Original Article

Cytomorphologic and Clinicoradiologic Analysis of Primary Nonhematologic Central Nervous System Tumors With Positive Cerebrospinal Fluid Cheng-Ying Ho, MD, PhD1; Christopher J. VandenBussche, MD, PhD2; Alison R. Huppman, MD1; Rabia Chaudhry, MD2; and Syed Z. Ali, MD, FRCPath, FIAC2,3

BACKGROUND: Positive cerebrospinal fluid (CSF) cytology typically indicates leptomeningeal dissemination of metastatic, secondary, or rarely, primary central nervous system (CNS) tumors. To the authors’ knowledge, large-scale studies on clinicocytologic features of various primary CNS tumors in CSF are lacking. METHODS: The authors performed a retrospective cytomorphologic study on 127 positive CSF specimens from 87 patients with a history of primary nonhematologic CNS tumors. Pertinent clinical, radiological, and histologic findings were reviewed. RESULTS: Pediatric tumors accounted for the majority (82.6%) of the primary CNS tumors with positive CSF cytology. The most common radiological finding of neuraxial dissemination was diffuse leptomeningeal enhancement. Greater than 95% of the cases with positive CSF cytology were high-grade or malignant tumors. The most common tumor type was central primitive neuroectodermal tumors (47.2%). Overall, the frequency of initial metastasis was found to be lowest in central primitive neuroectodermal tumors and retinoblastomas (approximately one-third). They also had the longest latency (1.5-2 years) in cases without initial metastasis. The majority of metastatic tumors in CSF demonstrated distinct cytomorphology reminiscent of the histologic features of the primary tumor, such as prominent nucleoli, cell wrapping, and apoptosis in large cell/anaplastic medulloblastomas; rhabdoid morphology and cytoplasmic inclusions in atypical teratoid/rhabdoid tumors; large clusters of cells with scant cytoplasm and nuclear molding in retinoblastomas; nuclear pleomorphism and hyperchromasia in highgrade infiltrating astrocytomas; and small clusters/rosettes of epithelioid cells in ependymomas. CONCLUSIONS: The results of the current study provide useful clinicoradiological information and cytomorphologic findings for both common and rare primary CNS tumors that cytopathologists might encounter on CSF examination. Cancer (Cancer Cytopathol) C 2014 American Cancer Society. 2014;000:000-000. V

KEY WORDS: cerebrospinal fluid; cytology; brain tumor; primitive neuroectodermal tumor; glioma; atypical teratoid/ rhabdoid tumor; retinoblastoma.

INTRODUCTION The presence of tumor cells in the cerebrospinal fluid (CSF) often indicates leptomeningeal dissemination of the disease. Positive CSF cytology is frequently observed in extraneural cancer with intracranial or spinal metastasis, but is less common in nonhematologic primary central nervous system (CNS) neoplasms. Overall, only 10% to 20% of patients with primary CNS tumors present with CSF metastasis.1,2 It is interesting to note that positive CSF cytology occurs much more often in pediatric CNS tumors. Previous studies have demonstrated leptomeningeal dissemination in 20% to 30% of children with a history of primary CNS tumors.3,4 Corresponding author: Cheng-Ying Ho, MD, PhD, Division of Pathology, Children’s National Medical Center, 111 Michigan Ave, NW, Washington, DC 20010; Fax: (202) 476-4030; [email protected] 1 Division of Pathology, Children’s National Medical Center, Washington, DC; 2Department of Pathology, The Johns Hopkins Medical Institutions, Baltimore, Maryland; 3Department of Radiology, The Johns Hopkins Medical Institutions, Baltimore, Maryland

The first 2 authors contributed equally to this article. Received: September 10, 2014; Revised: November 17, 2014; Accepted: November 18, 2014 Published online Month 00, 2014 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/cncy.21502, wileyonlinelibrary.com

