Improving the Laboratory Diagnosis of M-like Variants Related to Alpha1-Antitrypsin Deficiency.

Alpha1-antitrypsin (AAT) is a serine protease inhibitor that is encoded by the highly polymorphic SERPINA1 gene. Mutations in this gene can lead to AAT deficiency (AATD), which is associated with an increased risk of lung and/or liver disease. On the basis of electrophoretic migration, AAT variants are named with capital letters; M (medium) signifies the normal protein. Among pathological variants, the M-like ones represent a heterogeneous group of rare allelic variants that exhibit the same electrophoretic pattern as the M wild-type protein, which makes them difficult to detect with routine methods. In order to avoid their misdiagnosis, the present study defines and validates effective methods for the detection of two pathogenic M-like variants, Mwurzburg and Mwhitstable. Comparison of protein phenotypes using isoelectric focusing of samples that presented the Mwurzburg variant, as revealed by exons 5 sequencing, identified a particular electrophoretic pattern amenable to the Mwurzburg protein. The specific phenotyping pattern was retrospectively validated, thus enabling the detection of 16 patients with Mwurzburg variant among the subjects already tested but not sequenced according to our diagnostic algorithm. The Mwhitstable allele was detected by intron 4 sequencing of SERPINA1 gene. Mwurzburg and Mwhitstable are often misdiagnosed and the introduction of diagnostic improvements can help the clinical management, especially in patients with established lung disease without any other reported risk factors.

The growth of non-solid neoplastic lung nodules is associated with low PD L1 expression, irrespective of sampling technique.

BACKGROUND: Few data are known regarding the molecular features and patterns of growth and presentation which characterize those lung neoplastic lesions presenting as non-solid nodules (NSN). METHODS: We retrospectively reviewed two different cohorts of NSNs detected by CT scan which, after transthoracic fine-needle aspiration (FNA) and core needle biopsy (CNB) received a final diagnosis of malignancy. All the enrolled patients were then addressed to surgical removal of lung cancer nodules or to exclusive radiotherapy. Exhaustive clinical and radiological features were available for each case. RESULTS: In all 62 analysed cases the diagnosis of adenocarcinoma (ADC) was reached. In cytologic samples, EGFR activating mutations were identified in 2 of the 28 cases (7%); no case showed ALK/EML4 or ROS1 translocations. In the histologic samples EGFR activating mutation were found in 4 out of 25 cases (16%). PD-L1 immunostains could be evaluated in 30 cytologic samples, while the remaining 7 did not reach the cellularity threshold for evaluation. TPS was < 1% in 26 cases, > 1% < 50% in 3, and > 50% in 1. All surgical samples showed TPS < 1%. Of the 17 cases that could be evaluated on both samples, 15 were concordantly TPS 0, and 2 showed TPS > 1% < 50 on the biopsy samples. TPS was < 1% in 14 cases, > 1%/< 5% in 4 cases, > 5%/< 50% in 2 cases, > 50% in 1 case. CONCLUSIONS: Overall PD-L1 immunostaining documented the predominance of low/negative TPS, with high concordance in FNA and corresponding surgical samples. It can be hypothesized that lung ADC with NSN pattern and predominant in situ (i.e. lepidic) components represent the first steps in tumor progression, which have not yet triggered immune response, and/or have not accumulated a significant rate of mutations and neoantigen production, or that they belong to the infiltrated-excluded category of tumors. The negative prediction of response to immunomodulating therapy underlines the importance of rapid surgical treatment of these lesions. Notably, cell block cytology seems to fail in detecting EGFR mutations, thus suggesting that this kind of sampling technique should be not adequate in case of DNA direct sequencing.