NEOPLASTIC TRANSFORMATION OF UNDESCENDED TESTIS SEEN ON FDG PET/CT

Abstract

We present the case of a 60-year-old male presented with biopsy proven metastatic right pelvic mass of unknown primary. No abnormality other than right pelvic mass was present in recent CT with limited sections. He was referred for FDG PET/CT to look for primary neoplastic focus and further staging. The FDG PET/CT was performed with 112 MBq of ¹⁸FDG after 60-minute skull to mid-thigh images were acquired using a low-dose, non-contrast enhanced CT protocol. There was redemonstration of large heterogenous necrotic right pelvic mass with non-homogenous FDG distribution pushing bladder to left. The mass was measuring 109 x 98 x 106 mm in Transverse (TS) x Antero posterior (AP) x Cranio caudal (CC) dimensions with SUVmax 12.5 (Ref red arrow of all sections of Figure 1). Right testis was not seen in scrotal sac. Left testis was seen in scrotal position without abnormal FDG uptake. A non-FDG avid well defined necrotic node was seen in aortocaval region at L2 level, measuring 16 x 12 x 26 mm (TS x AP x CC) not covered in recent pelvic CT (ref green arrow of section E-F of Figure 1). No evidence of hypermetabolic nodal, pulmonary, hepatic, splenic, adrenal or bony metastasis was seen in rest of scan. Based on the scan findings, the case was reported as likely neoplastic transformation of undescended right testis. On follow up, all three testicular markers (1) Alfa fetoprotein (AFP), (2) beta Human chorionic gonadotropin (βHCG) and (3) Lactate dehydrogenase (LDH) were elevated and favored initial diagnosis.