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1

Original Article

Virtually all types of primary CNS tumors can metastasize to leptomeninges and the subarachnoid space, regardless of the histologic grading. Nevertheless, positive CSF cytology is observed for the most part in malignant embryonal neoplasms such as medulloblastomas, supratentorial primitive neuroectodermal tumors (PNETs), and atypical teratoid/rhabdoid tumors (AT/RTs).3-6 These tumors are known to spread by leptomeningeal extension. Occasionally, CSF seeding can occur in highgrade infiltrating gliomas or ependymomas.3,7 Unlike direct leptomeningeal involvement of embryonal tumors, the mechanism of CSF metastasis in glial neoplasms is believed to be exfoliation of tumor cells into the subarachnoid space.6 As a result of CSF seeding, “drop metastases” can develop throughout the neuraxis. Other less commonly described primary CNS tumors with positive CSF cytology include low-grade neuroepithelial neoplasms,1,8,9 germ cell tumors,1 and choroid plexus tumors.10 Although CSF cytology in conjunction with neuroimaging is the gold standard for detecting the neuraxial spread of CNS tumors, many cases appear to be diagnostically challenging. Cytopathologists often encounter difficulties when interpreting CSF specimens, especially in preoperative evaluation when a histologic diagnosis of the primary tumor has not been established. Due to most pathologists’ unfamiliarity with primary CNS neoplasms, reaching a definitive diagnosis in CSF cytology can be quite difficult. Therefore, large studies covering a broad spectrum of primary CNS tumors with positive CSF cytology are needed to investigate and compare the clinicocytologic features of CSF metastases. In the current bi-institutional study, we performed a comprehensive analysis of 127 CSF specimens with cytologic evidence of metastatic primary CNS tumors. The major objective of the current study was to define unique clinical, radiological, and cytomorphologic features of disseminated primary CNS tumors from a neuropathologist’s perspective.

MATERIALS AND METHODS The current study was approved by the Institutional Review Boards of The Johns Hopkins Hospital (JHH) and the Children’s National Medical Center (CNMC). A database search of the cytopathology archives of JHH from 1990 to 2013 and CNMC from 1988 to 2014 retrieved 127 CSF specimens from 87 patients with pri2

mary CNS tumors. CSF specimens were collected by lumbar, ventricular, or shunt tap. Cytologic material prepared from cytospin or Millipore (Billerica, MA, USA) filter preparations was either air-dried and stained with DiffQuik or fixed in 95% alcohol and stained with Papanicolaou stain or hematoxylin and eosin. Pertinent clinical information, radiological findings, surgical pathology reports, and/or CNS tumor histology slides were reviewed by a subspecialty board-certified neuropathologist (C.H.).

RESULTS The 127 CSF specimens were obtained from 87 patients, including 58 males and 29 females (male:female ratio, 2.0). The age of the patients at the time of the first positive CSF cytology ranged from 1 day (newborn) to 77 years (median age, 7 years). Of the total of 87 patients, 66 were pediatric (aged 18 years; median age at first positive CSF cytology, 4 years) and 21 were adults (median age at first positive CSF cytology, 39 years). Twenty-three CSF specimens were obtained by ventricular tap; 1 specimen was obtained from a shunt; and 103 specimens were collected by lumbar puncture, including 4 preoperative spinal tap specimens. Positive CSF cytology was detected in 27 cases perioperatively or within 1 month of surgery, suggesting that CSF metastasis was present at the time of diagnosis. For cases that did not present initially with metastasis, the latency period from the time of initial surgery to first positive CSF cytology ranged from 1.5 months to 84 months, with a median latency of 13 months. The cellularity of the atypical/malignant cells was variable, ranging from rare (20 cells per slide; 44% of cases). The cellularity did not appear to correlate with the histologic diagnosis of the primary tumor. The size of the tumor cells could be divided into 3 groups: small indicated 5 times the size of a background small lymphocyte or red blood cell. Cytopathologic diagnoses fell into 3 categories: “positive for malignant cells” or “consistent with tumor involvement” (91 cases), “suspicious for malignancy/tumor involvement or markedly atypical cells identified” (19 cases), and “atypical cells identified” (17 cases). At the time of retrospective review of the cases, we believed that this classification simply reflected the original pathologist’s choice of words and did not correlate Cancer Cytopathology

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Analysis of CNS Tumors With Positive CSF/Ho et al

TABLE 1. Demographic and Clinical Information Regarding Primary CNS Tumors With Positive CSF Cytology

Tumor Type cPNET High-grade infiltrating glioma AT/RT LGG or glioma of undetermined grade Retinoblastoma Ependymoma Choroid plexus tumor Germ cell tumor Craniopharyngioma

