The cover image is based on the Review New developments in mesothelial pathology by Andrew Churg, https://doi.org/10.1111/his.15007; the Review Updates on lung neuroendocrine neoplasm classification by Giulia Vocino Trucco et al., https://doi.org/10.1111/his.15058; and the Review Benign lesions of the mediastinum by Tiemo Sven Gerber et al., https://doi.org/10.1111/his.15088.

Classical and variant morphology of invasive mucinous adenocarcinoma.

Two-compartment model in the putative molecular pathogenesis of lung cancer. The accumulation of genetic alterations with escaping immune surveillance is a key factor for tumours from the air-conducting system under the strong influence of tobacco smoke, whereas oncogene-addicted adenocarcinomas are driven by a single oncogenic mutation with powerful transformation activity.

Highlights of major advances in lung neuroendocrine neoplasm classification, including the introduction of NET G3 in the classification framework, the potential impact of Artificial Intellignce, and the identification of novel prognostic molecular biomarkers.

This review provides an update on NUT carcinoma and thoracic SMARCA4-deficient undifferentiated tumor, including their key clinicopathological/molecular characteristics and controversies.

An example of mesothelioma in situ, a new entity discussed in this review.

Grading of epithelioid mesothelioma is now recommended and is a powerful prognostic tool. Grading requires calculation of an atypia score and mitotic count score which yields a nuclear grade that is combined with the presence or absence of necrosis to determine overall grade (low or high).

Thymic hyperplasia with lymphoepithelial sialadenitis (LESA)-like features as an example of a thymic tumorous lesion showing an association with non-myasthenic autoimmune diseases and lymphomas.

In this review, the various subtypes of thymic epithelial tumours are described, with attention to differential diagnosis and ancillary techniques, as well as limitations of biopsy and frozen section diagnosis, and the clinical relevance for prognosis and treatment.

Primary mediastinal germ cell tumours encompass five histological subtypes: seminoma, embryonal carcinoma, teratoma, yolk-sac tumour and choriocarcinoma. Seminomas consist of medium-sized cells with clear to eosinophilic cytoplasm and prominent nucleoli. Embryonal carcinomas with solid growth pattern, sometimes glandular or papillary growth pattern, contain pleomorphic cells with overlapping nuclei and prominent nucleoli. Teratomas can show differentiation of all three germ cell layers, usually forming cysts lined by squamous, respiratory, or intestinal epithelium. Solid areas contain pancreatic tissue, fat tissue, and smooth muscles. Yolk-sac tumours can show different growth patterns with reticular growth pattern as the most common. Choriocarcinomas consist of bilamellar structures of mononucleated cytotrophoblasts and multinucleated syncytiotrophoblasts.

Schwannoma of the posterior mediastinum. This is the most common neural tumour of the mediastinum. The gross and microscopic aspect is similar in every respect to Schwannoma's of soft tissue elsewhere.