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The reporting of lung neuroendocrine neoplasms (NENs) according to the 2021 World Health Organisation (WHO) is based on mitotic count per 2 mm2, necrosis assessment and a constellation of cytological and immunohistochemical details. Accordingly, typical carcinoid and atypical carcinoid are low‐ to intermediate‐grade neuroendocrine tumours (NETs), while large‐cell neuroendocrine carcinoma (NEC) and small‐cell lung carcinoma are high‐grade NECs. In small‐sized diagnostic material (cytology and biopsy), the noncommittal term of carcinoid tumour/NET not otherwise specified (NOS) and metastatic carcinoid NOS have been introduced with regard to primary and metastatic diagnostic settings, respectively. Ki‐67 antigen, a well‐known marker of cell proliferation, has been included in the WHO classification as a non‐essential but desirable criterion, especially to distinguish NETs from high‐grade NECs and to delineate the provisional category of carcinoid tumours/NETs with elevated mitotic counts (> 10 mitoses per mm2) and/or Ki‐67 proliferation index (≥ 30%). However, a wider use of this marker in the spectrum of lung NENs continues to be highly reported and debated, thus witnessing a never‐subsided attention. Therefore, the arguments for and against incorporating Ki‐67 in the classification and clinical practice of these neoplasms are discussed herein in detail. [ABSTRACT FROM AUTHOR]

Transformation optics is a powerful tool allowing remapping a generic domain into another yet maintaining a correspondence of the solution of Maxwell's equations within the two domains. Transformation optics has been used in the past to conveniently solve for modes in a generic waveguide by transforming its cross‐section into a circular one. Such a transformation needs particular care in enforcing boundary conditions in the transformed, circular, domain. In this paper, a theoretical treatment of boundary conditions is presented, allowing for an accurate computation of all field components in a generic waveguide. [ABSTRACT FROM AUTHOR]

This study introduces the conic section arc elements in 2D and 2.5D finite element method (FEM). Elements are obtained by deforming an edge in a standard triangular element through a coordinate transformation. This allows to completely eliminate the geometrical error in structures composed of circular, elliptical, hyperbolic and parabolic arcs. The element order is defined independently of the geometrical description of the boundary, allowing the use of simple meshers. Previously available FEM codes can be straightforwardly modified to introduce the conic section boundaries. [ABSTRACT FROM AUTHOR]