Clonal Status and Clinicopathological Features of Langerhans Cell Histiocytosis

Pulmonary Langerhans Cell Histiocytosis: An Update From the Pathologists' Perspective

CONTEXT

Pulmonary Langerhans cell histiocytosis (PLCH) is a rare histiocytic disorder that almost exclusively affects the lungs of smokers. PLCH is characterized by bronchiolocentric nodules and/or cysts in an upper and mid lung distribution with sparing of the costophrenic angles. The diagnosis can be challenging and often requires transbronchial biopsy or surgical lung biopsy. Pulmonary hypertension is a relatively common and sometimes severe complication of PLCH. The pathogenesis of PLCH is still debated. Recently, BRAF V600E mutation and BRAF expression have been identified in some patients with PLCH, suggesting that at least a subset of PLCH has a clonal proliferation. While smoking cessation is the first-line treatment of PLCH, some patients might require additional treatment and eventually transplant. Given that the lesional cells of PLCH express BRAF in some patients, MAPKinase pathway-targeted treatment might be useful for therapy-resistant patients.

OBJECTIVE

To present the more recently recognized clinical and pathologic aspects of PLCH, including pulmonary hypertension in PLCH, pathogenesis, and treatment, as well as the basic diagnostic approach to PLCH.

DATA SOURCES

Authors' own research, and search of literature database (PubMed) and UpToDate.

CONCLUSIONS

Despite the recent progress, more studies are needed to elucidate the biology of PLCH for identification of prognostic factors and appropriate treatment options, especially for therapy-refractory PLCH cases.

Polyclonal T-cells express CD1a in Langerhans cell histiocytosis (LCH) lesions

Langerhans cell histiocytosis (LCH) is a complex and poorly understood disorder that has characteristics of both inflammatory and neoplastic disease. By using eight-colour flow cytometry, we have identified a previously unreported population of CD1a(+)/CD3(+) T-cells in LCH lesions. The expression of CD1a is regarded as a hallmark of this disease; however, it has always been presumed that it was only expressed by pathogenic Langerhans cells (LCs). We have now detected CD1a expression by a range of T-cell subsets within all of the LCH lesions that were examined, establishing that CD1a expression in these lesions is no longer restricted to pathogenic LCs. The presence of CD1a(+) T-cells in all of the LCH lesions that we have studied to date warrants further investigation into their biological function to determine whether these cells are important in the pathogenesis of LCH.

High frequency of the X-chromosome inactivation in young female patients with high-grade glioma

BACKGROUND

Gliomas are common tumors and high-grade ones account for 62% of primary malignant brain tumors. Though current evidence have suggested that inherited risks play a role in glioma susceptibility, it was conveyed that glioma was such a complex disease, and the direct genetic contribution to glioma risk factors and its relation to other factors should be discussed more deeply. X-chromosome inactivation (XCI) is the mechanism by which gene dosage equivalence is achieved between female mammals with two X chromosomes and male mammals with a single X chromosome. As skewed XCI has been linked to development of some solid tumors, including ovarian, breast, and pulmonary and esophageal carcinomas, it is challenging to elucidate the relation of skewed XCI to high-grade gliomas development.

OBJECTIVE

The present study aimed to determine the general concordance between XCI pattern in blood cells and brain tissues, and SXCI frequencies in female patients with high-grade glioma compared to healthy controls.

METHODS

1,103 Chinese females without a detectable tumor and 173 female high-grade glioma patients, were detected in the study. Normal brain tissues surrounding the lesions in gliomas were obtained from 49 patients among the 173 ones, with the microdissection using a laser microdissection microscope Genomic DNA was extracted from the peripheral blood cells and the normal brain tissues from the subjects. Exon 1 of androgen receptor (AR) gene was amplified, and its products of different alleles were resolved on denaturing polyacrylamide gels and visualized after silver staining. The corrected ratios (CR) of the products before and after HpaII digestion were calculated.

RESULTS

Occurrence of SXCI was detected in both the patients and controls at similar frequencies. However, the phenomenon, as defined as CR ≥ 3, was more frequent in the patients aging ≤ 40 (23.6%) compared to the corresponding reference group (5.1%, P <0.0001). When CR ≥ 10 was adopted, the frequencies were 5.5% and 1.6%, respectively. Their difference did not attain statistical significance (P=0.10). When detected, both blood cells and brain tissue were compared after determination of a high concordance of XCI between blood cells and brain tissue collected from the same individuals (n=48, r =0.57, P <0.01).

CONCLUSIONS

The data from the current study demonstrated that SXCI may be a predisposing factor for development of high-grade glioma in young female patients and further study will verify its suitability as a biomarker to assess susceptibility of young female patients to high-grade glioma.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1935066233982578.

Diagnosis of Langerhans cell histiocytosis on fine needle aspiration cytology: a case report and review of the cytology literature

A case of multifocal Langerhans cell histiocytosis in a two-year-old child is presented where fine needle aspiration was helpful in achieving a rapid and accurate diagnosis in an appropriate clinical and radiological setting. This can avoid unnecessary biopsy and guide the management especially where access to histopathology is limited. The highly characteristic common and rare cytological features are highlighted with focus on differential diagnoses and causes of pitfalls.