one blunt pole and
one tapered end. It is surrounded by “protoplasmic” cells
exhibiting round nuclei and short, cobweb-like processes

97. a)“pennies on a plate” arrangement
b) angiomatoid vasculature with complex arborization and hyaline
mural fibroplasia, perivascular aggregations of “piloid” tumor cells

98. OLI GODENDROGLI AL
TUMORS

99. OLIGODENDROGLIOMA
• Uniform single cell pattern without adhering to
blood vessels
• Round nuclei with finely granular (salt and pepper)
chromatin and small nucleoli
• Ill-defined, wispy cytoplasm (no perinuclear halos)
• Finely granular/vacoulated or mucoid background
• No fibrillary background
• Delicate branching “chicken-wire” capillary
network
• Microcalcifications

100. • Anaplastic oligodendroglioma
• Increased cellularity and pleomorphism
• Coarser chromatin
• Prominent mitotic activity
• Epithelioid features and minigemistocytes
• Microvascular proliferation

101. • Differential diagnosis and pitfalls
– Diffuse astrocytoma
– Subependymoma
– Dysembryoplastic neuroepithelial tumor
– Pituitary adenoma
– Neurocytoma
– Pineocytoma
– Lymphoma
– Macrophage-rich processes
• Anaplastic oligodendroglioma
– Anaplastic astrocytoma
– Glioblastoma
– Metastatic carcinoma/melanoma

102. a) Uniform population of small, round cells without perinuclear
halos. The background is not fibrillary, but finely granular with
slim capillaries and tiny vacuoles
b)mucoid metachromatic background and a “chicken-wire”
capillary network

103. EPENDYMOMA

104. • Moderately cellular smears
• Fibrillary background
• Dual (glial-epithelial) cellular properties
• Small oval nuclei with stippled chromatin
• Key diagnostic clues
– Perivascular pseudorosettes “arboreal” or “caterpillar”
appearance
– Ependymal rosettes
• Anaplastic ependymoma
– Increased cellularity and coarser chromatin
– Nuclear grooves and indentations
– Mitotic figures and vascular hyperplasia
– Perivascular pseudorosettes
– Fibrillary background
Features retained

105. Classic ependymoma – a) The characteristic branching
“arboreal” appearance of pseudorosettes .Tumor cells
remain tethered to the vessel wall by their glial tails.
(b) High-magnification view showing unevenly distributed
glial cells in a fibrillary background. Nuclei are small, oval,

107. CHOROID
PLEXUS TUMOR

108. • Choroid plexus papilloma:
• Cellular smears with the joint presence of:
– Papillae with fibrovascular cores
– Monolayer fragments
– Single cells
• Columnar to cuboidal cells with:
– Smooth (nonciliated) epithelial surfaces
– Round to oval bland nuclei
• Clean background
• Atypical papillomas:
– Crowded and tall columnar epithelium with the additional
presence of mitoses

109. • Choroid plexus carcinoma
– Malignant cellular characteristics
– Areas of transition papilloma-carcinoma
– Hemorrhagic or granular (necrotic) background
• Differential diagnosis and pitfalls
– Normal choroid plexus
– Papillary ependymoma
– Choroid plexus carcinoma
• Metastatic carcinoma
• Melanoma
• Non-germinomatous (malignant) germ cell tumors
• Atypical teratoid/rhabdoid tumor

110. a)highly cellular preparation has branching papillae, small cell
clusters, and isolated epithelial cells
(b) Papilla with a central vascular core.
c) cell sheets with smooth epithelial surfaces. Nuclei have
slightly coarser chromatin than their normal counterparts but
still lack significant pleomorphism

111. Papillary tissue fragments composed of cells with little
cytoplasm are consistent with choroid plexus carcinoma.
(b) This high-power view shows characteristic vesicular
nuclei with prominent nucleoli and frequent lobulations

