Diagnostic Challenges in Primary Pulmonary Follicular Dendritic Cell Sarcoma: Two Case Reports
Overview
Primary pulmonary follicular dendritic cell sarcoma (FDCS) is a rare malignant tumor often misdiagnosed due to its uncommon location and histological overlap with lung cancer. This report analyzes two cases, highlighting their clinicopathological features, immunophenotype, and outcomes, alongside a literature review of 11 additional cases.
Background
Follicular dendritic cell sarcoma is a malignant neoplasm arising from follicular dendritic cells, typically found in lymph nodes but occasionally presenting extranodally. Primary pulmonary FDCS is extremely rare and can be mistaken for lung carcinoma on biopsy. Accurate diagnosis relies on recognizing characteristic histological patterns and immunohistochemical markers specific to follicular dendritic cells. Understanding these features is essential to avoid misdiagnosis and guide appropriate management.
Data Highlights
Characteristic
Number of Cases (n=13)
Male patients
10
Female patients
3
Median age (years)
51 (range 33–76)
Main symptom
Coughing
Deaths due to FDCS
2
No recurrence observed
11
Ki-67 proliferation index range
35%–60%
Key Findings
Primary pulmonary FDCS presents as solitary lung masses without lymphadenopathy or distant metastases at diagnosis.
Histologically, tumor cells show ovoid or spindle morphology with diffuse, fascicular, or swirling patterns and abundant lymphocytic infiltration.
Immunohistochemistry reveals positivity for follicular dendritic cell markers CD21, CD23, CD35, fascin, and vimentin; variable expression of podoplanin (D2-40) and SMA; and negativity for epithelial markers CK and P40 in most cases.
EBV-encoded RNA in situ hybridization is negative, excluding EBV association in these pulmonary FDCS cases.
Patients treated with surgery and adjuvant chemotherapy showed favorable outcomes with no recurrence or metastasis during follow-up periods of 14 and 15 months.
Review of 13 cases indicates a male predominance and relatively favorable prognosis despite the tumor’s rarity and diagnostic challenges.
Clinical Implications
Clinicians and pathologists should consider primary pulmonary FDCS in the differential diagnosis of lung masses, especially when biopsy specimens show spindle or ovoid cells with lymphocytic background. Utilization of a panel of follicular dendritic cell markers is critical to avoid misdiagnosis as lung carcinoma. Early and accurate diagnosis enables appropriate surgical and adjuvant treatment, which is associated with favorable patient outcomes.
Conclusion
Primary pulmonary FDCS is a rare malignancy that poses diagnostic challenges due to its uncommon site and histological overlap with other lung tumors. Awareness of its clinicopathological features and immunophenotype facilitates accurate diagnosis and effective management, improving prognosis.
Related Resources & Content
Monda et al. 1986 -- First report of follicular dendritic cell sarcoma
