Implementing an integrated molecular classification for gastric cancer from endoscopic biopsies using on-slide tests.

The availability of more effective biological therapy can improve outcomes of gastric cancer (GC), but most patients do not have access to personalized treatment. GC molecular classification helps identify patients suitable for specific therapies and provides useful prognostic information. To date, only a small number of patients have access to molecular classification. We proposed a working molecular classification that can be delivered using on-slide tests available in most histopathology laboratories. We used eight on-slide tests [in situ hybridization (ISH) for Epstein-Barr virus-encoded small ribonucleic acid (EBER) and immunohistochemistry (IHC) for MutL homolog 1 (MLH1), PMS1 homolog 2 (PMS2), MutS homolog 2 (MSH2), MutS homolog 6 (MSH6), E-cadherin, ß-catenin and p53] to classify GC into one of six categories: GC associated with Epstein-Barr virus (GC-EBV), GC mismatch repair deficient (GC-dMMR), GC with epithelial-mesenchymal transition (GC-EMT), GC with chromosomal instability (GC-CIN), GC genomically stable (GC-GS) and GC not otherwise specified (GC-NOS)∕indeterminate. The classification has provision also for current and future on-slide companion diagnostic (CDx) tests necessary to select specific biological therapies and, as proof of principle, in this study we used three CDx tests currently required for the management of GC [human epidermal growth factor receptor 2 (Her2), programmed cell death-ligand 1 (PD-L1) 22C3 and Claudin18.2 (CLDN18.2)]. This paper describes the necessary tissue pathways and laboratory workflow and assesses the feasibility of using this classification prospectively on small endoscopic biopsies of gastric and gastroesophageal junction adenocarcinoma. This work demonstrates that such molecular classification can be implemented in the context of a histopathology diagnostic routine with little impact on turnaround times and laboratory capacity. The widespread adoption of a molecular classification for GC will help refine prognosis and guide the choice of more appropriate biological therapy for these patients.

Cutaneous microcystic/reticular schwannoma: case report and literature review of an exceedingly rare entity with an unusual presentation.

Conventional schwannoma represents a benign peripheral nerve sheath tumor derived from Schwann cells, which usually arises in the fourth or fifth decade of life, in the subcutaneous tissue of the distal extremities, or in the head and neck region of adult patients, with no gender predilection. In addition to the classic type, at least 11 different histopathological subtypes have been described and unawareness of these uncommon histopathological entities may lead to diagnostic pitfalls and risk of mistreatment. Recently described in the scientific literature, microcystic/reticular schwannoma is still relatively unknown to both surgeons and pathologists. The purpose of this paper is to highlight its existence by describing an additional case that occurred in the retroauricular area, and to further characterize its clinical, histopathological and immunohistochemical features. We reviewed the literature and compared the current case with others that have been documented thus far, discussing all possible differential diagnoses.

Keratoacanthoma centrifugum marginatum: an unusual clinical and histopathological diagnostic pitfall.

Keratoacanthoma centrifugum marginatum (KCM) is a very rare variant of keratoacanthoma characterized by progressive peripheral growth accompanied by central healing. The tumor has the peculiar ability to involute spontaneously. A careful differential diagnostic with other skin carcinomas or hyperkeratotic lesions is required in order to ensure appropriate clinical management. We report a case of KCM in a 62-year-old man presenting with a solitary, large exophytic, sessile tumor located on the ventral side of the right lower leg, which developed over the course of one year from an initial erythematous papule. The patient presented history of local trauma. To our knowledge, this is the second report in the scientific literature supporting a possible traumatic etiology. Due to its rarity and lack of distinctive histopathological features, KCM poses a difficult diagnostic challenge. Therefore, the importance of an accurate histopathological examination and extensive use of ancillary studies for differential diagnosis is emphasized.