Primary Follicular Lymphoma of the Testis and Epididymis in Adults

Diagnosis and Classification of Follicular Lymphoma and Related Entities

Follicular lymphoma (FL) is a mature B cell neoplasm classically characterized by B cells harboring the t(14;18) IGH::BCL2 leading to the overexpression of BCL2 in most cases. Conventional FL occurs in lymph nodes and typically shows a follicular B-cell proliferation expressing at least one germinal center marker. Two early lesions closely related to conventional FL are recognized as variants, namely in situ follicular neoplasia (ISFN), and duodenal-type follicular lymphoma (DTFL). FL lacking BCL2 rearrangement ( BCL2 -R negative) accounts for around 10% to 15% of FLs and constitutes a heterogeneous group of FLs. Most of these alternative forms of FL are considered as distinct entities separate from conventional FL in the 2022 International Consensus Classification. This review aims to summarize the key pathologic and diagnostic features of FL conventional and its alternative forms as well as further emphasize the increasing role of molecular studies in the diagnostic work-up.

Bridging clinicopathologic features and genetics in follicular lymphoma: Towards enhanced diagnostic accuracy and subtype differentiation

Follicular lymphoma (FL) is a neoplasm that originates from germinal center B cells and typically forms at least a partial follicular pattern. Approximately 85% of FL cases harbor the t(14;18)(q32;q21)/IGH::BCL2 which leads to the overexpression of BCL2. These cases are referred to as classic FL in the current World Health Organization classification [1]. These neoplasms often exhibit hallmark epigenetic deregulation due to recurrent mutations in genes such as KMT2D, CREBBP, and EZH2, with KMT2D and CREBBP considered founding events in FL lymphomagenesis. In contrast, about 15% of FL cases are negative for the t(14;18), which could present diagnostic challenges. These cases may lack the typical genetic markers and require careful pathological and molecular analysis for accurate diagnosis. This review aims to provide an up-to-date pathology resource on FL, focusing on the pathological and molecular characteristics of these neoplasms. We will detail the diagnostic criteria for FL and emphasize the importance of genetic and mutational analyses in accurately characterizing and distinguishing FL subtypes. Furthermore, we will propose methodologies and best practices for the diagnostic work-up of FL to enhance diagnostic accuracy.

A rare case of primary testicular follicular lymphoma in a pediatric patient

Testicular follicular lymphoma (TFL) is an exceedingly rare lymphoma that typically occurs in young male patients and is now recognized as a distinct diagnostic entity in the International Consensus Classification. TFL shows some clinicopathologic and genetic overlap with pediatric-type follicular lymphoma (PTFL). We report a case of TFL occurring in an otherwise healthy 4-year-old boy who presented with painless scrotal swelling. Orchiectomy revealed a 1.5-cm left testicular mass. Histologic sections showed a dense lymphoid infiltrate with nodular/follicular architecture growing between the seminiferous tubules. The infiltrate was composed of CD20/PAX5-positive B-cells that coexpressed germinal center markers (CD10, BCL6, MEF2B); they were negative for BCL2. No BCL2 or BCL6 rearrangements and no TNFRSF14 deletion were detected by FISH. Chromosomal microarray analysis detected copy-neutral loss of heterozygosity (CN-LOH) at 1p36.33-p36.32 (region of TNFRSF14). Next-generation sequencing detected variants in GNA13, RHOA, and TNFRSF14. In conclusion, this case shows the classic clinical, pathologic, and genetic features of TFL and highlights the similarities to PTFL and the importance of distinguishing this entity from other subtypes of FL. Patients with TFL typically respond favorably to orchiectomy and chemotherapy and have excellent clinical outcomes.

Adult-Onset Pediatric-Type Follicular Lymphoma of the Parotid Gland

Pediatric-type follicular lymphoma (PTFL) is an extremely rare B-cell lymphoma that primarily affects children and young adults, typically in individuals under 25 years old, with a median age of 15 years. Here, we report a rare case of PTFL in a 27-year-old adult male who presented with a slow-growing mass near his left ear. Initial CT scans of the neck revealed two oval-shaped, smooth, well-defined, homogeneously enhancing soft tissue density lesions in the superficial lobe of the left parotid gland. A complete surgical excision was performed, and a postoperative ultrasound of the neck confirmed complete removal, with only hypoechoic changes observed in the parotid gland. Comprehensive immunohistochemical analysis showed CD20-positive B cells co-expressing germinal center markers CD10 and BCL6 but negative for BCL2 and cyclin D1. The Ki-67 proliferation index was notably elevated, indicating high cellular activity. Additional findings included MEF2B positivity, confirming the lymphoma diagnosis, and an immunoglobulin gene rearrangement, which demonstrated a monoclonal B-cell population consistent with a neoplastic process. CD21 staining further revealed distorted follicular dendritic cell networks and attenuated IgD-positive mantle. Fluorescence in situ hybridization (FISH) analysis showed no rearrangements in BCL2, IRF4, or BCL6, and any deletion in the 1p36 region (TNFRSF14 gene), ruling out other lymphoma types. Histologically, the nodules showed distorted secondary follicles with obscured germinal centers, confirming PTFL. At the three-month follow-up, the patient demonstrated satisfactory healing with no signs of recurrence. This case underscores the importance for oncologists to perform a thorough differential diagnosis of head and neck masses, as PTFL can present with characteristics similar to classical follicular lymphoma, IRF4-rearranged large B-cell lymphoma, pediatric nodal marginal zone lymphoma, and reactive follicular hyperplasia. A comprehensive diagnostic approach, including clinical, pathological, and immunohistochemical analyses, is essential for developing an accurate diagnosis and management plan for PTFL, especially in atypical adult presentations.

