Clinicopathological characteristics of mediastinal follicular dendritic cell sarcoma: report of three cases.

Background: Follicular dendritic cell sarcoma (FDCS) is a rare malignant neoplasm of follicular dendritic cells that form a tight meshwork within lymphoid follicles. It occurs most commonly in the lymph nodes and occasionally at extranodal sites, but rarely in the mediastinum. It is an under-recognized clinical entity without clear diagnosis. Due to its rarity, FDCS is easily misdiagnosed by clinicians or pathologists.

Case Presentation: Herein, we report three unusual cases of mediastinal FDCS, including one with hyaline vascular Castleman's disease in woman. The clinicopathological characteristics and CT imagings were described. Their diagnosis was confirmed by immunohistochemical stainings of specific markers. Their therapeutic intervention, follow-up and outcomes were presented with brief literature review.

Conclusions: A huge mediastinal shallowly-lobulated, demarcated soft tissue mass, with speckled, strip-like, coarse or arborizing calcification inside, and mild to moderate enhancement after contrast material administration on CT image, should consider FDCS as a possible diagnosis.