Indian Journal of Pathology and Microbiology

: 2012  |  Volume : 55  |  Issue : 4  |  Page : 569--571

Cytokeratin-positive primitive neuroectodermal tumor of the prostate: Case report and review of literature

Ibrahim Al Haddabi1, Maiya Al Bahri1, Ikram Burney2,  
1 Department of Pathology, College of Medicine, Sultan Qaboos University, Sultanate of Oman
2 Department of Medicine, Medical Oncology Unit, Sultan Qaboos University, Sultanate of Oman

Correspondence Address:
Ibrahim Al Haddabi
Sultan Qaboos University. P. O. Box 2572, PC 111 Muscat
Sultanate of Oman


Ewing«SQ»s sarcoma/primitive neuroectodermal tumor (ES/PNET) of the prostate is extremely rare. Here, we report a case of ES/PNET of prostate in a 24-year-old man presenting with dysuria and pelvic discomfort. Computed tomography scan revealed a heterogeneous mass involving the prostate without evidence of distant metastases. Histologically, the tumor was composed of small round blue cells strongly and diffusely positive for CD99 and epithelial markers. Fluorescence in situ hybridization confirmed rearrangement of the Ewing«SQ»s sarcoma region on chromosome 22.

How to cite this article:
Al Haddabi I, Al Bahri M, Burney I. Cytokeratin-positive primitive neuroectodermal tumor of the prostate: Case report and review of literature.Indian J Pathol Microbiol 2012;55:569-571

How to cite this URL:
Al Haddabi I, Al Bahri M, Burney I. Cytokeratin-positive primitive neuroectodermal tumor of the prostate: Case report and review of literature. Indian J Pathol Microbiol [serial online] 2012 [cited 2020 Oct 22 ];55:569-571
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Ewing's sarcoma/primitive neuroectodermal tumors (ES/PNETs) are rare tumors and account for 1% of all sarcomas. ES/PNETs commonly involve soft tissues or bone of children and young adults. Primary cases have been reported in visceral sites such as parotid gland, lung, kidney, urinary bladder, uterus, pancreas, and testis. Only six cases arising from the prostate have been reported. [1],[2],[3],[4],[5],[6] Here, we present the seventh case.

 Materials and Methods

The patient was admitted at our institution and the clinical information was obtained from the hospital computer data base. The biopsy tissues were fixed in 10% formalin. Paraffin-embedded tissue sections were prepared at 5 μm thickness. The sections were stained with hematoxylin and eosin.

Immunohistochemistry was performed using Envision-dual link HRP. The antibodies used were CD99, LCA, TdT, desmin, vimentin, cytokeratin AE1/AE3, pankeratin, CK19, HMW CK, myo-D1, PSA, synaptophysin, chromogranin, NSE, EMA, and TTF1. Four-micrometer thick paraffin-embedded sections were prepared for FISH analysis using the LSI (R) EWSR1 (22q12) dual color, break apart re-arrangement probe.


Clinical Features

A 24-year-old man presented with a 2-year history of dysuria, constipation, low back pain, pelvic discomfort, and weight loss. General physical examination was unremarkable. Digital rectal examination revealed a firm mass felt involving the prostate, the superior margin of which could not be reached.

Biochemical investigations were within the normal range. The serum PSA level was 0.7 ng/ml. Abdominal and pelvic computed tomography scan showed a large heterogeneous mass within the pelvis measuring 10 × 9 × 6 cm [Figure 1]. The mass originated below the bladder neck and displaced the bladder anteriorly. The prostate gland was replaced by the mass.{Figure 1}

Pathologic Findings

The biopsy sample consisted of four cores of prostatic tissue, the largest measuring 1.6 cm in length and the smallest 0.6 cm in length. Histological examination showed a neoplasm composed of sheets of small round cells with round, hyperchromatic nuclei, and small nucleoli [Figure 2]a. The cytoplasm was scanty with indistinct cell membranes. Apoptotic and mitotic figures were present and there were a few foci of necrosis. True rosettes and pseudovascular pseudo-rosettes were not seen. Benign prostatic glands were seen focally.{Figure 2}

