Histiocytic and follicular dendritic cell sarcoma: Diagnostically challenging rare entities

Follicular dendritic cell sarcomas (FDCSs) and histiocytic sarcomas (HSs) are exceedingly rare tumors. Most of the data on those entities are based on case reports or small case series. The natural history and response to different treatment modalities have not been well established.

To analyze the clinicopathologic features, immunophenotypic profile, treatment responses and to add to the existing data on FDCS and HS.

Retrospective descriptive study.

The study was conducted at the department of Oncopathology at a tertiary care cancer hospital in India, retrospectively within the time period of four years (2016-2019). Total eight (8) cases were diagnosed: four cases of FDCS and four cases of HS involving nodal and extra-nodal sites. Clinical, histopathological, immunohistochemistry (IHC) and therapeutic data of the eight cases were retrieved and analyzed.

Descriptive statistics.

Among the four patients of FDCS, two had nodal and two had extra-nodal disease. Mean tumor size was 6 cm. Tumor cells expressed CD23, CD21, CD45, CD68 and S100. One patient received adjuvant chemotherapy (Gemcitabine and Docetaxel). Median survival was 36 months. None of them developed distant metastasis. Two of the patients having HS, developed bone metastasis. Median survival was 8.5 months. CD68 was consistently expressed in all cases of HS. Other applied IHC markers were negative in all the eight cases.

FDCS and HS are under-recognized and easily prone to a wrong diagnosis. Therefore, considering these rare entities in differential diagnoses and inclusion of proper IHC biomarkers are necessary to avoid potential misdiagnosis.