Lymphoma & related disorders

Extranodal organ specific lymphoma

Primary follicular lymphoma-testis

Editorial Board Member: Patricia Tsang, M.D., M.B.A.
Deputy Editor-in-Chief: Genevieve M. Crane, M.D., Ph.D.
Mahsa Khanlari, M.D.
Roberto N. Miranda, M.D.

Last author update: 6 July 2020
Last staff update: 23 August 2022

Copyright: 2020-2023,, Inc.

PubMed Search: Testicular follicular lymphoma

Mahsa Khanlari, M.D.
Roberto N. Miranda, M.D.
Page views in 2022: 1,197
Page views in 2023 to date: 571
Cite this page: Khanlari M, Miranda RN. Primary follicular lymphoma-testis. website. Accessed June 4th, 2023.
Definition / general
  • Primary follicular lymphoma of testis (PFLT) in children and adolescents is a subset of extranodal follicular lymphoma (FL)
  • Lymphoma composed of follicle center B cells that arise in testis
  • Follicular lymphoma involving testis as manifestation of systemic disease is excluded
  • Not recognized as specific variant in 2017 World Health Organization classification
Essential features
  • Localized disease limited to the testis
  • Favorable course despite its aggressive histology
  • Systemic relapses are uncommon
ICD coding
  • ICD-O: 9695/3 - Follicular lymphoma
  • ICD-10: C82.90 - Follicular lymphoma, unspecified
  • Primary non-Hodgkin lymphoma (NHL) of testis: 1% of all cases of non-Hodgkin lymphoma
  • Primary follicular lymphoma of testis is rare
  • Limited to single case reports or small case series
  • Most cases series are in children and young adults
  • Less common in adults
    • In adults non-Hodgkin lymphoma of the testis is mostly diffuse large B cell lymphoma (DLBCL)
  • Reference: Am J Surg Pathol 2007;31:1050
  • Testis
Pathophysiology / etiology
Diagrams / tables

Clinical features:
Nodal follicular lymphoma Testicular follicular lymphoma
Age (median) Adults and elder (sixth decade) Children and young adults
Gender (M:F) Men and women Men only
Affected sites Lymph nodes with extranodal spread Testicle and adnexa
Symptoms Generalized lymphadenopathy Painless mass
Stage (Ann Arbor) High (III - IV) in most cases IE

Pathologic features:
Nodal follicular lymphoma Testicular follicular lymphoma
Gross appearance Discrete mass or complete effacement Discrete mass or diffuse involvement
Histologic grade Grades 1 - 3 Grade 3

Nodal follicular lymphoma Testicular follicular lymphoma
CD10 Variable Variable
BCL2 Usually positive Negative

Molecular features:
Nodal follicular lymphoma Testicular follicular lymphoma
IGH-BCL2 Present, up to 90% Negative
Clinical features
  • Painless discrete mass or diffuse testicular enlargement
  • May be mistaken with hydrocele (Cancer 1999;85:1626)
  • No peripheral lymphadenopathy
  • No hepatosplenomegaly
  • No B symptoms
  • Reported cases are predominantly at clinical stage of IE
Radiology description
  • Ultrasonography:
    • Hypoechoic areas
    • Variably hypervascular
Prognostic factors
  • Excellent prognosis for children and young adults with stage IE disease
    • Enrollment in Children’s Oncology Group may be important for developing future advances in treatment
  • Small number of adult cases with generally short follow up
  • Reference: J Pediatr Hematol Oncol 2004;26:104
Case reports
  • Resection
  • With or without subsequent chemotherapy
Gross description
  • Discrete mass or diffuse involvement of testis
  • Fleshy tan or pink distinct nodule
  • Either poorly or well demarcated
  • 1.2 - 4.0 cm
  • Reference: J Pediatr Hematol Oncol 2012;34:68
Frozen section description
  • Same criteria applied in microscopic evaluation
  • When possible, spare tissue for cytogenetic analysis, flow cytometry immunophenotype; preparation of imprints is recommended
Microscopic (histologic) description
  • Nodular pattern consistent with follicular lymphoma
  • Follicular lymphoma involves mainly testicular parenchyma and secondarily adnexa
    • Neoplastic follicles grow between tubuli
    • May completely replace testicular parenchyma
  • Reported cases are predominantly grade 3A
    • Large lymphocytes (centroblasts) predominate
    • Some small cleaved lymphocytes (centrocytes) are admixed
  • Occasionally, focal areas of diffuse growth support focal diffuse large B cell lymphoma
  • Prominent interstitial fibrosis (Am J Surg Pathol 2007;31:1050)
  • Mantle zone usually attenuated or lost around neoplastic follicles
Microscopic (histologic) images

Contributed by Roberto N. Miranda, M.D.