Immunohistochemical and Molecular Tests

Immunohistochemical stains showed the neoplastic cells to be strongly and diffusely positive for CD99, Bcl2, CK19, and AE1/AE3 [Figure 2]b-d. The majority of the cells were also positive for pan-cytokeratin (CK) and vimentin. The cells were negative for LCA, TdT, S100, myo-D1, myoglobin, desmin, chromogranin, CD56, PSA, WT1, NSE, TTF1, synaptophysin, and HMWCK.

A molecular analysis is important to reach the accurate diagnosis. In our case, FISH analysis revealed rearrangement of the EWSR1 gene region on chromosome 22q12 using the LSI (R) EWSR1 (22q12) dual color, break apart re-arrangement probe. The t (X, 18) for synovial sarcoma was negative.


The histological differential diagnosis included small cell carcinoma of prostate, lymphoblastic lymphoma, rhabdomyosarcoma, desmoplastic small round cell tumor, and primitive neuroectodermal tumor. The immunohistochemical stains are helpful in the diagnosis. Small cell carcinoma of the prostate was ruled out because of negativity for chromogranin, synaptophysin, PSA, and CD56 and positivity for CD99. In addition, the age of the patient was not consistent with this diagnosis. Lymphoblastic lymphoma, rhabdomyosarcoma, and desmoplastic small round cell tumor were ruled out by the negativity for LCA, TdT, desmin, WT1, and myo-D1.

Prostatic sarcoma is an extremely rare tumor. It accounts for less than 0.1% of primary prostate cancer types in adults, occurring in relatively younger men aged between 35 and 60. [7]

ES/PNET of the prostate is an extremely rare tumor, with only six reported cases in the literature [Table 1]. Age of initial presentation ranged from 20 to 31. As in our case, almost all cases presented with dysuria and found to have a pelvic mass on digital rectal examination. The imaging studies in all cases revealed a heterogeneous large mass ranging from 6.7 to 10 cm. The PSA level ranged from 0.3 to 2.06 ng/ml. Pulmonary metastasis was reported in one case only; the other cases including ours were negative for distant metastasis. All the reported cases were positive for CD99 and negative for cytokeratin stains. Our case was positive for both CD99 and cytokeratin.{Table 1}

CD99 is not specific for EWS/PNET. [8] This marker has been reported in other tumors including lymphoblastic lymphoma, alveolar rhabdomyosarcoma, granulocytic sarcoma, and synovial sarcoma. Cytokeratin expression is present in about 20% of EWS/PNET in either diffuse or focal pattern. [9],[10] The positivity for pan-CK, AE1/AE3, and BCl2 raise the possibility of poorly differentiated synovial sarcoma. It was found that 60-70% of synovial sarcomas stain for CK7 and CK19, but rarely expressed in ES/PNET.

Ninety percent of ES/PNET are characterized by the translocation t (11, 22) (q24, q12) which results in ES/FLI1 fusion protein. The translocation can be demonstrated by molecular techniques such as reverse transcriptase-polymerase chain reaction (RT-PCR) and/or FISH analysis. No significant differences in specificity or sensitivity have been reported between FISH and RT-PCR. The present case emphasized the usefulness of FISH in the diagnosis especially in cytokeratin-positive cases.

The prognosis for patients with ES/PNET has improved with the current management. Our patient was treated with combination chemotherapy consisting of Ifosfamide, doxorubicin, vincristine, and etoposide. The patient is alive without evidence of distant metastasis.

In summary, we report a rare case of cytokeratin-positive ES/PNET arising from the prostate. This tumor should be differentiated from other small blue cell tumors using the appropriate immunohistochemical stains. In difficult cases, molecular studies are the gold standard for an accurate diagnosis.


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