The 2015 World Health Organization Classification of lung tumors: new entities since the 2004 Classification.

In the last few years different new pulmonary neoplastic lesions have been recognised and some of them, namely NUT carcinoma, PEComatous tumors, pneumocytic adenomyoepithelioma, pulmonary myxoid sarcoma, myoepithelial tumors/carcinomas entered in the last 2015-WHO classification of lung tumors. In addition angiomatoid fibrous histiocytoma and ciliated muconodular papillary tumor have been morphologically and genetically characterized albeit not yet included in the 2015-WHO classification.In the present paper we summarised the clinical, morphological, immunohistochemical and molecular features of these new entities. The knowledge of key histologic and molecular characteristics may help pathologists in achieving a correct diagnosis thus leading to an adequate therapeutic approach.

Overexpression of Hypoxia-Inducible Factor-1α in Primary Graft Dysfunction Developing in an Orthotopic Lung Transplantation Rat Model.

BACKGROUND: Primary graft dysfunction (PGD) is the major cause of early morbidity and mortality after transplantation. A high rate of PGD is a frequent complication in orthotopic lung transplantation (OLT) models, which are currently used to investigate acute and chronic rejection pathways. Hypoxia-inducible factor (HIF)-1α is a heterodimeric αß transcription factor that mediates tissue response to hypoxia. In other solid organ transplantations, a significant correlation between HIF-1α expression and PGD was detected. To our knowledge no data are available on HIF-1α expression in PGD developing in lung transplantation. The aims of this study were to investigate HIF-1α expression (using immunohistochemistry) and correlate it to the main histological parameters related to ischemia-reperfusion (IR) injury, including terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) -positive apoptotic cells). METHODS: OLT was performed in 32 inbred rat strains and 11 of them died in the early postoperative period (from day 0-3) for IR injury. The histological and molecular evaluations were done in all lung tissues. Unimplanted donor rat lungs were used as controls. HIF-1α expression was correlated with all morphological parameters. RESULTS: Lung samples of animals with IR injury showed high scores of HIF-1α expression, edema, blood extravasation, granulocyte margination, apoptotic index, and necrosis in 91% of cases. Tissue overexpression of HIF-1α was detected in all lung samples with high scores of histological parameters and with high apoptotic indexes. CONCLUSION: Our data demonstrate that HIF-1α was overexpressed in more severe rat lung IR injury. The use of HIF-1α inhibitors could provide a translatable route into manipulating this complex system in vivo.

Activating c-KIT mutations in a subset of thymic carcinoma and response to different c-KIT inhibitors.

BACKGROUND: To analyze a multi-institutional series of type C thymic carcinomas (TCs) (including neuroendocrine tumors), focusing on the expression and mutations of c-KIT. MATERIALS AND METHODS: Immunohistochemical expression of c-KIT/CD117, p63, CD5 and neuroendocrine markers, as well as mutational analysis of c-KIT exons 9, 11, 13, 14, 17 by direct sequencing of 48 cases of TCs. Immunohistochemical and molecular data were statistically crossed with clinicopathological features. RESULTS: Overall, 29 tumors (60%) expressed CD117, 69% were positive for CD5 and 85% (41 cases) for p63. Neuroendocrine markers stained all six atypical carcinoids and five poorly-differentiated thymic squamous cell carcinomas. Overall, six CD117-positive cases (12.5%) showed c-KIT mutation. No mutation was detected in CD117-negative tumors and carcinoids. All the mutations were found in poorly-differentiated thymic squamous cell carcinomas expressing CD117, CD5, p63 and lacking neuroendocrine markers (6 of 12 cases with these features). Mutations involved exon 11 (four cases: V559A, L576P, Y553N, W557R), exon 9 (E490K) and exon 17 (D820E). CONCLUSIONS: All TCs need an immunohistochemical screening with CD117, while c-KIT mutation analysis is mandatory only in CD117-positive cases, particularly when coexpressing CD5 and p63, lacking neuroendocrine differentiation. The finding of c-KIT mutation can predict efficacy with different c-KIT inhibitors.

Pulmonary eosinophilic infiltrates.

Pulmonary eosinophilic infiltrates include an heterogeneous group of disorders characterized by the presence of eosinophils in the lungs as detected by bronchoalveolar lavage or tissue biopsy, with or without blood eosinophilia. The disease can be idiopathic (simple pulmonary eosinophilia, acute and chronic eosinophilic pneumonia, hypereosinophilic syndrome), secondary (to drugs, parasites, fungal and mycobacterial infection, irradiation, toxic products) or associated with diffuse lung diseases (connective tissue diseases and some neoplasms). Pathologists faced with eosinophils in the lungs (either on cytology or biopsy) should keep in mind several possibilities, although a diagnosis of certainty is rarely based on morphology alone. Correlation with laboratory tests, imaging studies and clinical presentation has a key role, even if some pulmonary eosinophilic diseases are sufficiently characteristic on clinico-radiologic ground to not require a biopsy (e.g. some drug reactions, parasitic infections, idiopathic hypereosinophilic syndrome, allergic bronchopulmonary aspergillosis). Nevertheless, pathologists can play a central role because they can be the first to note eosinophils in the lungs of a very sick patient. Knowledge of histologic features and a striking collaboration with other physicians are necessary to achieve correct diagnosis and to establish adequate treatments.

When histologic diagnosis of pulmonary adenocarcinoma becomes difficult.

The differential diagnosis between pulmonary adenocarcinoma and several benign mimics can be a formidable challenge for the surgical pathologist, particularly in frozen sections and in small biopsies but sometimes in surgical specimens as well. In this review we will provide a practical guide to help the pathologist facing these problematic cases.

Muscle recruitment with intrafascicular electrodes.

We have studied muscle recruitment with Teflon-insulated, 25 microns diameter, Pt-Ir intrafasicular electrodes implanted in nerves innervating the gastrocnemius and soleus muscles of cats. The purpose of this study was to measure the performance of these bipolar electrodes, which had been designed to optimize their ability to record unit activity from peripheral nerves, as stimulating electrodes. Recruitment curves identified the optimal stimulus configuration as a biphasic rectangular pulse, with an interphase separation of about 500 microseconds and a duration of about 50 microseconds. The current required for a half-maximal twitch contraction was on the order of 50 microA. Current and charge densities needed for stimulation were well below levels believed to be safe for the tissue and electrode materials involved. When the spinal reflex pathway was interrupted by crushing the nerve, the force produced by a given stimulus changed in some cases, but not in others, implying that the spinal reflex contribution was not the same in all the implants. We conclude that intrafascicular recording electrodes are also a potentially valuable technology for functional neuromuscular stimulation, and warrant further development.