Lobo, João

Abstract Objectives Fibronodular hepatocellular carcinoma (FN-HCC) is a newly described variant of hepatocellular carcinoma (HCC), with only 29 cases reported. Histologically, it is divided into multiple smaller, well-defined tumor nodules by extensive fibrosis. Its differential diagnosis includes other HCC variants characterized by fibrous stroma, such as fibrolamellar hepatocellular carcinoma and scirrhous hepatocellular carcinoma. Fibronodular hyperplasia may also be considered in the differential diagnosis. We are reporting 7 cases to help better understand this entity. Methods We retrospectively identified 7 cases of FN-HCC and analyzed the clinical and histologic features of each tumor, as well as disease progression and patient prognosis. Results The FN-HCC cases were diagnosed at a median age of 58 years (range, 40-75 years), with a male predilection (n = 6, 86%). Most patients were White (n = 6, 86%), and 1 was African American (n = 1, 14%). Tumors had a mean size of 3.15 cm (range, 1-9 cm) and were mainly located in the right lobe (n = 5, 71%). Background liver was cirrhotic in 6 cases (86%). Five patients were hepatitis C positive (71%). All tumors were surgically removed, with a free resection margin. Among 3 patients with evident vascular invasion, 1 had a positive lymph node. This patient had tumor metastasis 6 years later; otherwise, all patients were disease free on follow-up. Conclusions Our cohort was concordant with published data showing a male predilection, hepatitis C association, and good prognosis when the disease is discovered before metastasis and is surgically excised with negative margins. However, it contradicts the published literature that associates FN-HCC with the absence of advanced fibrosis/cirrhosis.

Juxtaglomerular cell tumor (JxGCT) is a rare type of renal neoplasm demonstrating morphologic overlap with some mesenchymal tumors such as glomus tumor (GT) and solitary fibrous tumor (SFT). Its oncogenic drivers remain elusive, and only a few cases have been analyzed with modern molecular techniques. In prior studies, loss of chromosomes 9 and 11 appeared to be recurrent. Recently, whole-genome analysis identified alterations involving genes of MAPK-RAS pathway in a subset, but no major pathogenic alterations have been discovered in prior whole transcriptome analyses. Considering the limited understanding of the molecular features of JxGCTs, we sought to assess a collaborative series with a multiomic approach to further define the molecular characteristics of this entity. Fifteen tumors morphologically compatible with JxGCTs were evaluated using immunohistochemistry for renin, single-nucleotide polymorphism array (SNP), low-pass whole-genome sequencing, and RNA sequencing (fusion assay). In addition, methylation analysis comparing JxGCT, GT, and SFT was performed. All cases tested with renin (n=11) showed positive staining. Multiple chromosomal abnormalities were identified in all cases analyzed (n=8), with gains of chromosomes 1p, 10, 17, and 19 and losses of chromosomes 9, 11, and 21 being recurrent. A pathogenic HRAS mutation was identified in one case as part of the SNP array analysis. Thirteen tumors were analyzed by RNA sequencing, with 2 revealing in-frame gene fusions: TFG::GPR128 (interpreted as stochastic) and NAB2::STAT6. The latter, originally diagnosed as JxGCT, was reclassified as SFT and excluded from the series. No fusions were detected in the remaining 11 cases; of note, no case harbored NOTCH fusions previously described in GT. Genomic methylation analysis showed that JxGCT, GT, and SFT form separate clusters, confirming that JxGCT represents a distinct entity (ie, different from GT). The results of our study show that JxGCTs are a distinct tumor type with a recurrent pattern of chromosomal imbalances that may play a role in oncogenesis, with MAPK-RAS pathway activation being likely a driver in a relatively small subset.