Abstract:

Histiocytic sarcoma is a neoplasm of hematopoietic origin characterized by proliferation of malignant cells with morphological and immunohistochemical characteristics of mature macrophages. Prior to development of antibodies for diagnostic immunohistochemistry, many aggressive lymphomas with abundant cytoplasm were mistakenly classified as histiocytic sarcoma. Bona fide histiocytic sarcoma is very rare, representing less than 1% of all non-Hodgkin lymphomas. Herein, we present a 52-year-old female with a 7.6 cm fungating right elbow mass with infiltrating margins. Biopsy showed diffuse sheets of large dyscohesive cells with moderate eosinophilic cytoplasm, irregular nuclei with vesicular chromatin, distinct nucleoli and scattered atypical mitotic figures. By immunohistochemistry, CD163 and CD68 were strongly positive and CD45 was weakly expressed. S100 immunostain highlighted a subset of cells. Pan-cytokeratin, EMA, CD34, SOX10 and all remaining B and T-cell markers were negative. Molecular studies were positive for MLL2 and negative for BRAF V600E mutations. Based on the morphologic features and extensive ancillary data, a diagnosis of histiocytic sarcoma was made. Few months later, the lesion recurred at the same site and the patient underwent resection in conjunction with radiation and neoadjuvant chemoradiation with mesna, ifosfamide and dacarbazine. The lesion subsequently metastasized to the right axillary lymph nodes, vertebral bodies, bone marrow and bilateral lungs. Despite multiple cycles of chemotherapy, the patient died approximately 48 months after diagnosis. Our case illustrates the aggressive clinical course and short survival characteristic of histiocytic sarcoma. Accurate diagnosis through the use of improved diagnostic modalities is essential for advancing our understanding and improving the treatment of this rare neoplasm.

Financial Disclosure:
No current or relevant financial relationships exist.

Menu

Ion Prisneac, MD