Follicular Dendritic Cell Sarcoma (FDCS): A Rare and Incurable Disease.
Authors: Soriano Andres O. , Thompson Michael , Romaguera Jorge , Rodriguez Alma , Hagemeister Fredrick B. , Fayad Luis , Admirand Joan H. , Pro Barbara 
Published: October 2019

Abstract
Objectives: To describe the clinical characteristics, pathologic features, immunophenotype, treatment and outcome of patients with FDCS seen at MD Anderson Cancer Center in the past 10 years.
Background: FDCS is grouped in the WHO classification of tumors with the histiocytic and dendritic cell neoplasms, this group also includes histiocytic sarcoma, Langerhans cell tumors and interdigitating dendritic cell tumors. Data on this disease is based on case reports and case series.
Methods: After IRB approval, cases were identified from the files of the lymphoma and pathology departments at MD Anderson Cancer Center from 1995 to 2005.
Results: Fourteen patients were identified. Median age was 48 years old (25–69). Three patients presented with cervical lymphadenopathy, five had abdominal lymphadenopathy, three had mediastinal adenopathy, two had nasopharyngeal disease and one had pleural involvement. Extranodal disease included liver, spleen, pancreas and pleura. Constitutional symptoms were reported in 2 patients. Median performance status was 1 (0–2). Histologically, five cases showed low grade cytology with proliferation of spindled cells, growth patterns included whorled, storiform, fasicular and nodular. Three cases showed low grade features with focal high grade cytology and a diffuse growth pattern. Five cases showed high grade cytology that also included areas of necrosis in 2 cases and a high mitotic rate (>20/10HPF) in one case. CD21, CD23 and CD35 were positive in 83%, 90% and 44% of the cases respectively. Epidermal growth factor receptor (EGFR) was strongly positive in 12/13 cases tested (92%). The case that tested negative had high grade features and high mitotic rate. One patient had coexistent Castleman’s disease. Information on initial treatment was available in 11 patients which included surgery alone in 1 patient, surgery and radiation in 2 patients, surgery and chemotherapy in 1, chemotherapy alone in 3, chemotherapy and radiation in 1, surgery followed by radiation and chemotherapy in 3 patients. The initial chemotherapy regimen was CHOP in 8 patients. Complete remission (CR) was achieved in 7/11 patients (63%), 3 patients had disease progression and 1 had stable disease. Relapse occurred in all the patients who had a CR. Salvage treatment included surgery in 2 patients and chemotherapy in 7 patients (including the 2 patients who progressed on initial treatment). Two patients underwent allogenic hematopoietic stem cell transplantation after salvage therapy. CR was achieved in 5 patients, partial remission in 2, progression in 1 and stable disease in 1. Information on disease status at last follow up was available in 13 patients. Ten patients were alive at a median follow up of 22 months, 3/13 patients (23%) had no evidence of disease and 7/13 patients (53%) were alive with disease.
Conclusions: The pathologic characteristics and immunophenotype found in our series were similar to those previously reported. EGFR was strongly positive in all but one of the cases tested. Consistent with previous reports Castleman’s disease was found in one of the cases. Although most of the patients initially responded to treatment, all of them eventually relapsed, which is in contrast to previously reported relapse rates of 16–36%. A better understanding of the biology of FDCS could guide our efforts in the development of new treatment modalities for this rare disease.