No. of Patients (%)

No. of Specimens (%)

Sex Ratio (M:F)

Age (Median)a

Lumbar: Ventricular

No. of Patients With Initial Dissemination (%)

Latency, (Median), Monthsb

40 (46) 21 (24)

60 (47) 23 (18)

1.67 3.2

1 d-39 y (5 y) 2 y-77 y (37 y)

50:10 18:5

13 (33) 11 (52)

3-84 (20) 1.5-64 (11)

8 (9) 5 (6)

13 (10) 5 (4)

0.6 1.5

3 mo-4 y (2 y) 4 y-36 y (8 y)

12:1 4:0 (shunt in 1 case)

5 (63) 2 (40)

3-13 (4) 7-38 (9)

1 All male 0.5 All male Male

2 y-5 y (2.5 y) 4 y-18 y (4 y) 7 mo-3 y (3 y) 20 y and 26 y 74 y

7:1 3:0 4:4 2:0 Lumbar

1 (25) 1 (33)c 2 (67) 1 (50) 0

7-54 (17) 13c 15 25 2

4 3 3 2 1

(5) (3) (3) (2) (1)

8 3 8 2 1

(6) (2) (6) (2) (1)

Abbreviations: AT/RT, atypical teratoid/rhabdoid tumor; CNS, central nervous system; cPNET, central primitive neuroectodermal tumor; CSF, cerebrospinal fluid; LGG, low-grade glioma; M:F, male:female. a At first positive cytology. b In cases without initial dissemination. c One patient had no record of surgery.

well with the degree of cytologic abnormalities. The most common histologic diagnosis of the primary tumor was central PNET (cPNET), including 33 medulloblastomas, 6 supratentorial or extracranial PNETs, and 1 pineal anlage tumor. Other primary CNS tumors that presented with positive CSF cytology included high-grade infiltrating gliomas (21 tumors), AT/RTs (8 tumors), low-grade gliomas or gliomas of undetermined grade (5 tumors), retinoblastomas (4 tumors), ependymomas (3 tumors), choroid plexus tumors (3 tumors), germ cell tumors (2 tumors), and craniopharyngiomas (1 tumor). A summary of patient demographics and histologic diagnoses are provided in Table 1. The clinical, radiological, and cytomorphologic findings of each entity are described below in order of decreasing frequency. Central Primitive Neuroectodermal Tumors

In the current study, cPNETs were the most common primary CNS tumors with positive CSF cytology, accounting for nearly one-half of the positive specimens. “cPNET” is a generic term used for malignant small-bluecell neural crest tumors that occur at different regions of the brain, including medulloblastomas, pineoblastomas, and supratentorial PNETs. All cPNETs are aggressive tumors that, unlike most other CNS tumors, frequently metastasize to other brain regions or the spine via CSF pathways. Leptomeningeal dissemination of cPNETs occurs in as many as 30% of medulloblastomas and 25% of supratentorial PNETs at the time of diagnosis.11 The current study identified 33 medulloblastomas, 6 supratenCancer Cytopathology

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torial or extracranial PNETs, and 1 pineal anlage tumor with positive CSF cytology from 40 patients. Twelve patients had recurrent positive CSF cytology. The demographic and clinical information is summarized in Table 1. Testing to detect leptomeningeal dissemination of cPNETs includes neuroimaging and CSF examination. Previous studies have shown a good correlation between positive CSF cytology and positive radiology findings in the diagnosis of metastatic cPNETs.4,11 On gadoliniumenhanced magnetic resonance imaging (MRI), leptomeningeal spread of cPNETs often presented as diffuse (Fig. 1A) or multifocal nodular leptomeningeal enhancement. Cytomorphologic analysis of metastatic cPNETs in CSF revealed medium-sized to large-sized cells, mostly arranged in large spheres (>20 cells) (Figs. 1B and 1C). Occasional cells could be observed to be dispersed singly. Tumor cells had angulated, convoluted, or folded nuclei and coarse chromatin (Figs. 1B-1D). The amount of cytoplasm ranged from scant to moderate, with occasional cells harboring small cell membrane blebs and/or vacuoles (Fig. 1D). Of the 18 medulloblastoma cases with histology available for review, the majority (9 cases) were the large cell/anaplastic (LCA) variants (Figs. 1C and 1D). The rest consisted of 7 classic (Fig. 1B) and 2 desmoplastic/nodular medulloblastomas (Fig. 1E). Severe cytologic atypia such as prominent nucleoli (Fig. 1F), cell wrapping (Fig. 1G), apoptotic bodies (Fig. 1H), and mitosis was more prominent in the CSF of the LCA variant but could also be observed in other histologic variants. Special 3

