Ultrasound (US) LI-RADS: Outcomes of Category US-3 Observations.

OBJECTIVE. The purpose of the study is to evaluate the outcomes of ultrasound (US) LI-RADS category US-3 observations detected at US performed for hepatocellular carcinoma (HCC) screening and surveillance on the basis of subsequently performed multi-phase MRI or CT or histopathology. MATERIALS AND METHODS. In this retrospective analysis, 267 patients at high risk for HCC (161 men and 106 women; mean [± SD] age, 58.6 ± 12.2 years) underwent screening liver US between January 2017 and June 2019 and were assigned US-3 observations on a prospective clinical basis using the US LI-RADS algorithm. The results of follow-up imaging studies and/or histopathology were analyzed. RESULTS. Visualization scores assigned at US were A (40.8% [109/267]), B (52.8% [141/267]), and C (6.4% [17/267]). Reasons for US-3 observations included a measurable mass of 1 cm or larger (88.8% [237/267]; mean size, 1.8 ± 1.0 cm; range, 1.0-6.9 cm), an area of parenchymal distortion of 1 cm or greater (7.9% [21/267]; mean size, 1.8 ± 0.9 cm; range, 1.0-4.0 cm), or a new venous thrombus (3.4% [9/267]). Confirmatory testing with multiphase contrast-enhanced MRI or CT or with histopathology was available for 81.6% (218/267) of patients. Causes of US-3 observations included no abnormality at MRI or CT (41.3% [90/218]), a benign lesion (32.6% [71/218]), a LI-RADS category 3 (LR-3) observation at MRI or CT (5.5% [12/218]), a LI-RADS category 4 or 5 (LR-4 or LR-5) observation at MRI or CT or identification of HCC at histopathology (18.8% [41/218]), and an LR-M (denoting probably or definitely malignant but without specific features for HCC) observation at MRI or CT or other malignancy at histopathology (1.8% [4/218]). The PPV of a US-3 observation for probable or definite HCC was 18.8%, and for any malignancy it was 20.6%. CONCLUSION. In the HCC screening population, approximately one in five US-3 observations represents probable or definite HCC at multiphase MRI or CT or HCC at histopathology. These findings support current US LI-RADS guidelines to pursue further evaluation with multiphase cross-sectional imaging for US-3 observations.

Identification and characterization of a welwitindolinone alkaloid biosynthetic gene cluster in the stigonematalean Cyanobacterium Hapalosiphon welwitschii.

The identification of a 36 kb welwitindolinone (wel) biosynthetic gene cluster in Hapalosiphon welwitschii UTEX B1830 is reported. Characterization of the enzymes responsible for assembling the early biosynthetic intermediates geranyl pyrophosphate and 3-((Z)-2'-isocyanoethenyl)indole as well as a dedicated N-methyltransferase in the maturation of N-methylwelwitindolinone C isothiocyanate solidified the link between the wel pathway and welwitindolinone biosynthesis. Comparative analysis of the ambiguine and welwitindolinone biosynthetic pathways in two different organisms provided insights into the origins of diverse structures within hapalindole-type molecules.