Fine-Needle Aspiration Cytologyof Primitive NeuroectodermalTumor of the Urinary Bladder:A Case ReportRam Nawal Rao, M.D.,1 Shalu Sinha, M.D.,1

Suresh Babu, M.D.,2 and Ravi Mehrotra, M.D., M.I.A.C., F.A.M.S.3*

Primitive neuroectodermal tumors (PNETs) are malignant smallround cell tumors, which exhibit a variable degree of neural dif-ferentiation. These tumors are usually found in the extraosseoussoft tissue and rarely in bones. Occasional cases of PNETs ofthe urinary bladder have been reported on histopathology. How-ever, to the best of our knowledge, none have been diagnosedon fine-needle aspiration cytology (FNAC). A patient presentedto the out-patient department with complaints of a slowly pro-gressive lump in the lower abdomen, which was diagnosed asPNET on FNAC. The smears showed a dispersed population andsheets of malignant small round cells with focal rosette forma-tion and perivascular arrangement of tumor cells. Periodic acid-Schiff staining showed strong cytoplasmic positivity. Immunocy-tochemistry of the cytology smears also showed strong mem-brane positivity for CD99 (MIC-2), which was also confirmed onhistopathological examination. PNET of the urinary bladder is adistinct entity, which can be diagnosed on FNAC and confirmedby immunohistochemistry. A diagnosis of PNET should be con-sidered as a differential diagnosis in urinary bladder masses,especially in adolescents and young adults. Diagn. Cytopathol.2011;39:924–926. ' 2010 Wiley Periodicals, Inc.

Key Words: neuroectodermal tumor; primitive; urinary bladdermalignancy; aspiration cytology

The common sites of predilection of primitive neuroecto-

dermal tumor (PNET) are soft tissues and bones of chil-

dren and young adults.1–3 These tumors may arise from

any part of the body and can present at any age. They are

closely related to the Ewing’s sarcoma and belong to a

group of a malignant small round cell tumors (SRCTs).

They share the same chromosomal abnormality, i.e.,

(11,22)(q12,q24) involving the EWS gene at 22q12.4 The

histopathological diagnosis of PNET is mainly based on

light microscopic and immunohistochemical examination.

In general, PNET is a very aggressive neoplasm, with

25–50% of the patients presenting with metastatic disease

and a 5-year disease-free survival rate of 45–55%.5,6

PNETs arising in the urinary bladder are extremely rare,

and a literature search revealed eight cases diagnosed on

histopathology till 2009.7–13 To the best of our knowl-

edge, none have been diagnosed on fine-needle aspiration

cytology (FNAC). We describe a rare case of PNET of

the urinary bladder where cytology strongly suggested the

diagnosis, which was later confirmed on histopathology of

the resected mass. Immunocytochemistry (ICC) was per-

formed on aspirated smears and histopathological sections

of the tumor.

Case Report

A 14-year-old girl was admitted to Sanjay Gandhi Post-

graduate Institute of Medical Sciences, Lucknow, India,

with complaints of a slowly progressive lump in the lower

abdomen associated with dull aching pain since 4 months.

Computed tomography and ultrasound examination of the

abdomen revealed a large heterogeneous soft tissue mass

measuring 12 3 9 cm in the pelvis, posterior to the uri-

nary bladder with few irregular areas of calcification.

Ultrasound-guided FNAC was carried out with a 23-gauge

needle and 10-ml syringe. Two passes were performed

from the tumor mass and yielded sufficient material. A

cell block was made from aspirated material. Air-dried

smears were stained with May–Grunwald–Giemsa, two

1Department of Pathology, Sanjay Gandhi Postgraduate Institute ofMedical Sciences, Lucknow, Uttar Pradesh, India

2Department of Pathology, Chatrapati Sahuji Maharaj Medical Univer-sity, Lucknow, Uttar Pradesh, India

3Department of Pathology, Division of Cytopathology, Moti Lal NehruMedical College, Allahabad, Uttar Pradesh, India

*Correspondence to: Ravi Mehrotra, M.D., M.I.A.C., F.A.M.S., MotiLal Nehru Medical College, 16/2 Lowther Road, Allahabad 211002,Uttar Pradesh, India. E-mail: rm8509@gmail.com

Received 28 July 2010; Accepted 29 September 2010DOI 10.1002/dc.21585Published online 3 December 2010 in Wiley Online Library

(wileyonlinelibrary.com).

924 Diagnostic Cytopathology, Vol 39, No 12 ' 2010 WILEY PERIODICALS, INC.

smears were fixed with ethanol for Papanicolaou stain,

and other slides were fixed in acetone up to 2–5 min for

immunocytochemical staining.

Cytology smears were highly cellular and showed

several sheets and dispersed population of malignant

small round cells in a hemorrhagic background. The tu-

mor cells had small round hyperchromatic nuclei, coarse

chromatin, inconspicuous nucleoli, and scanty cytoplasm

with vacuolation, which showed strong Periodic acid-

Schiff-positive staining. Some of the cells had two to

three small nucleoli, occasional rosette formation, and

pseudopapillary patterns (Fig. 1). ICC was performed on

the smears and showed tumor cells with strong membrane

positivity for CD99, weak positivity for neuron-specific

enolase (NSE); however the smears were negative for

leukocyte common antigen (LCA), cytokeratin, chromo-

granin, and desmin A cytological diagnosis of malignant

SRCT of PNET was rendered.

The patient underwent en-bloc resection with sleeve

resection of the bladder. A distended cystectomy speci-

men measuring 15 3 12 3 7.5 cm was received. Outer

surface was nodular. The cut surface showed a necrotic

greyish brown friable growth filling the entire cavity. Nor-

mal bladder mucosa could not be identified.

