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A4154 - Histiocytic Sarcoma of Interdigitating Reticular Cells in the Mediastinum - Case Report
Author Block: J. M. Lopez, A. Miotto, P. A. A. Honda, J. H. Rivaben, D. C. Dias, R. H. Roja, T. B. Hassegawa, M. Botter, M. C. Braz; Hospital Sancta Maggiore, Sao Paulo, Brazil.
Reticular dendritic cells are present in the germinal center of lymph nodes, with the function of pathogens phagocytation. They present antigens to B and T lymphocytes, acting in the cellular memory. Histiocytic sarcoma is a rare malignant neoplasm with proliferation of cells with morphological and immunophenotypic characteristics of mature histiocytes derived from dendritic cells. In the mediastinum, histiocytic sarcoma of interdigitating reticular cells (HSIRC) are very infrequent, with only 2 reports in the literature. The report is about a male patient, 69 years old, in schedule of radical prostatectomy. In his oncologic staging, chest tomography demonstrated a mediastinal tumor suggestive of lymphnode enlargement in the right paratracheal chain, of 2.8cm. The abdomen examination showed no signs of advanced disease or other lymphadenomegaly. The patient was submitted to resection of the mediastinal lesion, which showed, in histological analysis, a highly pigmented, slightly differentiated fusiform neoplasm and bands of fibrous tissue, without necrosis and with slight atypia. The immunohistochemical panel showed no specific markers of histogenesis. Thus, a diagnosis of HSIRC was made, excluding, by immunohistochemical analysis, the diagnosis of metastasis of prostate neoplasm or other tumors. Surgical resection was the only therapeutic modality performed, currently it is under ambulatory follow-up, with no signs of recurrence. HSIRC is extremely rare in mediastinal localization. It is irregularly distributed in all ages, but with two main peaks of incidence: one from 0 to 29 years and the other from 50 to 69 years. The clinical findings described are non-specific, with symptoms including fatigue, low fever, weight loss and the rising of small and numerous skin lesions. It is a type of neoplasm of low grade of malignancy, but with tendency of recurrence. More aggressive behavior has been reported in tumors of intracavitary location, when already advanced and bulky, with higher mitotic rate and cellular necrosis. The greatest difficulty reported in this type of sarcoma is its differential diagnosis. Most patients are asymptomatic or have nonspecific symptoms, and imaging is the main diagnostic tool. Current treatment protocols suggest optimal treatment as surgery alone, without radiotherapy or chemotherapy. However, a few studies described in the literature are not enough to guide unequivocally the treatment of these neoplasms. The outpatient clinic for about 6 months after surgery had no signs of recurrence.In conclusion, this is an extremely rare disease, poorly described in the literature, and should be included among the differential diagnoses of mediastinal lesions.