112. EMBRYONAL
TUMOR

113. MEDULLOBLASTOMA
• Highly cellular
• Evenly distributed discohesive sheets of small, rounded or
wedge- shaped cells with minimal cytoplasm.
• Nuclei have a slightly coarse “salt-and- pepper” chromatin
and lack nucleoli, nuclear membranes show folds and
indentations
• Medulloblastoma nuclei often stick together forming short
chains or circles or conform around each other, giving the
characteristic nuclear molding

114. Characteristic discohesive pattern of small, round cells with hyperchromatic
nuclei and minimal cytoplasm, nuclear molding. Also a small numbers of
nuclei stick together, forming short chains or circles

115. MENINGIOMA

116. MENINGIOMA
• High cellularity
• Clear background
• Uniform, benign cellular aspect with
–Oval nuclei with delicate chromatin
–Nuclear pseudoinclusions and clearings
–Copious “tissue paper “cytoplasm with broad or
streaked processes
• Cell whorls and psammoma bodies
• Characteristic morphologic variants (fibrous,
secretory, chordoid….)

117. Irregular clusters, small groups, and single cells in a clear
background.
Tumor cells have copious cytoplasm with broad, borderless
processes. Nuclei are slightly oval with frequent intranuclear
pseudoinclusions or clearings (arrows)
Cellular whorls seen

118. Psammomatous meningioma : calcified psammoma bodi

119. Fibrous meningioma. (a) fusiform cells with tapering cytoplasmic
processes. Despite elongation, nuclei show characteristic
meningothelial features including nuclear pseudoinclusions
(b) In contrast to schwannoma, the fusiform cells of fibrous
meningioma tend to appear dispersed with visible cytoplasmic

120. Secretory meningioma. (a) Histology. Numerous intracellular
lumens containing eosinophilic globules are typically (b)
Preparation from this tumor displaying target-like intracytoplasmic

121. Microcystic meningioma :cystic spaces of variable sizes within
the cell clusters and sheets of an otherwise typical meningioma.
The tumor cells exhibit numerous tiny cytoplasmic vacuole

122. Angiomatous meningioma. (a) Histology. Blood vessels constitute
most of the mass. The intervening tumor cells are difficult to
recognize as meningothelial.
(b) Dense network of mature vessels and small clumps of
meningothelial cells with characteristic nuclear pseudoinclusions

123. Metaplastic meningioma. (a) Histology. Presence of
xanthomatous cell aggregates in this case of metaplastic
meningioma.
(b) Large, foamy xanthomatous cells admixed with smaller

124. Pleomorphic meningioma. (a) Some, otherwise, completely benign
meningiomas may show conspicuous nuclear pleomorphism, which
should not be misinterpreted as signifying a potentially aggressive
behavior.
(b) Similarly, the presence of bizarre pleomorphic cells in cytological

125. Atypical meningioma. (a) Hypercellularity, patternless pattern,
and small cell population are characteristic features of this
histologic variant. Mitotic figures seen
(b)discohesive pattern of small, lymphocyte-like cells and many
naked nuclei. Note a nuclear pseudoinclusion

126. Chordoid meningioma. (a) Nests and cords of epithelioid cells in
a basophilic, myxoid-rich matrix characterize this variant.
(b) Undoubted meningothelial cell group embedded in a
metachromatic myxoid matrix. Nuclear pseudoinclusions +

127. Clear cell meningioma. (a) sheets of cells with cleared
cytoplasm due to increased glycogen accumulation and strands
of collagen scattered throughout.
(b) Preparation from this tumor displaying round clear cells with
nuclear features of meningioma

128. Anaplastic meningioma. (a) Histology. Sarcomatous-like
anaplastic meningioma with spindled morphology, poorly
differentiated cytology, and mitosis
(b) Preparation from this tumor showing crowded tissue
fragments and individual cells with anaplastic features

129. Papillary meningioma. (a) The histologic pattern consists of a
perivascular pseudopapillary arrangement of cells on a
vascular-fibrous stroma.
(b) papillary cluster and single cells

