PRIMITIVE NEUROECTODERMAL TUMOR OF THE PROSTATE

MICHAEL PEYROMAURE,* ANNICK VIEILLEFOND, ERIC BOUCHER, GONZAGUE DE PINIEUX,PHILIPPE BEUZEBOC, BERNARD DEBRE AND THIERRY A. FLAM

From the Departments of Urology (MP, BD, TAF), Pathology (AV, EB, GdP) and Medical Oncology (PB), Cochin Hospital, Paris, France

KEY WORDS: prostatic neoplasms; neuroectodermal tumors, primitive; sarcoma, Ewing’s

We report a primitive neuroectodermal tumor (PNET) ofthe prostate. Treatment consisted of chemotherapy followedby cystoprostatectomy and adjuvant external beam radiationtherapy.

CASE REPORT

A 27-year-old man presented with dysuria and pelvic dis-comfort. Physical examination revealed a palpable suprapu-bic mass extending above the umbilicus. Digital rectal exam-ination demonstrated a firm pelvic mass, consistent with alocally advanced prostatic tumor. The patient had no mani-festation of a paraneoplastic syndrome. Computerized tomog-

raphy and magnetic resonance imaging (MRI) confirmed thepresence of a giant pelvic tumor below the bladder (fig. 1).Prostatic biopsies showed sheets of uniform small round bluecells, without glandular prostatic tissue (fig. 2, A). Immuno-histochemical study revealed diffuse staining with anti-CD99antibody (fig. 2, B). The cells were negative for all otherantibodies tested, including anti-keratin, CD45, smooth mus-cle actin, desmin, S-100 protein, chromogranin A and neuronspecific enolase. Testing for Ewing’s sarcoma/PNET fusiontranscripts by reverse transcriptase polymerase chain reac-tion performed on frozen tissue demonstrated the transloca-tion t(11;22)(q24;q12), thus, confirming the diagnosis ofPNET.

The patient received multiagent chemotherapy (6 coursesof vincristine, ifosfamide, doxorubicin and etoposide). Che-motherapy resulted in a significant decrease in tumor size,and was followed by cystoprostatectomy and replacementileocystoplasty. Pathological examination showed diffuseprostatic PNET at the base of the gland only, with extensioninto the bladder neck and vascular invasion. There was noextracapsular extension except at the base of the prostate,and seminal vesicles were normal. Approximately 70% of theprostatic tissue was replaced by necrosis. The patient thenreceived pelvic external beam radiation therapy at a dose of40 Gy. Two months later clinical examination was normaland MRI revealed complete remission of the tumor.

DISCUSSION

PNET, or extraskeletal Ewing’s sarcoma, is a rare variantthat mostly occurs in children and young adults, and isassociated with a poor prognosis. The primary tumor origi-nates from soft tissue in the majority of cases.1 Microscopi-cally, it is characterized by primitive round cells stronglyreactive to anti-CD99 antibody (monoclonal antibody 013).CD99 positivity distinguishes PNET from other rare entitiessuch as lymphoma, rhabdomyosarcoma and neuroendocrinecancer.1 In some cases cytogenic analysis is helpful to con-firm the diagnosis. Indeed, more than 90% of PNETs demon-strate a translocation between the long arms of chromosomes11 and 22, which is pathognomonic for this family of tumors.1

Accepted for publication February 14, 2003.* Corresponding author: Service d’Urologie, Hopital Cochin, 27 rue

du faubourg Saint-Jacques, Paris, France.

FIG. 1. MRI shows giant pelvic tumor below bladder (sagittal view)

FIG. 2. A, diffuse sheets of small round blue cells. B, strong membranous staining of tumor cells with anti-CD99 antibody (HBA 71). H &E, reduced from �400.

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Therefore, the diagnosis may be established by either immu-nohistochemical evaluation or chromosomal analysis identi-fying the specific translocation t(11;22)(q24;q12).

Visceral localizations are unusual, with kidney being themost commonly cited.1 Several cases of other visceral local-izations have been described, including pancreas, parotidgland, small bowel and bladder.2, 3 Most of these tumors weresuccessfully treated with local therapy (surgery followed byradiation therapy) and chemotherapy.2 Only 1 known case ofPNET of the bladder has been reported in the literature.3

Treatment consisted of partial cystectomy followed by mul-tiagent chemotherapy. The patient was disease-free 18months after treatment. To our knowledge no case of PNEToriginating from the prostate has been reported previously.

Little information is available regarding the therapeuticoptions for such tumors, and the currently recommendedtreatment is based on chemotherapy followed by surgicalresection and radiotherapy.2 Our patient received the vin-cristine, ifosfamide, doxorubicin and etoposide protocol,

which is widely used in Ewing’s sarcomas, and adjuvantradiation therapy to decrease the risk of local recurrence.Using multiagent chemotherapy and radiotherapy, morethan 50% of patients with localized disease remain disease-free at long-term followup.2 However, the most appropriatetreatment for this rare entity is still debatable.

REFERENCES

1. Parham, D. M., Roloson, G. J., Feely, M., Green, D. M., Bridge,J. A. and Beckwith, J. B.: Primary malignant neuroepithelialtumors of the kidney: a clinicopathologic analysis of 146 adultand pediatric cases from the National Wilm’s Tumor StudyGroup Pathology Center. Am J Surg Pathol, 25: 133, 2001

2. Paulussen, M., Frohlich, B. and Jurgens, H.: Ewing tumour:incidence, prognosis and treatment options. Paediatr Drugs, 3:899, 2001

3. Gousse, A. E., Roth, D. R., Popek, E. J., Cooley, L. D. andHorowitz, M. E.: Primary Ewing’s sarcoma of the bladderassociated with an elevated antinuclear antibody titer. J Urol,158: 2265, 1997

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