The mismatch repair system is a major pathway that functions in the maintenance of genomic integrity. It is involved in mitotic and meiotic recombination, apoptosis, immunoglobulin gene rearrangement, somatic hypermutation, and other processes. Deficiencies in mismatch repair give rise to hypermutability and the phenomenon called microsatellite instability. Detection of deficient mismatch repair function or microsatellite instability is used diagnostically, predictively, and prognostically. Specifically, deficient mismatch repair function is used for screening of Lynch syndrome, determining patients who are likely to respond to immune checkpoint inhibition, and to contributes to an understanding of which cancer patients may pursue a more aggressive clinical course. Microsatellite instability can be evaluated directly by polymerase chain reaction (PCR) or indirectly by assessment of mismatch repair protein expression using immunohistochemistry (IHC), and mismatch repair function using next-generation sequencing assays which evaluates homopolymer indels. In this article, we provide a concise practical review on mismatch repair deficiency (MMR-d)/ microsatellite instability (MSI), focusing on clinical testing, different testing methods, interpretation of findings, the predictive, and prognostic utility of MSI.

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Fusion genes have been identified in a wide array of human neoplasms including hematologic and solid tumors, including gastrointestinal tract neoplasia. A fusion gene is the product of parts of two genes that are joined together following a deletion, translocation, or chromosomal inversion. Together with single nucleotide variants, insertions, deletions, and amplification, fusion genes represent one of the key genomic mechanisms for tumor development. Detecting fusions in the clinic is accomplished by a variety of techniques including break‐apart fluorescence in situ hybridization, reverse transcription‐polymerase chain reaction, and next‐generation sequencing. Some recurrent gene fusions have been successfully targeted by small molecule or monoclonal antibody therapies (ie targeted therapies), while others are used as biomarkers for diagnostic and prognostic purposes. The purpose of this review article is to discuss the clinical utility of detection of gene fusions in carcinomas and neoplasms arising primarily in the digestive system.

Background Syphilis infections are increasing globally. Lower gastrointestinal syphilis (LGIS) is a rare manifestation of early syphilis transmitted through anal sexual contact. Misdiagnosis of LGIS as inflammatory bowel disease may result from clinician under-awareness. Methods We searched the literature for articles describing cases of LGIS, and identified additional cases diagnosed within our institution. Data were extracted from the articles and medical records and analyzed to provide a summative account. Results 54 cases of LGIS were identified in 39 articles published between 1958 and 2020. 8 additional cases were diagnosed at our institution between 2011 and 2020, totaling 62 cases. All cases were described in men and transwomen aged 15 to 73 years. 50 (93%) individuals endorsed having sex with men. In 26 cases (52%) individuals were HIV co-infected. LGIS presented most commonly with hematochezia (67%) and anal pain (46%). The most common physical exam findings were rectal mass (38%), lymphadenopathy (31%), and rash (26%). Non-treponemal titers ranged from 1:2-1:1024. Of the 52 cases in which endoscopy was reported, 22 (42%) showed anorectal mass and 18 (35%) showed anorectal ulcer. In 44 cases (75%), histopathology revealed a chronic inflammatory infiltrate with a prominent lymphocyte component (45%) and/or plasma cells (36%). 78% of specimens to which a tissue stain was applied were positive for spirochetes. Conclusions LGIS should be suspected in men and transwomen presenting with a lower gastrointestinal symptom or mucosal abnormality. A sexual history must be elicited and guide testing. Misdiagnosis can delay treatment and threatens patient and public health.

Background: INSURE (Intubation, Surfactant administration, and Extubation) therapy is controversial in managing respiratory distress syndrome (RDS) in late preterm newborns. This study aims to determine whether the use of the INSURE in late preterm infants with RDS is associated with improved outcomes compared to similar infants managed with CPAP alone. Methods: A retrospective cohort study compared two different neonatal care units with two different treatments of RDS in late preterm infants in Bucaramanga, Colombia. One cohort used selective bubble CPAP and rescue surfactant, the second cohort used selective bubble CPAP and INSURE within the first hour of life. We included all the newborns with gestational age between 33 - 366/7 weeks, born between 2012 to 2017, that developed early RDS and were treated with CPAP.  Results: We recruited 208 patients   (57 CPAP and rescue surfactant and 151 CPAP + INSURE).  Early INSURE was reported in 117 patients (56.3 %). INSURE therapy was associated with a reduced risk of CPAP failure (RR = 0.50; 95 % CI 0.26 - 0.98); this effect was evident only when surfactant was administered within the first two hours of life (RR = 0.29; 95 % CI 0.12 - 0.69). Early INSURE was associated with a decreased risk of pneumothorax (RR = 0.07; 95 % CI 0.01 - 0.77) and pulmonary hypertension (RR = 0.34; 95 % CI 0.14 - 0.78). Conclusions: Early INSURE therapy was associated with a reduced incidence of CPAP failure, pneumothorax, and pulmonary hypertension in late preterm infants with moderate to severe RDS. Large, well-powered randomized controlled trials are needed to confirm these observations, but its use is supported by studies with similar results in more premature infants.