130. Rhabdoid meningioma. (a) Tissue section showing an area of
cortical infiltration indicating aggressive tumor behavior. This
variant loses the syncytial appearance of most meningiomas.
(b) Highly cellular preparation with a discohesive pattern of
rhabdoid cells

131. GERM CELL
TUMOR

132. GERMINOMA
• Dual cell population
– Large, primordial germ cells
• Large, spherical nuclei with prominent and
characteristically angular nucleoli. The cytoplasm is
faint, vacuolated, and lacy due to its high glycogen
content
– Small, mature lymphocytes
• Occasionally admixed with plasma cells and
histiocytes.
• Striped “tigroid” background (Romanowsky stains)
– Release of intracytoplasmic glycogen during the squash
– better revealed by using Romanowsky stains
– looks only slightly granular and eosinophilic with H&E or
Papanicolaou stains.
• Frequent granulomatous inflammation

133. a)classic germinoma is made up of sheets of large tumor cells
interrupted by fibrous septae sprinkled with small lymphocyte
b) large germ cells, small lymphocytes, and striped “tigroid”

134. Germinoma pitfall : Tight clusters of epithelioid histiocytes
admixed with a heavy chronic inflammatory infiltrate are
the only feature that appears in this case

135. LYMPHOMA

136. DIFFUSE LARGE B CELL
LYMPHOMA
• The vast majority of PCNSLs (almost 98%) are high-grade
lymphoma of the diffuse large B-cell type (DLBCL)
• Highly cellular smears
• Perivascular cuffing and clearly discohesive cells
• Large, pleomorphic nuclei with prominent nucleoli
• Scant cytoplasm without processes
• Apoptotic bodies and tingible body macrophages
• Granular-vacuolated or necrotic background with LGBs

137. Diffuse large B-cell lymphoma.
(a)A large branching vessel surrounded by atypical cells gives a
clue that this is a lymphoma.
(b)Characteristic single cell pattern of large, atypical lymphoid cells
in a granular-vacuolated background of disintegrating neuropil

138. Discohesive large pleomorphic cells, Numerous
lymphoglandular bodies are typically present in the

139. NERVE SHEATH
TUMOR

140. SCHWANNOMA
• Conventional schwannoma (>90%)
– Very difficult to smear
– Antoni A areas:
• Cohesive tissue fragments without single cells
• Spindle cells with club-shaped nuclei
– Antoni B areas:
• Loosely cellular sheets
• Round to oval nuclei and stellate processes
• Cellular schwannoma (5-10%)
– Only highly cellular Antoni A-type groups
– Mild to moderate hyperchromatism
– Absence of anaplastic features

141. Antoni A zone

142. Antoni B zone- Loose cluster
composed by less regular cells
exhibiting round to oval nuclei
Cellular schwannoma: highly
cellular tissue fragments of spindle
cells, cells are more crowded as
opposed to those in conventional
schwannomas, nuclear uniformity is

143. PITUITARY
ADENOMA

144. • Third most common tumor in the CNS
• Highly cellular smears
• Discohesive monolayer pattern
• Round nuclei with stippled chromatin
• Small “peppery” nucleoli
• Granular background with many bare nuclei
• Plasmacytoid cell appearance
–When cytoplasm is preserved, looks well-
defined with an oval or round morphology
without processes along with the frequent
nuclear eccentric position

145. (a)Discohesive pattern of small cells and numerous bare
nuclei.
(b)Plasmacytoid features with oval cytoplasm and eccentric

146. REFERENCES
• César R. Lacruz, Javier Saénz de Santamaría, Ricardo
H. Bardales, editors. Central Nervous System Intraoperative
Cytopathology. 2nd ed. Switzerland: Springer, 2018.
• Squash preparation; a reliable diagnostic tool in the
intraoperative diagnosis of central nervous system tumors;
journal of cytology/ July 2010/volume 27/issue 3
• Washington manual of surgical pathology
• Internet sources