Co-expression of multiple cytokines and their receptors in primary clear cell sarcoma of the pubic bone with features of a small round cell tumor.

We present the case of an 81-year-old man with primary clear cell sarcoma (CCS) of the pubic bone with an associated aggressive clinical course. The patient's laboratory tests showed marked leukocytosis, elevated levels of C-reactive protein and multiple cytokines, including interleukin-6 (IL-6) and granulocyte colony-stimulating factor (G-CSF). Histological examination showed monomorphic small cells predominantly arranged as a diffuse sheet with morphological features of a small round cell tumor (SRCT). Immunohistochemical staining indicated that the tumor cells were positive for HMB45, S100, Melan A, IL-6, IL-6 receptor, G-CSF, and G-CSF receptor and negative for cytokeratin (AE1/AE3) and epithelial membrane antigen. To the best of our knowledge, this is the first case report of aggressive primary CCS of the pubic bone with features of SRCT showing the production and co-expression of multiple cytokines and their receptors. Thus, we suggest that proliferation through an IL-6- and G-CSF-associated autocrine mechanism may play an important role in the aggressive clinical course and poor prognosis of some CCSs showing features of SRCT.