Follicular dendritic cell sarcoma of the tonsil: case report and review of literature.

OBJECTIVE

To explore the clinicopathologic features, immunophenotype, differential diagnosis, and prognosis of tonsil follicular dendritic cell sarcoma (FDCS).

METHODS

In the Department of Pathology, the affiliated Yantai Yuhuangding Hospital of Qingdao University, in 2019, a case of tonsil FDCS was diagnosed and retrospectively analyzed to summarize its clinical and pathologic characteristics. Relevant literature was reviewed.

RESULTS

The patient was a 71-year-old man. The tumor occurred in the right tonsil with a maximum diameter of 3.5 cm. Microscopically, the tumor cells were spindle-shaped or oval-shaped, arranged in bundles or swirls, and some areas formed concentric circles around blood vessels. Small lymphocytes were distributed in the background. The nucleus was oval-shaped or round, with nuclear chromatin and small central nucleoli. Mitoses were up to 5/10 HPF at the highest. Immunohistochemistry showed positive expression of CD21, CD23, CD68, vimentin, and D2-40 in tumor cells, and Ki67 proliferation index was about 20%. CXCL13 was positive only in scattered background lymphocytes. In situ hybridization for EBER was negative. After surgical resection of the tumor, without radiotherapy or chemotherapy, the patient has been followed up for 4 months until now, without recurrence or metastasis.

CONCLUSION

FDCS is a rare tumor, especially in extranodal sites. The pathogenesis, treatment and prognosis of FDCS still need further exploration.