Follicular lymphoma of testis

Seminiferous tubuli and neoplastic follicle

Large centroblasts of follicular lymphoma



DLBCL of testis

Cytology description
  • Majority of cells: large noncleaved cells (centroblasts)
  • Multilobated large cells
  • May be an admixture of centroblasts and small centrocytes
  • Reference: Hum Pathol 2012;43:1514
Positive stains
  • Pan-B cell antigens
  • Monotypic surface Ig
  • CD10 (variable) and BCL6 protein (variable)
    • Weakly expressed by cells in the interfollicular region
  • Ki67 / MIB1: high proliferation rate
  • p53 protein: often positive in primary follicular lymphoma of testis of adults
  • Reference: Arch Pathol Lab Med 2001;125:428
Negative stains
Molecular / cytogenetics description
  • Monoclonal IGH rearrangements
  • IGH-BCL2 fusion is uncommon based on PCR and FISH
  • With or without BCL6 translocations (Cancer 1999;85:1626)
Sample pathology report
  • Right testicular tumor, orchiectomy:
    • Follicular lymphoma with a follicular pattern, grade 3A, with prominent sclerosis (see comment)
    • Comment: Histologic sections demonstrate testicular parenchyma almost completely involved by malignant lymphoma. The lymphoma consists of numerous neoplastic follicles, that are composed of large noncleaved cells (centroblasts) that average > 15 per high power field, admixed with small cleaved lymphocytes (centrocytes) supporting a diagnosis of follicular lymphoma grade 3A. The neoplastic cells surround and invade seminiferous tubulei displacing germ cells and Sertoli cells. Tumor cells inside of the seminiferous tubulei are also seen. Mitoses are easily found. Small areas of infarction are seen in the testicular parenchyma. The noninvolved testicular parenchyma is morphologically unremarkable.
  • Immunophenotypic studies show that the tumor cells are positive for CD10, CD20, CD45 (LCA) and BCL6 (less than 10%). The aberrant cells are negative for CD3, CD5, MUM1 and BCL2. CD21 highlights residual follicular dendritic cell networks in a subset of the neoplastic follicles. The proliferation index as determined by Ki67 is approximately 60%.
  • Fluorescence in situ hybridization (FISH) performed in the laboratory of cytogenetics did not detect rearrangement of the MYC gene. However, extra copies of the MYC gene consistent with an aneuploid cell population were detected.
  • FISH studies failed to detect the presence of of t(14;18) or IGH-BCL2 fusion.
Differential diagnosis
  • Diffuse large B cell lymphoma (DLBCL):
    • Diffuse large B cell lymphoma is most common lymphoma involving testis
      • Primary follicular lymphoma of testis can be grade 3 and predominantly diffuse
    • Features supporting diffuse large B cell lymphoma over extranodal follicular lymphoma
      • Evidence of other disease sites in patients with systemic diffuse large B cell lymphoma
      • No areas of follicular pattern in primary diffuse large B cell lymphoma of testis
      • Diffuse large B cell lymphoma often CD10-, BCL6-
  • Reactive follicular hyperplasia:
    • Follicles show polarization
    • Surrounded by distinct mantle zones
    • Follicles have polymorphic appearance
    • Tingible body macrophages
    • B cell antigens+, CD10+, BCL6+, BCL2-
    • No evidence of monoclonal IGH rearrangements
Board review style question #1
Which of the following extranodal follicular lymphomas is predominantly high grade?

  1. Ocular adnexa
  2. Small intestine
  3. Stomach
  4. Testis
Board review style answer #1
Board review style question #2

A 26 year old man has presented with a testicular mass without any previous history of infection or autoimmune disease. Monoclonal IGH rearrangement is detected on the fresh tissue submitted at the time of excision. Which of the following options is most likely correct about this patient or patient's pathology sample?

  1. IGH-BCL2 rearrangement is detected in cytogenetic studies
  2. Lymphoma has high grade feature
  3. Patient has generalized lymphadenopathy
  4. Patient's prognosis is poor despite therapy
Board review style answer #2
B. Lymphoma has high grade feature

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Reference: Testicular follicular lymphoma
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