DIFFERENTIAL DIAGNOSIS OF HISTIOCYTIC SARCOMAS AND UNDIFFERENTIATED PLEOMORPHIC SARCOMAS

Differential diagnosis between histiocytic sarcoma and undifferentiated pleomorphic sarcoma represents an underinvestigated topic of histopathological and oncological interest. Both are rare neoplasms with high-grade cytological features that may involve soft tissues, skin, nervous system, and gastrointestinal tract, among other tissues, in adult patients. Their clinical and morphological overlap may go unnoticed, given the sub-specialistic organization currently adopted in most surgical pathology departments. Data comparing the natural history, treatment, and prognosis of the two conditions is lacking. Moreover, while undifferentiated pleomorphic sarcoma is treated according to international guidelines, for histiocytic sarcoma, a standard of care is lacking, and different therapeutic options are described in the literature. In this study, we compared the clinical, histopathological, and genetic features of three groups of patients diagnosed with histiocytic sarcoma, undifferentiated pleomorphic sarcoma, and dedifferentiated liposarcoma (as a control group). To investigate their diagnostic relevance, we employed different and in-depth technologies, including immunophenotyping, high-throughput sequencing, gene expression profiling, and methylome profiling.