Mediastinal Rosai-Dorfman Disease with KRAS mutation case report and literature review.

Rosai-Dorfman Disease (RDD) is a rare self-limiting histiocytosis, more prevalent in children and young adults. It typically manifests as painless bilateral massive cervical lymphadenopathy but may also extend to extra-nodal sites, with intrathoracic RDD noted in 2% of cases. Distinguishing mediastinal RDD from thymoma on imaging poses challenges, underscoring the reliance on pathological features and immunohistochemical staining for diagnosis. Patient, male, 33 years old, underwent lung a CT revealing an enlarged round soft tissue shadow in the anterior superior mediastinum, compared to a year ago. Surgical resection removed the entire mass, thymus, and part of the pericardium, confirming RDD on pathology. Genetic testing using second-generation testing technology identified a KRAS gene point mutation. No established treatment protocol currently exists for this disease. However, as genetic mutation research progresses, a novel therapeutic avenue is emerging: targeted therapy integrated with surgical interventions.

Zhang W ，Fang L ，Wang J ，Ma X ，Hu X ，Liu W ... -  《Journal of Cardiothoracic Surgery》

Recurrent central nervous system Rosai-Dorfman disease with KRAS mutation: a case report.

Rosai-Dorfman disease (RDD) is a rare, non-Langerhans cell histiocytosis of unknown etiology. we report a very rare case of recurrent central nervous system RDD with KRAS gene mutation and review the literature to improve our understanding of this disease. A 19-year-old male patient was admitted to our hospital for headache. Cranial magnetic resonance imaging revealed a mass of abnormal signal shadows in the prepontine cistern. The mass was surgically removed and the patient was consequently diagnosed with intracranial Rosai-Dorfman disease. Seven months later, pathological examination confirmed that the RDD had recurred. Next-generation sequencing found KRAS mutation in exon 4 (C.351A > C. P. K117n). RDD of the CNS has no distinct clinical manifestations and imaging characteristics, and the final diagnosis should be based on the results of the pathological examination. Although RDD is not currently classified as a neoplastic disorder, some evidence of clonality has changed our understanding of it. Follow up examinations over a long period are necessary to determine the efficacy of treatment.

Wang Q ，Ren H ，Zheng L ，Wang J ，Zhong D ... -  《Diagnostic Pathology》

A meta-analysis of cases of Rosai Dorfman disease reported on the African continent and a description of two cases from a tertiary academic hospital in Johannesburg, South Africa.

Laudin GE ，Lakha AB ，Dullabh N ，Mohanlal R ，Jassat R ，Waja MF ，Philip V ... -  《-》

Rosai-Dorfman Disease Harboring an Activating KRAS K117N Missense Mutation.

Shanmugam V ，Margolskee E ，Kluk M ，Giorgadze T ，Orazi A ... -  《-》

KRAS 117N positive Rosai-Dorfman disease with atypical features.

Rosai-Dorfman disease (RDD), also known as sinus histiocytosis with massive lymphadenopathy, is a rare disease typically characterized by a histiocytic proliferation within lymph nodes, which is due to an unknown etiology. Extranodal involvement can occur, and it more rarely can involve the skin. RDD generally presents with an indolent nature and follows a benign disease course, although more aggressive cases have been reported. The condition predominately affects children and young adults. It is classically characterized by massive, bilateral painless lymphadenopathy and accumulation of CD68-positive, S100-positive, CD1a-negative histiocytes, with the presence of emperipolesis as a hallmark. Herein, we present an aggressive case in a 76-year-old male with past medical history significant for prostate cancer, who presented with a 7-month history of lymphadenopathy and new onset of multiple large abdominal wall, cutaneous, lymph node, liver, and lung masses, all of which were histopathologically atypical, but showed features consistent with RDD, including emperipolesis and strong S100 positivity. Molecular studies showed a KRAS 117N mutation, which has been recently reported in RDD. While most cases present as a benign tumor, this case demonstrated aggressive features clinically, showed partial response to MEK inhibitor immunotherapy in the setting of a KRAS mutation, and demonstrated atypical cytologic features on histopathology.

Jafri ZA ，Reddy SP ，Cassarino DS 《-》