Imaging Phenotypes and Evolution of Hepatic Langerhans Cell Histiocytosis on CT/MRI: A Retrospective Study of Clinical Cases and Literature Review

(1) Background: pathological changes in hepatic Langerhans cell histiocytosis (LCH) have been observed; however, corresponding imaging findings can appear vague to physicians and radiologists. The present study aimed to comprehensively illustrate the imaging findings of hepatic LCH and to investigate the evolution of LCH-associated lesions. (2) Methods: LCH patients with liver involvement treated at our institution were retrospectively reviewed along with prior studies in PubMed. Initial and follow-up computed tomography (CT) and magnetic resonance imaging (MRI) were systematically reviewed, and three imaging phenotypes were created based on the lesion distribution pattern. Clinical features and prognoses were compared among the three phenotypes. Liver fibrosis was evaluated visually on T2-weighted imaging (T2WI) and diffusion-weighted imaging (DWI), and apparent diffusion coefficient (ADC) values of the fibrotic areas were measured. Descriptive statistics and a comparative analysis were used to analyze the data. (3) Results: based on the lesion distribution pattern on CT/MRI scans, patients with liver involvement were categorized as the disseminated lesion phenotype, scattered lesion phenotype, and central periportal lesion phenotype. Patients with scattered lesion phenotype were typically adults, and only a few of them had hepatomegaly (n_present = 1, 1/6, 16.7%) and liver biochemical abnormalities (n_present = 2, 2/6, 33.3%); patients with central periportal lesion phenotype were typically young children, and hepatomegaly and biochemical abnormalities were more apparent in these patients than those with another phenotype; and those with the disseminated lesion phenotype were found in all age groups, and the lesions evolved rapidly on medical imaging. Follow-up MRI scans show more details and can better document the evolution of lesions than CT. T2-hypointense fibrotic changes, including the periportal halo sign (n_present = 2, 2/9, 22.2%), patchy liver parenchyma changes (n_present = 6, 6/9, 66.7%), and giant hepatic nodules close to the central portal vein (n_present = 1, 1/9, 11.1%), were found, while fibrotic changes were not observed in patients with the scattered lesion phenotype. The mean ADC value for the area of liver fibrosis in each patient was lower than the optimal cutoff for significant fibrosis (METAVIR Fibrosis Stage ≥ 2) in a previous study that assessed liver fibrosis in chronic viral hepatitis. (4) Conclusions: The infiltrative lesions and liver fibrosis of hepatic LCH can be well characterized on MRI scans with DWI. The evolution of these lesions was well demonstrated on follow-up MRI scans.

Langerhans Cell Histiocytosis and Langerhans Cell Sarcoma: Current Understanding and Differential Diagnosis

Langerhans cell (LC) histiocytosis (LCH) and LC sarcoma (LCS) are proliferative processes consisting of cells having morphologic and phenotypic features of Langerhans cells (LCs), although the latter may have lost some of these features. Because neoplastic nature of LCH as well as LCS is more likely by recent studies, a category of LC hyperplasia can be better characterized. LCH and LCS are rarely seen in daily pathology practice, but it is important to accurately characterize these lesions. For this purpose, an outline covering proliferations of LC and related cells was constructed. The scheme of this outline is based especially on evaluating borderline lesions, neoplastic trans-differentiation, and degree of similarity with the normal counter-parts. In addition, the organization and update of the current classification scheme for histiocytic and dendritic-cell proliferations is presented.

[Eosinophilic granuloma of the parietal bone of an adult patient with BRAF mutation]

The paper describes a case of eosinophilic granuloma of the parietal bone in a 32-year-old man. Histological examination revealed a large number of bean-shaped Langerhans cell histiocytes with lobed nuclei and nuclear grooves. The histiocytes alternated with the foci of obvious eosinophilic infiltration and with eosinophilic microabscesses. There were osteoclast-like multinucleated giant cells, bone resorption, and numerous bone rods covered with osteoblast chains. The histiocytes expressed CD1α, langerin, CD68, S100, and p53 (in 90.0% of the tumor cells). The Ki-67 proliferation index was 18.0%. A molecular genetic study identified BRAFV600E mutation (nucleotide substitution s.1799 T>A (p.V600E) in the heterozygous state). Clinical and morphological data and the results of molecular genetic studies led to the conclusion that there was eosinophilic granuloma of the right parietal bone (the unifocal form of Langerhans cell histiocytosis (LCH), type I, group A1, with the monoossal nature of lesion and with BRAFV600E mutation). In adults, this disease is extremely rare (2-5 cases of LCH per million people, bone loss in the fourth decade of life in 2.5% of the patients).

Recent advances in Langerhans cell histiocytosis

The purpose of this review is to provide an updated overview of the pathogenesis and treatment of Langerhans cell histiocytosis (LCH). The pathogenesis of LCH remains obscure and the optimal treatment for LCH has not been established, although incremental progress has been made. Proinflammatory cytokines and chemokines are known to play a role in LCH, which suggests that LCH is an immune disorder. However, the oncogenic BRAF mutation is also detected in more than half of LCH patients, which suggests that LCH is a neoplastic disorder. Remaining major issues in the treatment of LCH are how to rescue patients who have risk-organ involvement but do not respond to first-line therapy, the optimal treatment for the orphan disease of multifocal adult LCH, and how to reduce and treat central nervous system-related consequences, such as central diabetes insipidus and neurodegeneration. More research is needed to better understand the pathogenesis of this disease and to resolve the treatment issues.

Frequent BRAFV600E mutation has no effect on tumor invasiveness in patients with Langerhans cell histiocytosis

The oncogenic BRAF^V600E mutation in patients with Langerhans cell histiocytosis (LCH) has recently been reported. However, the reported frequencies were significantly inconsistent and were based on studies of populations of western ethnic origin. The aim of this study was to identify the presence of BRAF^V600E mutation in a cohort of Chinese LCH patients and to determine its association with clinicopathological characteristics. Blocks were retrieved from 52 LCH patients and 12 samples were obtained from blood or bone marrow. These were tested for BRAF^V600E by directly sequencing the entire exon 15 of the BRAF gene. To demonstrate the relationship between BRAF^V600E and invasiveness of LCH, the single or multiple systems classification was used. BRAF^V600E was the only genetic abnormality within exon 15 of the BRAF gene in patients with LCH. Its incidence was 56%, similar to that reported in a United States study, but higher than that reported in German studies. Additionally, the frequencies were similar between patients with single system diseases and those with multiple system diseases. Results of this study showed that BRAF^V600E was present in a large number of the Chinese LCH patients, confirming the neoplastic nature of LCH. The frequency was similar to that of the USA study but distinctly higher than that from the Europe studies. No additional mutation were identified besides BRAF^V600E. This mutation did not closely correlate with clinical severity or classification. The finding of BRAF^V600E in LCH has important implications for both molecular diagnosis and targeted personalized therapy.