Rare initial presentation of prostate cancer

Authors: Chan, NHL; Toh, CK
Corresponding Author: Chay, W

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WY Chay 1, NHL Chan 2, CK Toh 1
1 Department of Medical Oncology, National Cancer Centre Singapore 2 Department of Pathology, Singapore General Hospital
Correspondence: WY Chay, Department of Medical Oncology, National Cancer Centre Singapore, 11 Hospital Drive, Singapore 169610. Tel: (65) 64368000, Fax: (65) 62256283, Chay.W.Y@nccs.com.sg
Peritoneal metastasis arising from prostate cancer is a very rare phenomenon. We present a rare case of a patient presenting with ascites and carcinomatosis peritoneii from a prostate primary. Our patient presented with progressive abdominal distension, slow stream of urine and weight loss. Physical examination revealed abdominal distension, but no hepatosplenomegaly or lymphadenopathy. In addition, a mildly enlarged prostate was felt on digital rectal examination. CT scan of the abdomen and pelvis showed gross ascites with omental caking and enhancing peritoneal nodules. No obvious primary was seen. An incidental finding of synchronous pharyngeal squamous cell carcinoma was found on OGD. Peritoneal fluid cytology was unremarkable. Serum PSA was 902 ug/dL. Laparoscopy and biopsy of peritoneal nodules enabled a histological confirmation of poorly differentiated prostatic adenocarcinoma which was PSA-negative but PSMA-, prostatic acid phosphatise- and AMACR-positive. Bone scan did not show any evidence of bone metastases. He was subsequently started on complete androgen blockage with zoladex and casodex for treatment of his prostate cancer and radiotherapy to his pharyngeal cancer. This case report is important in that it is generally not widely recognized that prostate cancer metastasizes to the peritoneum. In the literature, peritoneal metastasis from prostate cancer, if present, are usually associated with other sites of metastases and found at very advanced stages of the disease. In our patient carcinomatosis peritonei was the first presentation which led to the diagnosis of prostate cancer and was the only site of metastasis.
Case report A 78 year old Chinese man presented with progressive abdominal distension over 3 months. Physical examination revealed a distended abdomen with ascites and no organomegaly. Digital rectal examination revealed a smooth, mildly enlarged prostate. The only abnormality on serum tumor markers analysis was an elevated level of prostate specific antigen (PSA) of 902 ng/mL. Chest radiograph was unremarkable. Computed tomography scan of the thorax and abdomen showed gross ascites with omental caking and enhancing peritoneal nodules (Figure 1). Oesphagoduodenoscopy was done to exclude an upper gastrointestinal tract primary tumor, but instead found a pharyngeal mass for which biopsy showed a moderately differentiated squamous cell carcinoma. CT scan of the neck was then performed which showed a pharyngeal mass with cervical lymphadenopathy. Bone scan was negative for bone metastases. As it is very rare for squamous cell carcinoma of the pharynx to metastasise to the peritoneum, abdominal paracentesis was performed twice to identify the cause of the ascites. On both occasions, the peritoneal fluid was exudative and only revealed lymphocytes with no malignant cells. A diagnostic laparoscopy and biopsy of his peritoneal nodules was performed. The histology showed features of poorly differentiated adenocarcinoma (Figure 2); CK7 negative, CK20 positive, PSA negative but PSMA (Prostatic Specific Membrane Antigen), PSAP ( Prostatic Acid Phosphatase), AMACR (Alpha-methylacyl-CoA racemase) positive, consistent with a prostatic primary. (Figure 3). He was started on complete androgen blockage with Bicalutamide (Casodex TM) 50 mg OM and Goserelin 10.8 mg 3 monthly (Zoladex TM) initially but Bicalutamide was stopped after 2 months when the ascites resolved. He is presently on 3-month goserelin injection with no recurrence of the ascites and a recent PSA reading of 2.6 ng/mL. He was also given a course of external beam palliative radiotherapy to the pharyngeal squamous cell carcinoma.
Discussion Carcinomatosis peritoneii frequently presents with symptomatic abdominal distension and ascites, with 70% of peritoneal metastasis found to be adenocarcinoma at diagnosis. Causes of peritoneal metastasis frequently arise secondary to primary malignancies from the gastrointestinal tract (such as the colon, stomach) or gynaecological malignancies such as ovarian carcinoma.
