A 54-year-old female underwent tru-cut biopsy from mass lesions detected on USG at liver and histopathology revealed metastasis of adenocarcinoma. A ¹⁸F-FDG PET/CT scan was performed to evaluate the extent of the disease and determine the primary site of malignancy.

Hypermetabolic lesions at liver representing metastases from primary malignant lesion at sigmoid colon.

Adenocarcinoma is the most commonly encountered histology among patients with CUP. Most patients have a small primary tumor that can metastasize, and the metastases grow while the primary tumor usually remains small.

A 71-year-old male who was being followed up with the diagnosis of lung cancer underwent ¹⁸F-FDG PET/CT for restaging.

Hypermetabolic lesions at right lung are compatible with primary lung cancer and there is also a metastatically involved right supraclavicular lymph node. Focal hypermetabolic lesion at prostate gland is suspicious for malignancy.

Biopsy from the lesion at prostate gland revealed adenocarcinoma.

Although prostate adenocarcinomas show generally no or mild FDG uptake, poorly differentiated cancers or those with a rapid cell turnover may exhibit increased FDG uptake and show FDG-avid areas within the prostate. Since the benign lesions can also show FDG uptake, it is not always easy to decide whether a hypermetabolic lesion at prostate gland is benign or not.