Interdigitating Dendritic Cell Sarcoma
Wesley O. Greaves, MD
L. Jeffrey Medeiros, MD
Key Facts
Clinical Issues
Wide age range
Single lymph nodes most commonly involved
Cervical, axillary, or inguinal groups
Slow-growing, asymptomatic mass
Rare cases associated with B- or T-cell lymphomas or leukemias
Microscopic Pathology
Partial or complete replacement of lymph node architecture
Sheets, whorls, nests, or fascicles
Spindle-shaped or epithelioid cells
Cytologic atypia can be mild or prominent
Ancillary Tests
Immunohistochemistry
S100 strongly positive
CD68(+/-), often variable
Vimentin(+), fascin(+), CD45/LCA(+/-), lysozyme(+/-)
Molecular genetics
HUMARA has shown clonality in small subset of cases tested
Antigen receptor genes are usually in germline configuration
No chromosomal translocations
IDC sarcoma in patients with follicular lymphoma carry IgH rearrangements and t(14;18)/IgH-BCL2
Top Differential Diagnoses
Langerhans cell sarcoma
Follicular dendritic cell sarcoma
Histiocytic sarcoma
 Interdigitating dendritic cell sarcoma subtotally replacing lymph node. The neoplasm tends to spare lymphoid follicles. The neoplasm was S100 protein(+). |
 Interdigitating dendritic cell sarcoma involving lymph node. The neoplastic cells are spindled and epithelioid with abundant eosinophilic cytoplasm. A mitotic figure is present  . |
TERMINOLOGY
Abbreviations
Interdigitating dendritic cell (IDC) sarcoma
Synonyms
Interdigitating cell dendritic cell tumor
Interdigitating dendritic reticulum cell sarcoma
Definitions
Neoplastic proliferation of cells with immunophenotypic profile that is similar to normal IDCs
ETIOLOGY/PATHOGENESIS
Postulated Normal Cell Counterpart is IDC
Antigen-presenting cell that is involved in T-cell immunity
Derived from CD34(+) lymphoid/myeloid progenitor cell in bone marrow that homes to lymph node
Normally found in
T-cell regions of lymph node
Periarteriolar lymphoid sheaths
Interfollicular areas of extranodal lymphoid tissue
Concept of “Transdifferentiation”
Rare patients with histiocytic neoplasms also have clonally related B-cell lymphoma
Usually B-cell lymphoma precedes histiocytic neoplasm
Examples in literature include
IDC sarcoma and follicular lymphoma
Histiocytic sarcoma and follicular lymphoma
IDC sarcoma and chronic lymphocytic leukemia/small lymphocytic lymphoma
Histiocytic sarcoma and splenic marginal zone lymphoma
Histiocytic neoplasms associated with follicular lymphoma share
t(14;18)(q32;q21)/BCL2-IgH &/or identical IgH gene rearrangements
Histiocytic tumors and nonfollicular B-cell lymphomas share identical IgH gene rearrangements
These results suggest that B-cell lymphoma can transform to histiocytic phenotype via “transdifferentiation”
Possibly as result of loss of key components of B-cell differentiation
CLINICAL ISSUES
Epidemiology
Incidence
Very rare
Age
Wide age range
Most patients are adults with median age in 6th or 7th decades
Youngest patient reported was 2 years of age
Gender
Male to female ratio: 1.2 to 1
Site
Lymph node
Most commonly a single lymph node is involved
Cervical, axillary, or inguinal lymph node groups most often affected
Extranodal sites can be involved
Wide variety of extranodal sites
Skin and soft tissue most common
Liver and spleen
Gastrointestinal tract, lung, kidney
Bone marrow is involved in < 20% of patients
Presentation
Slow-growing, asymptomatic mass is most common
Systemic symptoms occur in subset of patients
Fever, night sweats, fatigue
Small subset of patients have IDC sarcoma and another hematopoietic neoplasm including
Chronic lymphocytic leukemia/small lymphocytic lymphoma
Mycosis fungoides
Acute lymphoblastic leukemia (mostly of T-cell lineage)
Small subset of patients with IDC sarcoma also have carcinoma
Most common types: Breast, stomach, liver, colon
Treatment
Surgical resection and radiation therapy for patients with localized disease
Currently, there is no established chemotherapy regimen
ABVD (doxorubicin, bleomycin, vincristine, and dacarbazine) and other regimens have been used
Many patients initially respond but relapse, and death is common in this patient subset