Original Article

Figure 1. Medulloblastoma is shown. (A) A T1-weighted magnetic resonance image showed a contrast-enhancing medulloblastoma (indicated by “T”) in the cerebellar vermis. Note the leptomeningeal disease presenting as diffuse contrast enhancement within the cerebellar folia, giving it a striped appearance. (B) Classic medulloblastoma cells forming a large cluster and demonstrating cell membrane blebbing are shown. (C and D) Large cell/anaplastic (LCA) medulloblastoma harboring moderate amounts of cytoplasm is shown. (E) Desmoplastic/nodular medulloblastoma is shown. (F) Prominent nucleoli are more frequently observed in the LCA variant. (G) Cell wrapping is shown. (H) Apoptotic bodies are shown (B, C, and E: Diff-Quik stain; D: H & E stain; and F-H: Papanicolaou stain) (B-E: 3400 and F-H: 3630).

caution was needed when interpreting CSF specimens of metastatic medulloblastoma, especially the LCA variant, because in the majority of cases the cytologic features did not resemble the typical small, round, blue cell morphology. 4

High-Grade Infiltrating Gliomas

Leptomeningeal seeding of high-grade infiltrating gliomas, although uncommon in the past, has become increasingly evident in recent years with overall improved survival.12 High-grade infiltrating gliomas, including Cancer Cytopathology

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Figure 2. High-grade infiltrating glioma is shown. (A) A T1-weighted magnetic resonance image of a patient with anaplastic astrocytoma demonstrated diffuse contrast enhancement in the subarachnoid space of the cerebellum (arrowheads). (B) Singly dispersed malignant astrocytoma cells exhibiting hyperchromatic nuclei, amphophilic cytoplasm (similar in color to the adjacent neutrophil), and large perinuclear cytoplasmic vacuoles are shown. (C) Large, multinucleated tumor giant cell is shown that measured >5 times the size of the adjacent neutrophil. (D) A highly cellular cerebrospinal fluid specimen with metastatic glioblastoma is shown. (E) Malignant astrocytoma cells with irregular nuclear contour and visible but inconspicuous nucleoli are shown (B-D: Diff-Quik stain and E: Papanicolaou stain) (B, C, and E: 3400 and D: 3200).

anaplastic astrocytomas (World Health Organization [WHO] grade III), anaplastic oligodendroglioma (WHO grade III), and glioblastomas (WHO grade IV), were the second most common primary CNS tumors with positive CSF cytology noted in the current study. There was only 1 case of anaplastic oligodendroglioma reported; the rest were all malignant astrocytomas. They were detected in 18.1% of the total positive CSF specimens. The specimens were obtained from 12 adult and 9 pediatric patients. Patient demographic and clinical information is summarized in Table 1. Recurrent positive CSF cytology Cancer Cytopathology

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was uncommon in this group (noted in only 2 cases) because the majority of patients (19 of 21 patients) died shortly after the diagnosis of metastasis. Radiographically, leptomeningeal gliomatosis appears as diffuse or nodular contrast enhancement in the subarachnoid space (Fig. 2A). Spinal drop metastasis can occur in high-grade infiltrating gliomas, but are rare.13 Cytologically, metastatic malignant glioma cells were noted to be singly dispersed (Fig. 2B) unless the specimen was highly cellular (Fig. 2D). Tumor cells were medium to large in size and displayed moderate amounts of 5

Original Article

Figure 3. Atypical teratoid/rhabdoid tumor (AT/RT) is shown. (A) A T1-weighted magnetic resonance image demonstrated a contrast-enhancing AT/RT in the left frontal lobe with leptomeningeal thickening and contrast enhancement (pachymeningitislike pattern). (B-D) AT/RT cells displaying rhabdoid morphology, prominent nucleoli, and eosinophilic cytoplasmic inclusion are shown. (B) The morphology resembled histiocytes on Papanicolaou stain (C and D: Diff-Quik stain) (B-D: 3400).