Prostate cancer frequently metastasizes to the skeleton, lymph nodes and other sites.1 To our knowledge, there is only one case report that reported peritoneal metastasis from prostate cancer2. In that report, the patient was previously diagnosed with prostate cancer four years prior to his peritoneal metastasis. In contrast, for our patient, carcinomatosis peritonei was the only metastatic site and was the first presentation of his prostate cancer. In our patient, the adenocarcinoma did not stain positive for PSA. It is known that the intensity of PSA immunostaining correlates with the grade of malignancy with decrease in staining for poorly differentiated high grade tumor3 However, the presence of AMACR (Alpha-methylacyl-CoA racemase), prostatic acid phosphatase (PAP) and PMSA (Prostatic Specific Membrane Antigen), confirmed the primary as from the prostate.4 Other possible explanations would include the presence of focal neuroendocrine differentiation in the background of ductal adenocarcinoma of the prostate in our patient. Unfortunately, we did not have any transurethral resection of prostate (TURP) chips to have a better understanding of the histology in our patient, as he declined TURP. Further studies would be helpful to elucidate the relationship between PSA positivity and the histological subtype of various prostate carcinomas. In addition, studies into patients who present with low levels of serum PSA have determined that PAP can be present in up to 70% despite low serum PSA levels and may be of use in the diagnosis of PSA negative prostate cancers 4. Other markers of value in the diagnosis of prostate cancer in patients who present with a high clinical suspicion of the disease but have low serum PSA levels include use of PMSA and Androgen receptor (AR) levels.
Further proof that the ascites is due to prostatic primary is the improvement after androgen deprivation therapy. A number of case reports have also shown benefit if the use of primary or secondary hormonal manipulations in patients with prostate cancer with metastasis to pleural lining. Go et al. reported a single case of a massive pleural effusion secondary to prostate cancer which resolved completely following secondary hormonal manipulation using dexamethasone in a patient with hormone refractory metastatic prostate cancer5.
We would like to illustrate, with our case report, that prostate cancer can be a rare cause for peritoneal metastasis. In the case of an unknown primary carcinomatosis peritoneii in a male patient, a simple blood test for PSA to exclude a prostatic primary is advisable. In patients with massive ascites or effusions secondary to a prostate malignancy, the use of primary or secondary hormonal manipulations would aid with palliation and symptom control.
Figure 1: CT scans showing peritoneal nodules and omental caking
Figure 2: Poorly differentiated adenocarcinoma from histology of peritoneal nodule. (Main picture magnification of 40x, Magnification of inset 80x)
Figure 3: Positive immunostaining of specimen from peritoneal nodules for presence of AMACR (Alpha-methylacyl-CoA racemase), prostatic acid phosphatase (PAP) and PMSA (Prostatic Specific Membrane Antigen) which are all prostate markers. (Magnification of main picture is 40x, magnification of inset 80x).
1) Mohile SG, Lachs M, Dale W. Management of prostate cancer in the older man. Semin Oncol. 2008 Dec;35(6):597-617
2) EO Kehinde, Aberdeen SM, A. Al-Hunayan et al. Prostate cancer metastatic to the omentum. Scand J Urol Nephrol 36: 225-227, 2002 p 225-227
3) M Aihara, RM Lebovitz, TM Wheeler et al. Prostate specific antigen and gleason grade: an immunohistochemical study of prostate cancer. J Urol 1994; 151: 1558-64
4) AJ Birtle, A Freeman, JRW Masters et al. Tumour markers for managing men who present with metastatic prostate cancer and serum prostate-specific antigen levels of <10ng/ml. BJU 2005; 96,p303-307
5) Go RS, Klee GG, Richardson RL. Use of pleural fluid prostate specific antigen in the diagnosis of malignant pleural effusion from metastatic prostate cancer. J urol 2000;164:459

Date added to bjui.org: 13/10/2009 (publication information)
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CASE REPORTS: Carcinomatosis peritonei as first presentation of carcinoma of the prostate

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