EBV+ Inflammatory Pseudotumor-like Follicular/Fibroblastic Dendritic Cell Sarcoma: An Uncommon and Challenging Tumor

Abstract

Abstract Casestudy: Inflammatory pseudotumor-like follicular/fibroblastic dendritic cell sarcoma (IP-L FDC/FRC) is a rare dendritic cell neoplasm recognized as a specific entity in the WHO classification of tumors of the hematopoietic and lymphoid tissues. The tumor has specific clinical features, including a predominance in young to middle-aged women typically involving the liver or spleen, with neoplastic cells typically positive for Epstein-Barr virus. Morphologically, the tumor poses a diagnostic challenge to distinguish it from inflammatory pseudotumor and inflammatory myofibroblastic tumor, with which it shares considerable morphologic and immunohistochemical overlap. We present a case report of a 35-year-old female who presented with weight loss, malaise, and intraabdominal mass. MRI revealed a 14 cm large ovoid solid mass with central hemorrhage and necrosis. Biopsy and subsequent resection of the tumor confirmed IP-L FDC/FRC sarcoma. Histologically, the tumor was composed of spindle cells admixed with many lymphocytes and prominent plasma cells. Immunohistochemical stains showed neoplastic spindle cells focally positive for dendritic cell markers CD21, CD23, and CD35, diffuse positivity for SMA, and striking in situ hybridization for Epstein-Barr virus (EBER). Due to its rarity, biologic behavior and outcomes are not well established. The tumors are generally regarded as indolent with a risk of repeated intraabdominal recurrence, although recurrences may be related to the ease and completeness of surgical resection. It is essential to distinguish this tumor from other high- grade sarcomas with greater metastatic potential and overall worse prognosis.