amphophilic cytoplasm. Cytoplasmic vacuolation (Fig. 2B) and multinucleation (Fig. 2C) were frequent. Mitotic figures could be observed occasionally. The nuclei of the tumor cells appeared hyperchromatic with an increased nuclear/cytoplasmic (N/C) ratio compared with background monocytes (Fig. 2B). Nucleoli were visible but not prominent (Fig. 2E). In the CSF, it can be particularly difficult to distinguish malignant glioma cells from monocytes. Based on our observation, glioma cells generally have irregular hyperchromatic nuclei, the cytoplasm is less basophilic, and the cytoplasmic vacuoles are larger in size. Atypical Teratoid/Rhabdoid Tumors

AT/RT is a highly malignant embryonal tumor predominantly manifesting in young children (aged 30 mm) that were Cancer Cytopathology

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noted in a study by Huang et al.6 The discrepancy could perhaps be explained by the relatively small sample size examined in both studies. Low-Grade Gliomas and Gliomas of Undetermined Grade

Leptomeningeal metastasis is considered an uncommon presentation in low-grade gliomas (LGGs). It has been reported in approximately 3% to 6% of pediatric 7

Original Article

Figure 5. Retinoblastoma (Rb) is shown. (A) Diffuse leptomeningeal enhancement accentuating the cerebral and cerebellar sulci as well as outlining the pons is demonstrated. (B) A large cluster of Rb tumor cells displayed nuclear molding (Diff-Quik stain, 3400).

cases.8,16,17 Patterns of dissemination appear to be related to the primary site: hypothalamic tumors metastasize via the ventricular CSF pathways, whereas tumors in other locations disseminate along subarachnoid pathways.8 In the current study, we identified 4 LGGs and 2 gliomas of undetermined grade (1 astroblastoma and 1 inoperable diffuse intrinsic pontine glioma) with positive CSF cytology. The LGG cases included diffuse astrocytoma (WHO grade II), pilocytic astrocytoma (WHO grade I), and subependymal giant cell astrocytoma (SEGA) (WHO grade I). The pilocytic astrocytoma case arose from the hypothalamus/ optic chiasm, whereas the diffuse astrocytoma and SEGA were both located in the periventricular region. CSF of the pilocytic astrocytoma case was collected from the shunt. The patient with diffuse astrocytoma and the patient with pilocytic astrocytoma both died of disseminated disease. Both cases had only radiology reports available for review. On cytologic examination, the disseminated pilocytic astrocytoma appeared as moderately cellular glial tissue fragments with elongated nuclei and bland cytology (Fig. 4A). Without clinical history and radiological findings, the specimen would be essentially indistinguishable from normal brain tissue on morphologic grounds. The SEGA case presented as a large, lateral, intraventricular mass on the MRI (Fig. 4B). There was no abnormal enhancement in the subarachnoid space to suggest dissemination of the disease. On CSF examination, SEGA appeared as individual atypical cells with abundant, amphophilic, vacuolated cytoplasm and irregular 8

nuclei. The cytomorphology of SEGA cells was similar to that of high-grade glioma cells except for the low N/C ratio (Fig. 4C). Cytologic slides of the diffuse astrocytoma cases were not available for review. Given the rarity of CSF metastasis in patients with LGGs, cytologic findings should always be interpreted in the appropriate clinical and radiological context. Cytologic interpretation requires extra caution in ventricular CSF specimens, which can contain normal CNS tissue dislodged by the procedure. Retinoblastoma

Retinoblastoma (Rb) is a malignant eye tumor that most commonly affects young children. According to the American Joint Committee on Cancer pathological classification system,18 CSF metastasis of Rb is considered pM1e. It is an uncommon but often fatal event. We identified metastatic Rb in 8 CSF specimens from 4 pediatric patients. One case had an initial presentation of CSF metastasis, and the diagnosis was in fact rendered on CSF cytology. The other 3 cases displayed a relatively long latency period of 7 months, 17 months, and 54 months, respectively. Two patients had recurrent positive CSF cytology (Table 1). Radiologically, disseminated Rb presented as diffuse leptomeningeal enhancement involving the cerebrum, cerebellum, and brainstem (Fig. 5A). CSF cytologic analyses revealed highly cellular specimens comprised of frequent large clusters (>20 cells) of atypical cells. Tumor Cancer Cytopathology

