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Annals of Oncology 12: 1485-1488. 2001. © 2001 Kluwer Academic Publishers. Printed in the Netherlands.

Clinical case
PET and PLAP in suspected testicular cancer relapse: Beware sarcoidosis
C S. Karapetis,1 A. H. Strickland,1 D. Yip,1 J. D. van der Walt2 & P. G. Harper1
Departments of * Medical Oncology. Guy's Hospital. London. 2 Histoputhology, St Thomas' Hospital. London. UK

Summary A31-year-old man previously treated with chemotherapy for metastatic testicular cancer presented with new mediastinal lymphadenopathy and peripheral lung opacities. Serum tumour markers were not elevated and a PET (positron emission tomography) scan revealed increased FDG (fluoro-deoxyglucose) uptake in the lungs and mediastinum consistent with testis cancer relapse. A biopsy of a mediastinal lymphnode was performed and the pathology was that of sarcoidosis. Immunohistochemistry however was positive for PLAP (placental alkaline phosphatase) and negative for EMA (epithelial membrane antigen). This immunohistochemical profile raised

concerns that the observed pathology represented a sarcoid reaction to micro-metastatic testicular cancer relapse. We performed immunohistochemical pathologyanalysis on four known cases of sarcoidosis and found the same immunohistochemical-staining pattern. This case highlights the problem of specificity when interpreting the significance of PET scans and immunohistochemical analysis in this situation. Sarcoidosis, a condition that has been associated with testicular cancer, should always be considered in the differential diagnosis.

Key words:alkaline phosphatase, immunohistochemistry, sarcoidosis, testicular neoplasm, tomography

Introduction Testicular cancer is a relatively uncommon malignancy, accounting for 1% of diagnosed cancers [1]. It is, however, the most common cancer diagnosed in men aged 15-35 years, and the incidence is rising [2]. Patients are usually monitored following primary therapy with regular medical examination,serum tumour marker measurement, and radiological imaging. The imaging modality of positron emission tomography (PET) has a potential role in the initial staging and follow-up of these patients. Histological examination is the cornerstone of establishing a definite and accurate diagnosis of testis cancer relapse. Immunohistochemical staining with markers such as oc-fetoprotein (AFP), (3-humanchorionic gonadotrophin (HCG) and human placental alkaline phosphatase (hPLAP) can be a useful adjunct in pathological evaluation of germ cell tumour specimens. In this report we describe a case of suspected testicular cancer relapse as suggested by PET scan and immunohistochemistry findings. We highlight the association of sarcoidosis and testicular cancer and comment on the potential impact of thisassociation on the interpretation of the radiological and pathological findings in suspected cancer relapse.

revealed embryonal carcinoma with vascular invasion in the right testis and seminoma involving the left testis. Pre-operative lactate dehydrogenase (LDH) and AFP were normal but HCG was elevated at 27 IU (Normal < 5). This fell to within normal limits following the orchidectomy. Serum hPLAPwas not measured. CT scan showed no evidence of metastatic disease and the patient did not receive adjuvant therapy. Five months later a CT scan revealed two round right lung lesions measuring 2 cm and 1.8 cm in diameter. Serum tumour markers (AFP, HCG, LDH) were not elevated. He was treated with BEP chemotherapy (bleomycin 30 mg intravenously (i.v.) days 2, 8, 15, etoposide 100 mg/m 2 i.v. day1-5, cisplatin 20 mg/m" i.v. day 1-5 with cycles repeated at three weekly intervals). Repeat imaging by CT scan after three cycles of chemotherapy confirmed a radiological complete response. A follow-up CT scan performed two years later revealed new bilateral pleural based lung opacities and mediastinal lymphadenopathy with a maximum diameter of 4 cm. He was asymptomatic and serum tumour markers...