Bronchioloalveolar adenocarcinoma and pulmonary langerhans cell histiocytosis in a patient with MUTYH-associated polyposis

Phenotype correlations with pathogenic DNA variants in the MUTYH gene

MUTYH -associated polyposis (MAP) is an autosomal recessive disorder where the inheritance of constitutional biallelic pathogenic MUTYH variants predisposes a person to the development of adenomas and colorectal cancer (CRC). It is also associated with extracolonic and extraintestinal manifestations that may overlap with the phenotype of familial adenomatous polyposis (FAP). Currently, there are discrepancies in the literature regarding whether certain phenotypes are truly associated with MAP. This narrative review aims to explore the phenotypic spectrum of MAP to better characterise the MAP phenotype. A literature search was conducted to identify articles reporting on MAP-specific phenotypes. Clinical data from 2109 MAP patients identified from the literature showed that 1123 patients (53.2%) had CRC. Some patients with CRC had no associated adenomas, suggesting that adenomas are not an obligatory component of MAP. Carriers of the two missense founder variants, and possibly truncating variants, had an increased cancer risk when compared to those who carry other pathogenic variants. It has been suggested that somatic G:C>T:A transversions are a mutational signature of MAP, and could be used as a biomarker in screening and identifying patients with atypical MAP, or in associating certain phenotypes with MAP. The extracolonic and extraintestinal manifestations that have been associated with MAP include duodenal adenomas, duodenal cancer, fundic gland polyps, gastric cancer, ovarian cancer, bladder cancer and skin cancer. The association of breast cancer and endometrial cancer with MAP remains disputed. Desmoids and Congenital Hypertrophy of the Retinal Pigment Epithelium (CHRPEs) are rarely reported in MAP, but have long been seen in FAP patients, and thus could act as a distinguishing feature between the two. This collection of MAP phenotypes will assist in the assessment of pathogenic MUTYH variants using the American College of Medical Genetics and the Association for Molecular Pathology (ACMG/AMP) Variant Interpretation Guidelines, and ultimately improve patient care.

Langerhans Cell Histiocytosis-Associated Pulmonary Adenocarcinoma: A Word of Caution during Molecular Determinations

Background: Smoking habit is a common cause of pulmonary Langerhans cell histiocytosis (PLCH) and lung cancer and both diseases may coexist in the lung and share genetic alterations, such as V600E BRAF mutations. We collected a small series of three cases of PLCH-associated lung adenocarcinoma in order to evaluate the molecular setup in both components and underline the critical role of careful tissue selection for predictive molecular driver testing. Methods: Three cases of PLCH-associated adenocarcinoma were collected from consultation files. Clinical data from referring physicians and clinical data were obtained. The surgical biopsies were tested by immunohistochemistry and molecular analysis after separate dissection of adenocarcinoma cells and Langerhans histiocytes. Results: There were three active smoking men with a median age at diagnosis of 60.6 years. PLCH was disclosed at imaging during work-up for suspected lung cancer. Molecular analysis revealed KRAS (G12C and G13C) mutations in two cases and V600E BRAF mutation in one case of PLCH. Immunostaining with the V600E BRAF mutation specific primary antibody VE1 correctly recognized BRAF-mutated LCH. One case was wild-type in both diseases. Two similar cases were found in the literature, one of which showed a discrepant KRAS (G12D) mutation in adenocarcinoma and a V600E BRAF mutation in LCH; Conclusions: This case series of PLCH-associated adenocarcinoma underline the possibility to disclose identical genetic alterations in co-existing benign and malignant pathologies, then potentially creating erroneous interpretation of molecular analysis leading to inadequate therapeutic options in case of incorrect diagnostic recognition and inappropriate selection of both components through microdissection.

Genomic alterations in pulmonary adenocarcinoma in situ in an adolescent patient

Lung cancer is a rare event in the pediatric and adolescent population. To date, only a few case reports and small case series have been published, and little is known about the risk factors associated with this entity in children and adolescents. We describe a case of adenocarcinoma in situ in a 15-year-old adolescent girl with previous surgical treatment for malignant melanoma. We provide a detailed genomic characterization of this neoplasm by comparative genomic hybridization, genome-wide single-nucleotide polymorphism array, and fluorescence in situ hybridization analyses. We identify chromosomal regions with copy number changes and correlate the corresponding genes within these regions with the available literature in the area.