Extrahepatic metastases of hepatocellular carcinoma on 18F FDG PET CT

Background To determine locations, relative frequencies, imaging features, and pattern of distribution of extrahepatic metastasis from hepatocellular carcinoma (HCC) on 2-deoxy-2-[fluorine-18]fluoro-D-glucose (18F-FDG) PET CT. Methods FDG PET CT scans of 224 consecutive patients of HCC acquired between 2010 and 2018 were reviewed. Fifty-six patients detected with extrahepatic metastasis on FDG PET CT were retrospectively analyzed. Findings were correlated with prior/follow-up imaging studies, clinical findings, FNAC, or biopsy findings whenever available. Descriptive analysis of location, relative frequencies, imaging features, and pattern of distribution of extrahepatic metastasis was done. Results Commonest were metastatic pulmonary nodules (55.3% patients), most of them being well-defined solid lesions (53.5%) with bilateral involvement in 44.6% patients and lower lobes of lungs along with other lobes being more frequently involved (41.0% patients). While in 7.14% patients lung nodules were FDG avid, 23.2% patients had both FDG avid and non-avid pulmonary nodules. Second most common were regional metastatic lymph nodes in 44.65% of patients seen at aortocaval (25%), paraaortic (23.21%), portocaval (21.4%), and left gastric nodal (17.8% of patients) stations. Twenty-five percent of patients had FDG avid lymph nodes and 5.36% patients had both FDG avid and FDG non-avid lymph nodes. Distant metastatic lymph nodes were third most common in 39.2% of patients seen at paratracheal (2.5%), juxtaphrenic (8.9%), and mesenteric lymphnodal (7.1%) stations. Twenty-five percent of patients had FDG avid lymph nodes while 5.36% patients had both FDG avid and FDG non-avid lymph nodes. Skeletal involvement was seen in 32.1% of patients. Commonest sites are vertebrae (16.7%), pelvis (14.2%), and ribs (10.7% patients). Six out of 7 patients had unilateral adrenal gland involvement. Bilateral adrenal gland involvement was seen in 1 patient. FDG non-avid peritoneal/omental metastases was seen in 2 patients. Brain, spleen, and muscle metastatic lesions were seen in 1 patient each out of 56 patients (1.79%). Conclusions Lungs, regional and distant lymph nodes and skeleton are the most frequently involved sites of extrahepatic metastatic hepatocellular carcinoma. Adrenal glands, muscles, brain and peritoneum are also involved but to a lesser extent.