Immunomolecular and reactivity landscapes of gut IgA subclasses in homeostasis and inflammatory bowel disease.

The human gut includes plasma cells (PCs) expressing immunoglobulin A1 (IgA1) or IgA2, two structurally distinct IgA subclasses with elusive regulation, function, and reactivity. We show here that intestinal IgA1+ and IgA2+ PCs co-emerged early in life, comparably accumulated somatic mutations, and were enriched within short-lived CD19+ and long-lived CD19- PC subsets, respectively. IgA2+ PCs were extensively clonally related to IgA1+ PCs and a subset of them presumably emerged from IgA1+ precursors.

Decoding -ITD Sarcomas: Case Report of a Rare Pediatric Tumor With Challenges in Diagnosis.

Sarcomas characterized by gene alterations, are a distinct clinico-pathological group of high-grade tumors, that represent 5% of small round cell tumors without or fusion. Diverse genetic alterations characterize this group, including gene fusion being the most common alteration and less frequently internal tandem duplications (ITDs). We present a compelling case of a 3-year-old girl diagnosed with a high-grade nasoethmoidal sarcoma exhibiting -ITD.

RAF1 gene fusions are recurrent driver events in infantile fibrosarcoma-like mesenchymal tumors.

Infantile fibrosarcomas (IFS) and congenital mesoblastic nephroma (CMN) are rare myofibroblastic tumors of infancy and early childhood commonly harboring the ETV6::NTRK3 gene fusion. IFS/CMN are considered as tumors with an 'intermediate prognosis' as they are locally aggressive, but rarely metastasize, and generally have a favorable outcome. A fraction of IFS/CMN-related neoplasms are negative for the ETV6::NTRK3 gene rearrangement and are characterized by other chimeric proteins promoting MAPK signaling upregulation.

Pediatric Plexiform Fibromyxoma: A Case Report.

The plexiform fibromyxoma is a rare mesenchymal tumor in adults that generally originates in the antrum of stomach, being its occurrence in pediatric patients exceptional. It was classified as a distinct entity by World Health Organization in 2010. No recurrences and metastases have been documented in many of the reported patients to date, being the surgical treatment curative.