Diagnosis and Prognosis

Diagnosing follicular lymphoma (FL)

  • Diagnosis is primarily based on a combination of laboratory, radiologic, and pathologic evaluations1,2
    • Patients with FL typically present with superficial lymph nodes of small to medium size, which sometimes go unnoticed by the patient3
      • Primary mediastinal involvement is uncommon3
      • Patients may present with B symptoms or symptoms from the slow growth of lymphoma in deep areas of the body such as the infradiaphragmatic territories3
      • 50% to 60% of cases have bone marrow involvement3
    • Essential laboratory workup parameters include a complete blood count, serum lactate dehydrogenase (LDH) levels, and beta-2-microglobulin (B2M) levels1,2
    • Initial radiologic imaging studies should include positron emission tomography–computed tomography (PET–CT)4
  • Pathologic testing includes morphologic evaluation and immunophenotyping2
    • Excisional diagnostic biopsy is critical to avoid false-negative results and inaccurate histologic classification1
    • When a lymph node is not easily accessible for excisional or incisional biopsy, a combination of core biopsy and fine-needle aspiration (FNA) biopsies in conjunction with ancillary techniques such as immunohistochemistry (IHC), flow cytometry, polymerase chain reaction (PCR), and fluorescence in situ hybridization (FISH) may be sufficient for diagnosis2
    • FNA or core needle biopsy alone is generally not suitable for the initial diagnosis of lymphoma1,2
  • Two methods used for immunophenotyping are paraffin section IHC and cell surface marker analysis by flow cytometry2 (Table 1)
  • In addition, techniques to assess the cytogenetics of the lymphoma cells may be helpful in determining whether a genetic rearrangement, such as a chromosomal translocation t(14;18) involving the BCL-2 gene, has occurred2

Table 1. Characterizing immunophenotypes in FL in a heterogeneous population. These assays should be used with other diagnostic tools2,5-9

Immunohistochemistry panel for FL for analysis of paraffin section

  CD20 CD10 CD5 BCL-2 Cyclin D1 CD3 CD23 CD21 BCL-6
Antigen + + + –/+ +/– –/+ +
Flow cytometry panel for FL
  Kappa/lambda CD19 CD20 CD5 CD23 CD10  
  +/– +/– + –/+ +    

+/– = >50%, –/+ = <50%.

Staging and grading follicular lymphoma (FL)

  • The staging of FL is based on the Lugano modification of the Ann Arbor staging classification (Table 2)4
    • The classification is based primarily on the distribution of lymphatic involvement with respect to the diaphragm and the presence of extralymphatic organ involvement4
  • In the revised staging system, extent of disease is determined by position emission tomography–computed tomography for avid lymphomas such as FL and by computed tomography for nonavid histologies4

Table 2. A revised staging system based on the Ann Arbor system is recommended to assess nodal and extranodal regions4



Extranodal (E) Status

I One node* of a group of adjacent nodes Single extranodal lesions without nodal involvement
II Two or more nodal groups on the same side of the diaphragm Stage I or II by nodal extent with limited contiguous extranodal involvement
II bulky II as above with “bulky” disease Not applicable
III Nodes on both sides of the diaphragm; nodes above the diaphragm with spleen involvement Not applicable
IV Additional noncontiguous extralymphatic involvement Not applicable

*Tonsils, Waldeyer’s ring, and spleen are considered nodal tissue.4
Whether Stage II bulky disease is treated as limited or advanced disease may be determined by histology and a number of prognostic factors.4

WHO classification of histological grades

  • Use of a grading system divides patients into subgroups and influences both the timing of therapy as well as treatment decisions10,11
  • The WHO classification of FL mentions that grading can be carried out according to the counting method proposed by Mann and Berard to define 3 grades10 (Table 3)
    • This system describes 3 grades (Grades 1 to 3) based on the absolute number of centroblasts (large or small) per 40x high-power field10
    • The vast majority (80% to 90%) of FLs are Grades 1 to 210
    • A classification of FL Grade 3 suggests that the patient is at high risk for disease progression10
      • FL Grade 3 is divided into Grades 3A and 3B based on the presence of centrocytes10
      • FL Grade 3 is commonly treated according to NCCN diffuse large B-cell lymphoma (DLBCL) treatment guidelines.2,12 For more information, please refer to the transformed FL section under DLBCL

