Context: This article provides an overview of the major pathologic manifestations of sinus histiocytosis with massive lymphadenopathy, including patient characteristics and current knowledge about its pathogenesis, with an emphasis on multifocal and extranodal presentation. Sinus histiocytosis with massive lymphadenopathy is a rare, nonneoplastic, idiopathic, proliferative histiocytic disorder; recognition of this disorder is important to avoid misinterpretation and subsequent unnecessary treatment. This is especially true for primary extranodal manifestation of this rare disorder. Although accurate diagnosis of this entity requires a correlation of clinical, radiologic, laboratory, and pathologic studies in most cases, it remains a disorder primarily defined by its histopathologic features and pathologic manifestations, which are key to the diagnosis.
Objective: To summarize the scientific literature, provide a concise review, and emphasize the diagnostic histopathologic features of extranodal sinus histiocytosis with massive lymphadenopathy.
Data sources: A comprehensive literature review was undertaken to summarize the clinical and pathologic features of this disorder.
Conclusions: Sinus histiocytosis with massive lymphadenopathy is characterized by a rare, acquired, nonmalignant proliferation of distinctive histiocytes that present with lymphadenopathy or extranodal disease, primarily in children and young adults. It exhibits a broad range of clinical presentations, thus eliciting a wide differential diagnosis. The diverse clinical manifestations and frequent association with subtle or severe immunologic abnormalities suggest an immune-mediated cause. Additional studies are needed to characterize the interplay between death receptors and cytotoxic mediators and to further elucidate the loss of immune hemostasis that may underlie idiopathic histiocytic proliferations such as this.