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The development of immune checkpoint inhibitor (ICI) therapy with anti-CTLA-4 and anti-PD-1/L1 monoclonal antibodies has led to a paradigm shift in cancer therapy. ICI neoadjuvant therapy followed by surgery has become the standard of care for several advanced-stage cancers. The pathology associated with ICI therapy is vast and includes neoadjuvant-associated tissue reactions and activation of tertiary lymphoid structures (TLSs) at the site of the tumor bed and off-target immune-related adverse events (irAEs). TLSs are thought to recapitulate lymph node function and may act as localized immune machinery to mount an antitumor response. B cell activation in TLSs during neoadjuvant ICI therapy has been correlated with antitumor response. We report a patient with a history of sarcomatoid squamous cell carcinoma treated with neoadjuvant ICI cemiplimab who developed clonal expansion of B cells in the TLSs of the tumor bed. The TLSs morphologically mimicked a low-grade B cell lymphoma with plasmacytic differentiation. Awareness of clonal expansion of B cells in TLSs during neoadjuvant ICI therapy is critical to recognize a response to ICI therapy and to avoiding an incorrect diagnosis of low-grade B cell lymphoma. This article is protected by copyright. All rights reserved.

Naive T helper cells differentiate into functionally distinct effector subsets that drive specialized immune responses. Recent studies indicate that some of the effector subsets have plasticity. Here, we used an EAE model and found that Th17 cells deficient in the transcription factor BCL11B upregulated the Th2-associated proteins GATA3 and IL-4 without decreasing RAR-related orphan receptor γ (RORγt), IL-17, and GM-CSF levels. Surprisingly, abnormal IL-4 production affected Th17 cell trafficking, diverting migration from the draining lymph nodes/CNS route to the mesenteric lymph nodes/gut route, which ameliorated EAE without overt colitis. T helper cell rerouting in EAE was dependent on IL-4, which enhanced retinoic acid (RA) production by dendritic cells, which further induced expression of gut-homing receptors CCR9 and α4β7 on Bcl11b-deficient CD4+ T cells. Furthermore, IL-4 treatment or Th2 immunization of wild-type mice with EAE caused no alteration in Th17 cytokines or RORγt, but diverted T helper cell trafficking to the gut, which improved EAE outcome without overt colitis. Our data demonstrate that Th17 cells are permissive to Th2 gene expression without affecting Th17 gene expression. This Th17 plasticity has an impact on trafficking, which is a critical component of the immune response and may represent a possible avenue for treating multiple sclerosis.

Carcinomas arising from breast hamartomas are exceedingly rare. We present the first reported case of an African-American female presenting with a right breast lump and a subsequent mammogram suggestive of a hamartoma. She later underwent lumpectomy and was found to have HER2+ invasive ductal carcinoma (IDC) arising from a hamartoma. She was amenable to HER2-targeted trastuzumab, hormone therapy and adjuvant radiation but declined chemotherapy. In a review of the literature, IDC is the predominant neoplastic type found in hamartomas. The average hamartoma size at time of neoplasm diagnosis is 6.0 cm. Patients with hamartomas greater than 6.0 cm, with changes in calcification pattern; new nodules or asymmetry should be considered for additional evaluation with ultrasound, MRI and/or biopsy. HER2 status is under-reported among cases and should be evaluated in any malignancy found within hamartomas as HER-2 therapy has improved overall survival and recurrence free survival in HER2+breast cancer patients.

Mixed neuroendocrine-nonneuroendocrine neoplasms (MiNENs) are a group of rare tumors previously known as mixed adenoneuroendocrine carcinomas (MANECs). The neuroendocrine component is high-grade and may consist of small-cell carcinoma or large-cell neuroendocrine carcinoma. The nonneuroendocrine component may consist of adenocarcinoma or squamous cell carcinoma. We report a unique case of a MiNEN with trilineage differentiation: large-cell neuroendocrine carcinoma, squamous cell carcinoma, and adenocarcinoma. The reported patient presented with symptoms of an upper gastrointestinal bleed and was ultimately diagnosed with a MiNEN with trilineage differentiation. This is the first report of this exceedingly rare tumor type to include next-generation sequencing of the 3 separate tumor entities. In addition, we review the current literature and discuss the role of next-generation sequencing in classifying and treating MiNEN tumors.

Dermatomyositis with subcutaneous edema is a rare process with few reported cases. We report a 63-year-old with lung cancer who presented with an erythematous skin rash and was found to have biopsyproven dermatomyositis. Her course was complicated by generalized edema, myalgias, muscle weakness, dysphagia, and laryngeal edema. The edema was severe and caused respiratory distress requiring intubation. The patient underwent therapy with high-dose glucocorticoids and intravenous immunoglobulin but failed treatment. Altogether, she presented as an extreme case and rare variant of dermatomyositis, known as edematous dermatomyositis. Diagnostic and treatment guidelines do not account for this variant and literature pertaining to edematous dermatomyositis is sparse. Moreover, this disease was a paraneoplastic manifestation of her small cell lung cancer, which is rarely observed. There are no cases reporting edematous dermatomyositis as a paraneoplastic manifestation of small cell lung cancer, and we highlight the high rate of morbidity and mortality in such patients.