Table 3. WHO classification of histological grades10

WHO classification of histological grades



1-2 (low grade) 0-15 centroblasts per hpf
1 0-5 centroblasts per hpf
2 6-15 centroblasts per hpf
3 >15 centroblasts per hpf
3A Centrocytes present
3B Solid sheets of centroblasts
Reporting of pattern Proportion follicular
Follicular >75%
Follicular and diffuse 25%-75%*
Focally follicular <25%*
Diffuse 0%
Diffuse areas containing >15 centroblasts per hpf are reported as DLBCL with follicular lymphoma (Grades 1 to 2, Grade 3A, or Grade 3B).*

hpf, high power field of 0.159 mm2 (40 x objective, 18 mm field of view ocular, count 10 hpf and divide by 10).
If using a 20 mm field of view ocular, count 8 hpf and divide by 10 or count 10 hpf and divide by 12 to get the number of centroblasts/0.159 mm2 hpf.
If using a 22 mm field of view ocular, count 7 hpf and divide by 10 or count 10 hpf and divide by 15 to get the number of centroblasts/0.159 mm2 hpf.
*Give approximate percentage of each in report.
If the biopsy specimen is small, a note should be added that the absence of follicles may reflect sampling error.

Prognostic Indicators

Follicular Lymphoma International Prognostic Index (FLIPI)

  • The FLIPI was proposed and validated in an international cooperative study published in 200413
  • FLIPI predicts the outcome and relative risk of death through 5 adverse prognostic risk factors and stratifies patients into 3 risk groups13 (Tables 4 and 5)

Table 4. Follicular Lymphoma International Prognostic Index (FLIPI) risk factors13

FLIPI risk factors

(1) Age >60 years
(2) Ann Arbor Stage III/IV
(3) Hemoglobin level <12 g/dL
(4) LDH level >ULN
(5) Number of nodal areas >4

Table 5. Follicular Lymphoma International Prognostic Index (FLIPI) by risk group13

FLIPI by risk group

Risk group

Number of risk factors

Percentage of patients

5-year OS rate

10-year OS rate

Low 0-1 36% 91% 71%
Intermediate 2 37% 78% 51%
High ≥3 27% 53% 36%
  • This widely accepted prognostic index is based on a retrospective analysis of more than 4000 patients diagnosed with FL between 1985 and 199213
    • The analysis showed that patients falling into the low-risk group had a median 10-year overall survival (OS) rate of 71% vs 36% for patients falling into the high-risk group13 (Table 5)
    • The FLIPI may be used in determining patient prognosis, but it has not been established as a means of selecting treatment options outside of the clinical trial setting2

Figure 1. Overall survival of FL patients by FLIPI risk group13

Overall survival of FL patients by FLIPI risk group


  • Because FLIPI was based on a retrospective analysis that was formulated before the widespread use of chemoimmunotherapy, the prospective F2 trial (N=1093) was designed and conducted14
  • In the F2 trial, PFS was the primary endpoint instead of OS due to the lengthy course of the disease14
  • Following analysis of the F2 trial:
    • 3 prognostic risk factors were removed14 (Table 6)
      • Ann Arbor Stage III/IV
      • Number of nodal areas >4
      • LDH level >upper limit of normal (ULN)
    • 3 prognostic risk factors were added14 (Table 6)
      • Longest diameter of the largest involved node (LoDLIN) >6 cm
      • Serum B2M >ULN
      • Bone marrow involvement
  • The analysis showed that patients in the low-risk group had a 5-year PFS rate of 80% vs 19% for patients in the high-risk group14 (Table 7)

Table 6. The 5 revised adverse prognostic risk factors for the FLIPI214

FLIPI2 risk factors

(1) Age >60 years
(2) Hemoglobin level <12 g/dL
(3) Serum B2M >ULN
(4) LoDLIN >6 cm
(5) Bone marrow involvement

