Extranodal Follicular Dendritic Cell Sarcomas and their Oligorecurrences: Lessons Learnt at a Single Tertiary Cancer Referral Centre, India.

Background: Follicular dendritic cell sarcoma (FDCS) is a rare, aggressive malignant neoplasm usually arising in lymph nodes of the head and neck, but it can also occur at extranodal sites (ENFDCS). Due to its rarity, optimal management is not well defined, underscoring the need for further research.

Methods: We conducted a retrospective analysis of patients with histologically confirmed ENFDCS treated in the gastrointestinal oncology unit of a tertiary cancer center. Clinical features, treatments, and outcomes were reviewed.

Results: Fourteen patients (10 males, 4 females; median age 41 years) were included. Primary sites were colon (n = 6), retroperitoneum (n = 3), rectum (n = 2), mesentery (n = 1), liver (n = 1), and pelvis (n = 1). Four tumors (28.6%) were initially misdiagnosed. Final diagnosis was based on morphology and immunohistochemistry for CD21, CD23, and CD35; Epstein-Barr virus testing was not performed. Five patients underwent primary surgery at our center; two patients with metastatic disease at presentation received systemic therapy alone. Among the five primary surgeries, three were preceded by perioperative chemotherapy (n = 1), neoadjuvant chemotherapy (n = 1), or neoadjuvant radiotherapy (n = 1). Seven patients presented with residual or recurrent disease after prior surgery elsewhere; three underwent re-resection following appropriate systemic therapy, and four received only systemic therapy. At a median follow-up of 26 months (range 7-153), median overall survival was not reached, and median disease-free survival was 24 months. Four of five patients primarily operated at our center remained disease free; one recurred at 39 months, was successfully treated with re-resection and systemic therapy, and was alive at 153 months. Of the three patients re-resected at our center, one remained disease free at 17 months, one developed systemic recurrence and eventually received best supportive care at 11 months, and one was disease free until 94 months before being lost to follow-up. Overall, 10 patients were alive, two died of disease progression, and two were lost to follow-up.

Conclusion: ENFDCS is frequently misdiagnosed; surgery is the cornerstone of treatment, and multimodality therapy for recurrences can yield durable survival. Outcomes appear better when patients are managed at specialized oncologic centers, highlighting the importance of early recognition and timely referral.

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