Please cite this article in press as: Sharma P, et al. Mediastinal germ cell tumor presenting with bone marrow metastases: An unusual pat- tern of relapse demonstrated with 18 F-FDG PET–CT. Rev Esp Med Nucl Imagen Mol. 2013. http://dx.doi.org/10.1016/j.remn.2013.07.004 ARTICLE IN PRESS G Model REMNIM-524; No. of Pages 2 Rev Esp Med Nucl Imagen Mol. 2013;xxx(xx):xxx–xxx Interesting image Mediastinal germ cell tumor presenting with bone marrow metastases: An unusual pattern of relapse demonstrated with 18 F-FDG PET–CT Tumor de células germinales en mediastino con metástasis en médula ósea: un patrón inusual en recaída demostrado con 18 F-FDG PET/TAC P. Sharma, S.K.C. Sudhir, V.S. Dhull, T.K. Jain, C. Bal, R. Kumar * Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India a r t i c l e i n f o Article history: Received 26 June 2013 Accepted 26 July 2013 Available online xxx A 25-year-old male presented with an anterior mediasti- nal mass. Based on elevated serum alpha-fetoprotein, computed tomography findings and cytology, a diagnosis of primary medi- astinal germ cell tumor was made. He underwent neoadjuvant chemotherapy followed by surgical removal of the anterior medi- astinal mass. Post operative histopathology revealed the mass to be a nonseminomatous germ cell tumor. At 6 month follow up the serum alpha-fetoprotein levels were elevated (71.04 ng/ml; nor- mal range: 1–8). Contrast enhanced CT of chest and abdomen were normal. Because of persistently elevated serum alpha-fetoprotein levels the patient underwent 18 F-fluorodeoxyglucose ( 18 F-FDG) positron emission tomography–computed tomography (PET–CT) to localize the site of recurrence. PET–CT (Fig. 1) revealed multiple focal areas of intense 18 F-FDG uptake at multiple skeletal sites with no corresponding CT abnormalities (A–F), including facial bones (B, C, arrow). As contrary to diffuse bone marrow 18 F-FDG uptake seen post chemotherapy, the 18 F-FDG uptake seen in this case was patchy (E, F, arrow). Therefore a diagnosis of extensive bone marrow metastasis was made on 18 F-FDG PET–CT. As bone or bone marrow metastasis is extremely rare in germ cell tumors, the patient under- went bone marrow biopsy of sacrum based on PET–CT findings which confirmed the diagnosis of metastatic deposits from germ cell tumor. The patient is being planned for second line chemother- apy. Primary mediastinal germ cell tumor is a rare subgroup of germ cell tumors accounting for less than 5% of all germ cell malignancies. 1 It is more common in men than in women. In addi- tion, it displays different biological behavior in men as compared to testicular germ cell tumors. Histologically, it can be classically * Corresponding author. E-mail address: rkphulia@yahoo.com (R. Kumar). divided into three categories: seminomas, nonseminomatous and mixed. Cisplatin based chemotherapy regimens followed by sur- gical consolidation results in long-term progression-free survival and overall survival time, which is recommended as the first- line therapy. Patients with pure seminomatous histology in the mediastinum are reported to have chances of long-term cure of almost 90%, but only 45% of patients with mediastinal nonsemi- nomas are estimated to be alive at 5 years. 1 The common sites of metastasis include lung, nodes, brain and liver. Bone marrow is an extremely rare site of metastasis with only few reported cases in literature. 2 It can be difficult to detect with CT, MRI or bone scan and will require bone marrow biopsy. 2 As bone marrow biopsy is not routinely done for such tumors, making a diagnosis can be extremely difficult if there are no hematological abnormalities. 18 F-FDG PET–CT has been shown to be useful for detecting bone marrow lesions in patients with various underlying disorders, but not germ cell tumors. 3 By demonstrating such rare site of relapse it changed the management in this patient. However, other rare causes of false positive bone marrow 18 F-FDG uptake on PET–CT like prior chemotherapy, colony stimulating factor therapy, sarcoido- sis and infections which could mimic metastases should be kept in mind. 18 F-FDG PET–CT has been shown to be useful in patients with mediastinal germ cell tumor. It is useful for demonstration of distant metastasis, monitoring response to treatment, for assess- ment of residual masses after therapy as well as for prognosis of these patients. The present case further highlights its utility in such tumors by demonstrating unusual sites of relapse. At relapse, earlier administration of second-line chemotherapy can improve survival and quality of life, making the detection of relapse crucial. 2253-654X/$ – see front matter © 2013 Elsevier España, S.L. and SEMNIM. All rights reserved. http://dx.doi.org/10.1016/j.remn.2013.07.004