Table 7. FLIPI2 by risk group14

FLIPI2 by risk group

Risk group

Number of risk factors

Percentage of patients

3-year PFS rate

5-year PFS rate

Low 0 20% 91% 80%
Intermediate 1-2 53% 69% 51%
High 3-5 27% 51% 19%
  • The relatively small size of the F2 trial has resulted in a slow uptake of this prognostic tool. However, current studies have shown that the FLIPI2 is a reproducible prognostic index of clinical utility for the initial prognostic assessment of patients with follicular lymphoma (FL)15

Gene expression profiling (GEP) and prognosis

GEP correlates gene expressions with diagnostic characteristics, progression, response to therapy, and transformation in FL.16

  • Genes associated with infiltrating immune cells in the tumor predict clinical behavior and treatment response16
  • Genes involved in apoptosis, proliferation, and metastasis predict the course of the disease and patient outcome16


  1. Dreyling M, Ghielmini M, Marcus R, Vitolo U, Ladetto M, for the ESMO Guidelines Working Group. Newly diagnosed and relapsed follicular lymphoma: ESMO clinical practice guidelines for diagnosis, treatment and follow-up. Ann Oncol. 2014;25(suppl 3):iii76-iii82. doi:10.1093/annonc/mdu200. PMID: 25122695
  2. Referenced with permission from the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®) for B-cell Lymphomas. V.4.2018. © National Comprehensive Cancer Network, Inc. 2018. All rights reserved. Published May 15, 2018. Accessed June 4, 2018. To view the most recent and complete version of the guidelines, go online to www.nccn.org. NATIONAL COMPREHENSIVE CANCER NETWORK®, NCCN®, NCCN GUIDELINES®, and all other NCCN Content are trademarks owned by the National Comprehensive Cancer Network, Inc.
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  7. Shiozawa E, Yamochi-Onizuka T, Yamochi T, et al. Disappearance of CD21-positive follicular dendritic cells preceding the transformation of follicular lymphoma: immunohistological study of the transformation using CD21, p53, Ki-67, and P-glycoprotein. Pathol Res Pract. 2003;199:293-302. PMID: 12908519
  8. Weiss LM, Loera S, Bacchi CE. Immunoglobulin light chain immunohistochemistry revisited, with emphasis on reactive follicular hyperplasia versus follicular lymphoma. Appl Immunohistochem Mol Morphol. 2010;18:199-205. PMID: 20042853
  9. Mantei K, Wood BL. Flow cytometric evaluation of CD38 expression assists in distinguishing follicular hyperplasia from follicular lymphoma. Cytometry B Clin Cytom. 2009;76:315-320. PMID: 19382196
  10. Harris NL, Swerdlow SH, Jaffe ES, et al. Follicular lymphoma. In: Swerdlow SH, Campo E, Harris NL, et al, eds. WHO classification of tumours of hematopoietic and lymphoma tissues. 4th ed. Lyon, France: International Agency for Research on Cancer; 2008:158-166.
  11. Czuczman MS. Controversies in follicular lymphoma: "who, what, when, where, and why?" (not necessarily in that order!). Hematology Am Soc Hematol Educ Program. 2006:303-310. PMID: 17124076
  12. Freedman AS, Friedberg JW, Mauch PM, Dalla-Favera R, Harris NL. Follicular lymphoma. In: Armitage JO, Mauch PM, Harris NL, Coiffier B, Dalla-Favera R, eds. Non-Hodgkin Lymphomas. 2nd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2010:266-283.
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  15. Arcaini L, Merli M, Passamonti F, et al. Validation of follicular lymphoma international prognostic index 2 (FLIPI2) score in an independent series of follicular lymphoma patients. Br J Haematol. 2010;149:455-457. PMID: 20064149
  16. Rimsza LM, Jaramillo MC. Indolent lymphoma: follicular lymphoma and the microenvironment—insights from gene expression profiling. Hematology Am Soc Hematol Educ Program. 2014:163-168. PMID: 25696850