Follicular Lymphoma Staging
Follicular lymphoma is staged using the Ann Arbor classification system, which divides disease into four stages based on anatomic distribution of lymph node involvement relative to the diaphragm, with additional modifiers for extranodal extension (E), splenic involvement (S), and presence/absence of B symptoms. 1
Ann Arbor Staging System
The staging classification defines four distinct stages based on lymph node region involvement 1:
- Stage I: Single lymph node region OR single extralymphatic site (IE) 1
- Stage II: Two or more lymph node regions OR at least one lymph node region plus a localized extralymphatic site (IIE), all on the same side of the diaphragm 1
- Stage III: Lymph node regions or lymphoid structures (thymus, Waldeyer's ring) on both sides of the diaphragm, with optional localized extranodal site (IIIE) or spleen involvement (IIIS) 1
- Stage IV: Diffuse or disseminated extralymphatic organ involvement 1
A/B Symptom Classification
While the provided guidelines mention bulky disease (>6 cm) should be noted when applicable 1, the traditional A/B symptom classification applies to follicular lymphoma staging. Constitutional B symptoms (fever, night sweats, weight loss) are uncommon in follicular lymphoma unless transformation to aggressive lymphoma has occurred 2, 3.
Recommended Staging Work-Up
The ESMO guidelines mandate a comprehensive initial staging evaluation that directly impacts treatment decisions, particularly for the 10-15% of patients presenting with early-stage disease. 1
Essential Imaging Studies
- PET-CT scan: Recommended for routine staging and mandatory to confirm localized stage I/II disease before involved-site radiotherapy 1
- CT scan: Neck, thorax, and abdomen if PET-CT not available 1
Bone Marrow Evaluation
- Bone marrow aspirate and biopsy of sufficient size (at least 20 mm) 1
- Bone marrow involvement is a critical staging component 4
Laboratory Studies
Complete blood count and routine blood chemistry including 1:
- Immunoglobulin levels
- Lactate dehydrogenase (LDH) - prognostic factor in FLIPI scoring 5, 2
- β2-microglobulin (B2M) - component of FLIPI-2 and PRIMA-PI 1
- Uric acid
- Screening for HIV, HBV, and HCV 1
Clinical Pitfalls and Caveats
Thorough staging is particularly critical for the small proportion (10-15%) of patients with apparent early-stage I-II disease, as these patients may be candidates for curative-intent radiotherapy rather than systemic therapy. 1 Inadequate staging can result in inappropriate treatment selection, potentially denying patients curative options or subjecting them to unnecessary systemic therapy.
The Ann Arbor system has recognized limitations in follicular lymphoma, as most patients present with advanced stage III-IV disease, and stage alone does not fully capture prognostic heterogeneity 6. This is why prognostic indices like FLIPI (incorporating age >60 years, hemoglobin <12 g/dL, elevated LDH, stage III/IV, and >4 nodal areas) are used alongside staging for risk stratification 5, 2.