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ependymomas on CSF examination in 2 young children (both aged 4 years) and 1 teenager (aged 18 years). One tumor was located in the posterior fossa, whereas 2 other tumors were supratentorial. Only the supratentorial tumors had histology that was available for review, and both were anaplastic ependymomas (WHO grade III). Although the radiology images were not available for review, the radiology reports mentioned no evidence of metastatic or disseminated disease. On cytomorphologic examination, ependymoma cells displayed a tendency to aggregate into vague rosette formations or small 3-dimensional clusters (Figs. 6A and 6B). The cells were small to medium in size and contained uniform oval nuclei with smooth nuclear contour and finely granular chromatin. Some cells exhibited epithelioid morphology (Fig. 6A). Despite the malignant histologic classification, the overall cytologic features of metastatic anaplastic ependymomas in CSF were fairly bland compared with high-grade infiltrating gliomas. Choroid Plexus Tumors

Figure 6. Ependymoma is shown. The cytology was bland even though the tumor was histologically classified as anaplastic/malignant (World Health Organization grade III). (A) Tumor cells with epithelioid morphology are shown. (B) Tumor cells are noted in a vague rosette formation (A and B: Papanicolaou stain, 3400).

cells were medium to large-sized, with scant to fair amounts of light to royal blue cytoplasm, angulated nuclei, and indistinct or absent nucleoli (Fig. 5B). Features of a “small blue round cell tumor,” such as an increased N/C ratio and nuclear molding (Fig. 5B), appeared to be slightly more prominent in Rbs compared with cPNETs in CSF. Ependymomas

CSF dissemination of ependymomas at the time of diagnosis is rare but is somewhat more common with highergrade tumors.19 In the current study, we found metastatic Cancer Cytopathology

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Choroid plexus tumors account for approximately 3% of primary brain tumors diagnosed in children. They can be further classified into choroid plexus papilloma (CPP) (WHO grade I), atypical choroid plexus papilloma (WHO grade II), and choroid plexus carcinoma (CPC) (WHO grade III) based on mitotic activity and other histologic features. Disseminated CPC is present in 45% patients at the time of diagnosis and is associated with a poor prognosis.10 CPPs, conversely, are generally regarded as benign tumors and rarely metastasize.20 In the current study, there were 8 specimens of choroid plexus tumors obtained from 3 young pediatric patients (a 7-month-old infant and 2 children aged 3 years) that demonstrated positive CSF cytology. Histologic diagnoses included 2 cases of CPC and 1 case of CPP. The possibility of procedure-related tumor shedding could not be excluded from the CPP case, and therefore the cytologic finding might not reflect tumor seeding. Both patients with CPCs demonstrated recurrent positive CSF cytology (Table 1). All 3 cases had only radiology reports available for review and did not demonstrate radiological evidence of metastatic or disseminated disease. Disseminated CPC in the CSF was comprised of variably sized tissue fragments in a papillary or rosette formation. Tumor cells displayed hyperchromasia, nuclear 9

Original Article

Figure 7. Choroid plexus carcinoma (CPC) is shown. (A) A fragment of CPC in papillary formation is shown. Note the variability in cell size. (B) A fragment of epithelioid cells is shown. (C) Large cells with hyperchromatic nuclei are noted (A-C: Papanicolaou stain; A: 3200; B and C: 3400).

pleomorphism, and an increased N/C ratio. Nucleoli were occasionally visible but not prominent (Figs. 7A-7C). Germ Cell Tumors

We identified 2 cases of disseminated intracranial germ cell tumors in 2 young adult male patients aged 20 years and 26 years, respectively, at the time of positive CSF cytology. One tumor was located in the pineal gland and the other was noted in the suprasellar region. The histologic diagnosis of the pineal gland tumor was germinoma. However, the elevation in the serum a-fetoprotein level suggested a possible yolk sac component. The histology of 10

this case was not available for review. The suprasellar tumor was a pure germinoma. One patient presented with initial metastasis, whereas the other patient had a latency period of 25 months. The MRI of the pineal tumor demonstrated extensive leptomeningeal nodular enhancement throughout the entire neuraxis (Fig. 8A). Conversely, the suprasellar tumor did not have radiological evidence of disseminated disease. Cytologic examination of the CSF revealed cohesive or syncytial clusters of monomorphic, medium-sized to large-sized cells with irregular, centrally located nuclei (Fig. 8B). One or 2 nucleoli were commonly observed in tumor cells (Fig. 8B). Cancer Cytopathology

