[Interdigitating dendritic cell sarcoma of lower extremities resistant to high dose chemotherapy BEAM with peripheral blood stem cell transplantation].

Interdigitating dendritic cell sarcoma is a rare neoplasm forming part of the group of malignancies derived from histocytic cell line. This nosological unit can be detected only by special immunohistochemical exams. A young man aged 25 found a tumorous swelling in the proximal part of his left crus. The pathological process affected proximal tibial epiphysis and adjacent soft tissues. The first FDG-PET examination performed in the process of determining the clinical stage of the disease showed a high activity in the site of primary tumour (SUV 7.71) and in the site of regional inguinal node (SUV 4.25). Histological examination of a diagnostic excision specimen of the tumour in the tibia and the extirpated enlarged regional nodes in the left groin led to the diagnosis of interdigitating dendritic cell sarcoma. The diagnosis was confirmed pathologically by another two centres in the Czech Republic and, due to the unusual nature of the diagnosis, also in Regensburg, Germany. Treatment started with chemotherapy, applied to patients with aggressive lymphomas in the framework of clinical studies, i.e. a combination of MegaCHOP. After 4 cycles, however, there was no visible response on the site of primary tumour. MegaCHOP therapy was therefore discontinued after the 4 cycles. Subsequently, we referred the patient for a high-dose chemotherapy with autologous bone marrow transplantation, similarly to aggressive lymphomas. The collection of blood producing stem cells from peripheral blood was successfully performed after ESHAP chemotherapy. A verificatoin FDG-PET examination was performed before high-dose chemotherapy. Increased activity was detected only in left proximal crus, with an SUV of 4.6. One month after ESHAP chemotherapy, BEAM high-dose chemotherapy with autologous transplantation of blood forming tissue was performed. High-dose chemotherapy was followed up by radiotherapy targeted on the primary tumour in the crus (70 Gy). The third verification FDG-PET examination was performed 3 months after radiotherapy. The examination showed a continuing higher activity in the region of the primary tumour (SUV 2.69) and a new centre of activity was detected in the left inguinal nodes region (SUV4.09). The activity corresponded to the presence of viable tumour tissue in the primary nidus and new metastases in inguinal nodes, without proofs of further proliferation at the time. Nodes of the left groin were removed. Histological examination showed affection of the node by the same type of tumour, i.e. a continuing activity of the disease despite chemotherapy. Due to suspected continuation of viable tumour in the crus judging by the intensity of accumulation of FDG-PET and the proof of a new affection of regional nodes, surgical treatment was preferred after the failure of chemotherapy. After the removal of inguinal nodes, left knee joint exarticulation was performed. This was followed by regional inguinal node region radiotherapy (56 Gy). The last fourth PET-CT examination carried out 4 months after the radiation therapy of the inguinal region showed massive dissemination into the region ofileac and paraaortic nodes (lymphadenopathy up to 6 cm in diameter) with an activity of 5.9 to 6.73 SUV units. Currently, we test the sensitiveness of the disease to 2-chlordeoxyadenosin and look for additional therapeutic options. To our knowledge, the above description is the first documented case of interdigitating dendritic cell sarcoma located in the tibia and crus soft tissue. We have not found any description of high-dose therapy supported by autologous transplantation of blood-forming tissue for this type of tumour in relevant literature. In this case, we record chemoresistance to high-dose chemotherapy and certain radiosensitivty of the tumour at the same time.