Histogenetic insights and genetic landscape of fibromatosis-like undifferentiated gastric carcinoma: a focused study.

BACKGROUND: The aim of this study was to elucidate the histogenesis and genetic underpinnings of fibromatosis-like undifferentiated gastric carcinoma (FLUGC), a rare pathological entity. METHOD: Through a detailed analysis of seven cases, including histopathological evaluation, CTNNB1 gene mutation screening, human epidermal growth factor receptor 2 (HER2) protein level quantification, and HER2 gene amplification assessment to identify the pathological and molecular characteristics of FLUGC. RESULTS: Of the seven patients in this study, five were male and two were female (age: 39-73 years). Four patients presented with lesions in the gastric antrum and three had lesions in the lateral curvature of the stomach. Histopathologically, over 90% of the tumor consisted of aggressive fibromatosis-like tissue, including proliferating spindle fibroblasts and myofibroblasts and varying amounts of collagenous fibrous tissues. Undifferentiated cancer cells, accounting for less than 10%, were dispersed among the aggressive fibromatosis-like tissues. These cells were characterized by their small size and were relatively sparse without glandular ducts or nested mass-like structures. Immunophenotyping results showed positive expression of CKpan, CDX2, villin, and p53 in undifferentiated cancer cells; positive expression of vimentin in aggressive fibromatosis-like tissue; positive cytoplasmic expression of ß-catenin; and focal cytoplasmic positive expression of smooth muscle actin (SMA). Genetic analysis did not reveal any mutations in the CTNNB1 gene test, nor was there amplification in the HER2 gene fluorescence in situ hybridization (FISH) test. Additionally, the Epstein-Barr encoding region (EBER) of in situ hybridization was negative; and the mismatch repair (MMR) protein was positive. Programmed cell death-1 (PD-1) was < 1-5%; programmed cell death ligand 1 (PD-L1): TPS = 1-4%, CPS = 3-8. CONCLUSION: The study highlights the significance of CTNNB1, HER2, EBER, and MMR as pivotal genetic markers in FLUGC, underscoring their relevance for diagnosis and clinical management. The rarity and distinct pathological features of FLUGC emphasize the importance of accurate diagnosis to prevent underdiagnosis or misdiagnosis and to raise awareness within the medical community.

Assessing clinical pathological characteristics and gene expression patterns associated with hepatoid adenocarcinoma of the stomach.

OBJECTIVE: The objective of this study is to assess the clinical pathological attributes of Hepatoid Adenocarcinoma of the Stomach (HAS) and to delineate the differential diagnostic considerations about it. METHOD: The investigation involved analyzing 31 HAS cases using histomorphological assessment, immunohistochemical profiling, and relevant gene detection methodologies. RESULTS: Among the 31 HAS cases, 9 (29.0%) were of trabecular hepatoid adenocarcinoma of the stomach, 7 (22.6%) were of glandular hepatoid adenocarcinoma of the stomach, 4 (12.9%) were of nesting hepatoid adenocarcinoma of the stomach, 3 (9.7%) were of clear cell hepatoid adenocarcinoma of the stomach, and 8 (25.8%) were of diverse hepatoid adenocarcinoma of the stomach. Of these 31 cases, 24 were male, accounting for 77.4% of the cases. Serum alpha-fetoprotein (AFP) levels were notably elevated, with radioimmunoassay results reaching 1240 ng/ml; 28 out of 31 cases had AFP levels below 25 µg/l, accounting for 90.3%. Related genes: HER2 protein indicated positive expression on the cell membrane in 35.5% (11/31) of the cases; HER2 gene amplification detected by the FISH technique was 12.9% (4/31). Tumoral stromal lymphocytes exhibited a PD-1 positive expression rate of 58.1% (18/31). In gastric cancer tissues, the PD-L1 positive rate was 45.1% (14/31). CONCLUSION: HAS represents a distinctive subtype of gastric cancer with a propensity for mimicking other forms of tumors, underscoring the significance of discerning its unique histopathological attributes for accurate differential diagnosis and tailored therapeutic interventions.