Histopathological examination of the sections from

resected mass showed cells arranged predominantly in a

pseudopapillary pattern and diffuse sheets (Fig. 2). The

cells had scanty to moderate amount of cytoplasm, round

to oval nuclei, with vesicular to coarse clumped chroma-

tin, and small conspicuous nucleoli. Some of them had

glassy eosinophilic cytoplasm. Frequent mitotic figures,

few rosette-forming structures, and foci of micronecrosis

were also seen. The tumor was seen infiltrating the blad-

der wall mucosa. Resection margins of both ureters were

free from the tumor. Immunohistochemistry was also per-

formed on the histopathology sections from the operated

mass and showed strong positivity for CD99, vimentin,

S100, and weak positivity for NSE. Staining for desmin,

Leucocyte common antigen (LCA), Smooth muscle actin

(SMA), Epithelial membrane antigen (EMA), Human mel-

anoma black 45 (HMB 45), CD117, cytokeratin, synapto-

physin, and chromogranin was negative. The diagnosis of

PNET of urinary bladder on histopathology was thus con-

firmed.

Six months later, the patient had a recurrence of the

lesion with obstructive uropathy. She underwent cystoscopy

and bilateral ureteric stenting. Computed tomography of the

abdomen was done and showed a necrotic enhancing mass

measuring 14 3 12 cm in the pelvis. Ultrasound-guided

FNAC was repeated, and smears showed similar tumor cell

morphology. She received two to three cycles of chemo-

therapy but was lost to follow-up.

Discussion

PNET involving perivesical tissue has been earlier

reported by Hashimoto et al.14 In this report, we have

described a patient of primary PNET of the urinary blad-

der diagnosed by FNAC and confirmed by immunohisto-

chemistry, i.e., CD99, vimentin, and NSE positivity.

PNETs were first described by Stout in 191815 and

include a group of malignant SRCTs that were primitive,

poorly differentiated, highly cellular round cell sarcomas

grouped under the Ewing’s sarcoma/PNETs family of the

tumors.

They were defined by primitive neural features, expres-

sion of the same proto-oncogene, and presence of a bal-

anced t(11,22) (q24,q12) chromosomal translocation that

results in fusion of the EWS gene with FC11 gene or a

Fig. 1. Photograph showing dispersed population of malignant smallround cells in a hemorrhagic background (May–Grunwald–Giemsa,340).

Fig. 2. Histopathology section exhibiting strong membranous CD99immunostaining (H&E, 350). [Color figure can be viewed in the onlineissue, which is available at wileyonlinelibrary.com.]

FNAC OF PNET OF URINARY BLADDER

Diagnostic Cytopathology, Vol 39, No 12 925

Diagnostic Cytopathology DOI 10.1002/dc

chimeric transcripts.16 However, genetic analysis was not

attempted in our patient.

Cytologically, urinary bladder PNETs should be differ-

entiated from other malignant round cell tumors of the

bladder such as rhabdomyosarcoma and neuroblastoma.

Tumor cells express CD99, vimentin, S100, and NSE; a

profile highly suggestive of PNETs. CD99 is almost

always present in these tumors. Neuroblastoma is primar-

ily a tumor of young children, with 90% occurring by the

age of 5 years. The cells in neuroblastoma are seen in a

fibrillary background and show prominent positivity for

NSE and chromogranin and are consistently negative for

CD99.17

Moreover, the lack of staining of LCA (lymphoid),

SMA, EMA (muscle), HMB 45 (melanoma), synaptophy-

sin, and chromogranin (endocrine) markers virtually

excludes the rhabdomyosarcoma, hematolymphoid neo-

plasm, or neuroendocrine carcinoma (particularly in this

age group). PNETs occasionally stain for chromogranin

and synaptophysin, and small cell carcinoma are often cy-

tokeratin positive.18

There are many difficulties in diagnosing SRCTs in

childhood on FNAC samples. First, SRCTs are rare, and

it is difficult for cytopathologists to obtain enough experi-

ence for rendering reliable diagnoses. Second, SRCTs are

morphologically very similar. Third, many SRCTs do not

have specific antigens that could be demonstrated with

ICC, or they lose them when poorly differentiated. In

addition, cross-reactivity exists between some SRCTs.

Unstandardized performance of ICC also contributes to

the difficulties because of unreliable results. Last, subopti-

mal FNAC samples add additional pitfalls, which may be

due to partly degenerate samples or to unrepresentative

ones in cases where a SRCT is a heterologous component

of another nosological entity.19

Two cases of renal PNETs have so far been diagnosed

by FNAC. In these, the smears showed strong membra-

nous immunostaining positivity for CD99 and weak posi-

tivity for NSE.20

The prognosis, in general, is poor.21 Urinary bladder

PNET is a tumor of children and young adults with aggres-

sive behavior. Our patient underwent cystectomy and was

disease-free for 6 months. Then, she developed a recur-

rence of the mass at the same site. She received adjuvant

chemotherapy after diagnosis but was lost to follow-up.

In conclusion, PNETs of the urinary bladder are

extremely rare and aggressive neoplasia; they may be

diagnosed on cytology and diagnosis confirmed with the

aid of immunohistochemistry and cytogenetic studies. A

diagnosis of urinary bladder PNETs must be considered

when interpreting cytologic smears of urinary bladder

masses, particularly in adolescent and young adults spe-

cially in those patients whose tumors demonstrate aggres-

sive clinical behavior.

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