Molecular Basis of Langerhans and Non-Langerhans Cell Histiocytic Neoplasms and Castleman Disease

Inclusion Criteria: * Must have histopathologic confirmation of the particular rare hematologic disease. * Diseases that will be considered as rare hematologic diseases for this study will include the following * Langerhans cell histiocytosis (LCH) * Erdhiem Chester disease (ECD) * Rosai-Dorfman disease (RDD) * Miscellaneous histiocytic entities -indeterminate dendritic cell tumor, interdigitating dendritic cell sarcoma, follicular dendritic cell sarcoma, fibroblastic reticular cell tumor * Unicentric Castleman disease * Multicentric Castleman disease including TAFRO * Follicular Dendritic Cell sarcoma (FDCS) * Newly diagnosed treatment naïve patients as well as patients who received prior therapies (e.g. chemotherapy, targeted therapy, surgery, or radiation) will be included. -Tissue specimens collected within the past 5 yearse will be considered acceptable for study inclusion will include the following * Collected as part of the evaluation for diagnostic confirmation * Tissue specimen or extracted DNA (from blood sample) banked in IRB approved tissue repositories and obtained within five years prior to the date of informed consent. -Tissue samples are planned to be collectedfrom previously stored surgical specimens already being stored in pathology lab * Consent to have germline testing performed in parallel to tumor testingg)Patients willing to receive treatmen Exclusion Criteria: * Life expectancy of less than 6months * Patient unwilling to have germline…