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Figure 8. Germinoma is shown. (A) A T1-weighted magnetic resonance image demonstrated extensive multinodular leptomeningeal contrast enhancement in the cerebellum. (B) Tumor cells with large central nuclei and 1 or 2 conspicuous nucleoli are noted (Papanicolaou stain, 3400).

Craniopharyngioma

We had a case of craniopharyngioma diagnosed in a 74year-old man whose 2-month postoperative lumbar tap demonstrated nucleated squames. Because there was no evidence of tumor dissemination on imaging, the clinical significance of the squame shedding was unclear. However, the patient died a few months after the positive CSF cytology.

DISCUSSION Detection of tumor cells in the CSF indicates dissemination of primary CNS neoplasms in the subarachnoid space and is predictive of a poor outcome. The early diagnosis of leptomeningeal disease can be crucial because the institution of aggressive treatment, such as radiotherapy, may increase a patient’s chance of survival. Although CSF analysis is the standard diagnostic modality with which to detect leptomeningeal spread of a tumor, the interpretation of CSF cytology can be quite challenging. Given the relatively low frequency of metastatic primary CNS tumors in the CSF and the low cellularity of most specimens, the clinical history and radiological findings appear essential for making the proper diagnosis. To the best of our knowledge, the current study is the largest and most comprehensive study to date analyzing 127 CSF specimens with positive cytology of primary CNS tumors. The positive cases accounted for 2.8% of the total CSF specimens at CNMC and 0.4% of the total Cancer Cytopathology

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CSF specimens at JHH. Pediatric tumors accounted for the majority of the cases with positive CSF cytology (82.6%), even in the multispecialty hospital (JHH) (73.2%), at which the majority of patients are adults. The most common radiological finding indicative of neuraxial dissemination was diffuse leptomeningeal enhancement (Figs. 1A and 5A), although nodular (Fig. 8A) and pachymeningitis-like (leptomeningeal thickening) (Fig. 3A) enhancement as well as negative radiology (Fig. 4B) also were encountered in the current study. The radiographic patterns did not appear to correlate with tumor types. However, the intraventricular neoplasms, such as ependymomas, choroid plexus tumors, and SEGAs, did appear to account for the majority of the discordant cases (positive cytology with negative radiology). In the current study, >95% of the primary nonhematologic CNS tumors with positive CSF cytology were high-grade or malignant. Cytologic interpretation of CSF dissemination in low-grade tumors needs to be scrutinized, especially in ventricular specimens that possibly contain contaminating tumor or normal tissue dislodged by the procedure. The most common tumor type to cause positive CSF cytology was cPNET, which included medulloblastomas (posterior fossa), pineoblastomas, and supratentorial PNETs. Overall, cPNETs and Rbs demonstrated the longest latency between the time of diagnosis of the primary tumor and first positive CSF cytology. Approximately two-thirds of cases had no initial metastasis and demonstrated a median latency period of 1.5 to 11

Original Article TABLE 2. Summary of Cytomorphologic Characteristics of Disseminated Primary CNS Tumors in CSF Cell Sizea

cPNET

Medium to large

Large

Fair to moderate/ light to royal blue

High-grade infiltrating glioma

Medium to large

Moderate/ amphophilic

AT/RT

Medium to large

Variable (cellularity dependent) Singly to small

LGG or glioma of undetermined grade Retinoblastoma

Variable

Variable

Medium to large Small to medium

Large

Choroid plexus carcinoma

Variable

Germ cell tumor

Medium to large

Variably sized fragments or clusters Variable

Ependymoma

Clustersb

Cytoplasm: Amount/Colorc

Tumor Type

Small to medium

Moderate to abundant/ amphophilic Variable depending on tumor type Scant to moderate/ light to royal blue Scant to moderate/ amphophilic Scant to moderate/ amphophilic Moderate/light blue to amphophilic

