Kikuchi-Fujimoto disease type lymph node reaction with increased plasmacytoid dendritic cells may appear as a side effect following COVID-19 vaccination: Report of a case and literature review.

Subsequent to mass vaccination programs against COVID-19, diverse side effects have been described, both at the injection site, such as pain, redness and swelling, and systemic effects such as fatigue, headache, muscle or joint pain. On rare occasions, a lymphadenopathic syndrome may develop, raising the clinical suspicion of a lymphoproliferative disorder. We present the case of a 30-year-old woman who developed self-limiting left axillary lymphadenopathy following COVID-19 vaccination. To date, only seven similar cases with a complete clinicopathological description have been published, and fourteen cases have been notified to the European adverse events databases (Eudravigilance) in relationship with vaccination against COVID-19. It is important to be aware of this potential complication when a lymphadenopathic syndrome develops following vaccination, to avoid unnecessary treatment.

CTNNB1 somatic mutations drive Wnt pathway activation in a case of incidental intranodal palisaded myofibroblastoma.

Intranodal palisaded myofibroblastoma (IPM) is a rare stroma-derived spindle-cell neoplasm of the lymph node with myofibroblastic differentiation and CTNNB1 (ß-catenin gene) somatic mutations. We present a case of IPM found incidentally in the staging of lung adenocarcinoma. We describe the major histopathological and phenotypic features, including a palisaded bland spindle cell proliferation with myofibroblastic differentiation and Wnt pathway activation by immunohistochemistry, including ß-catenin expression. Production of osteoid-like collagen directly from tumor cells was observed. We confirmed p.Gly34Arg CTNNB1 mutation by direct sequencing. We also reviewed the literature for similar cases.