Nuclear Features Angulated, convoluted with coarse chromatin and occasional prominent nucleoli Irregular, hyperchromatic, " N/C ratio, pleomorphic, multinucleated Eccentrically located

Variable depending on tumor type Angulated, "N/C ratio Oval, smooth with finely granular chromatin

Hyperchromatic, "N/C ratio, pleomorphic Centrally located, occasional prominent nucleoli

Other Cytomorphologic Features Small membrane blebs, small cytoplasmic vacuoles, cell wrapping, apoptosis, and mitosis Medium to large cytoplasmic vacuoles, mitosis Rhabdoid morphology, eosinophilic cytoplasmic inclusion Variable depending on tumor type Nuclear molding Epithelioid morphology, vague rosette or 3dimensional cluster formation Papillary architecture

Cohesive or syncytial clusters

Abbreviations: AT/RT, atypical teratoid/rhabdoid tumor; CNS, central nervous system; cPNET, central primitive neuroectodermal tumor; CSF, cerebrospinal fluid; LGG, low-grade glioma; N/C, nuclear/cytoplasmic. a Small: 5 times the size of a small lymphocyte or red blood cell. b Most frequently observed pattern: small: 20 cells. c On Diff-Quik stain.

2 years. In comparison, dissemination of AT/RTs occurred early, with an initial CSF metastasis rate of 62.5% noted among disseminated tumors. Cases without initial metastasis had a short median latency of 4 months. Metastatic high-grade infiltrating gliomas also had >50% of cases presenting with initial metastasis. The latency was between that of AT/RTs and cPNETs/Rbs (11 months). The sample size of other tumor types was too small to draw meaningful conclusions regarding the latency. However, the overall latency to CSF involvement is generally much shorter than the latency to extraneural spread, which is much more rare and may be 10 years.21 The cytomorphologic findings are summarized in Table 2. The majority of the CSF specimens were obtained postoperatively when patients already had an established histologic diagnosis of the primary tumor. Therefore, the diagnostic challenge was mainly to distinguish tumor cells from background hematologic elements (especially monocytes) rather than to classify the tumor type. The majority of metastatic tumors in CSF demonstrated distinct cytomorphology reminiscent of the histologic features of the primary tumor. This included 12

prominent nucleoli, cell wrapping, and apoptosis in LCA medulloblastomas; rhabdoid morphology and cytoplasmic inclusions in AT/RTs; large clusters of cells with scant cytoplasm and nuclear molding in Rbs; nuclear pleomorphism and hyperchromasia in high-grade infiltrating astrocytomas; and small clusters/rosettes of epithelioid cells in ependymomas. In most instances, cytomorphologic analysis with clinical and radiological correlations was sufficient to diagnose CSF metastasis. Based on our experience, cell blocks were of limited use because immunohistochemical studies failed to improve diagnostic accuracy. It is interesting to note that we encountered 6 cases for which the cytologic diagnoses were rendered preoperatively or without a histologic diagnosis (surgery not performed). The 4 preoperative specimens included 2 AT/ RTs, 1 high-grade astrocytoma, and 1 SEGA. The 2 inoperable cases were an Rb and a pontine glioma. Given the overtly atypical cytomorphology of AT/RT and Rb cells, a cytologic diagnosis of malignancy was easily established for all 3 cases. Conversely, the glioma cases appeared more challenging due to the low tumor volume and similarities Cancer Cytopathology

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in cell size between tumor cells and background monocytes. These cases were interpreted as “atypical.” The results of the current large, bi-institutional study provide a comprehensive clinical, radiological, and cytomorphologic analysis of primary nonhematologic CNS tumors with positive CSF cytology. Useful information and illustrations have been provided from a neuropathologist’s perspective to help cytopathologists become familiar with common and rare entities that might be encountered on CSF examination.

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FUNDING SUPPORT

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No specific funding was disclosed. 14.

CONFLICT OF INTEREST DISCLOSURES The authors made no disclosures.

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Cytomorphologic and clinicoradiologic analysis of primary nonhematologic central nervous system tumors with positive cerebrospinal fluid.

Positive cerebrospinal fluid (CSF) cytology typically indicates leptomeningeal dissemination of metastatic, secondary, or rarely, primary central nerv...
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