Navigating the Heterogeneity of Follicular Lymphoma and its Many Variants: An Updated Approach to Diagnosis and Classification

Follicular lymphoma (FL) is a lymphoid neoplasm composed of follicle center (germinal center) B cells, with varying proportions of centrocytes and centroblasts, that usually has a predominantly follicular architectural pattern. Over the past decade, our understanding of FL has evolved significantly, with new recognition of several recently defined FL variants characterized by distinct clinical presentations, behaviors, genetic alterations, and biology. This manuscript aims to review the heterogeneity of FL and its variants, to provide an updated guide on their diagnosis and classification, and to describe how approaches to the histologic subclassification of classic FL have evolved in current classification schemes.

IGH/BCL2 Status Better Predicts Clinico-Pathological Behavior in Primary Splenic Follicular Lymphoma than Histological Grade and Other Molecular Markers

Splenic lymphoma may be primary or secondary. Primary splenic lymphoma's are rare and usually of follicular cell origin representing <1% of Non-Hodgkin's Lymphoma's. Most are secondary with 35% representing Marginal Cell sub-type with the rest being Diffuse Large B-Cell Lymphoma's. Unlike the uniformly aggressive clinical course of Diffuse Large B-Cell Lymphoma's, biological behavior of Primary Splenic CD10-Positive Small B-Cell Lymphoma/Follicular Lymphoma remains less well defined. We present here a solitary splenic mass confirmed as Primary Splenic CD10-Positive Small B-Cell Lymphoma/Follicular Lymphoma after a diagnostic splenectomy. Biopsy revealed monomorphic small lymphoid cells with low grade mitotic activity. Flow cytometry showed a lambda restricted population of B-Cells displaying dim CD19 and CD10. The cells were negative for CD5, CD11c, and CD103. FISH was negative for IGH/BCL2 fusion unlike nodal Follicular Lymphoma's which are usually positive for this translocation. Evidence from this case and a review of literature support the finding that Primary Splenic CD10-Positive Small B-Cell Lymphoma/Follicular Lymphoma is less likely to have the classic IGH-BCL2 fusion and the associated chromosomal 14;18 translocation. This profile is associated with less aggressive clinical behavior even when histopathology represents a high-grade pattern. In such cases splenectomy alone is adequate for localized disease when negative for IGH/BCL2 fusion regardless of histological grade.

New developments in non-Hodgkin lymphoid malignancies

The revised fourth edition of the World Health Organization (WHO) Classification of Tumours of Haematopoietic and Lymphoid Tissues (2017) reflects significant advances in understanding the biology, genetic basis and behaviour of haematopoietic neoplasms. This review focuses on some of the major changes in B-cell and T-cell non-Hodgkin lymphomas in the 2017 WHO and includes more recent updates. The 2017 WHO saw a shift towards conservatism in the classification of precursor lesions of small B-cell lymphomas such as monoclonal B-cell lymphocytosis, in situ follicular and in situ mantle cell neoplasms. With more widespread use of next generation sequencing (NGS), special entities within follicular lymphoma and mantle cell lymphoma were recognised with recurrent genetic aberrations and unique clinicopathological features. The diagnostic workup of lymphoplasmacytic lymphoma and hairy cell leukaemia has been refined with the discovery of MYD88 L265P and BRAF V600E mutations, respectively, in these entities. Recommendations in the immunohistochemical evaluation of diffuse large B-cell lymphoma include determining cell of origin and expression of MYC and BCL2, so called 'double-expressor' phenotype. EBV-positive large B-cell lymphoma of the elderly has been renamed to recognise its occurrence amongst a wider age group. EBV-positive mucocutaneous ulcer is a newly recognised entity with indolent clinical behaviour that occurs in the setting of immunosuppression. Two lymphomas with recurrent genetic aberrations are newly included provisional entities: Burkitt-like lymphoma with 11q aberration and large B-cell lymphoma with IRF4 rearrangement. Aggressive B-cell lymphomas with MYC, BCL2 and/or BCL6 rearrangements, so called 'double-hit/triple-hit' lymphomas are now a distinct entity. Much progress has been made in understanding intestinal T-cell lymphomas. Enteropathy-associated T-cell lymphoma, type II, is now known to not be associated with coeliac disease and is hence renamed monomorphic epitheliotropic T-cell lymphoma. An indolent clonal T-cell lymphoproliferative disorder of the GI tract is a newly included provisional entity. Angioimmunoblastic T-cell lymphoma and nodal T-cell lymphomas with T-follicular helper phenotype are included in a single broad category, emphasising their shared genetic and phenotypic features. Anaplastic large cell lymphoma, ALK- is upgraded to a definitive entity with subsets carrying recurrent rearrangements in DUSP22 or TP63. Breast implant-associated anaplastic large cell lymphoma is a new provisional entity with indolent behaviour. Finally, cutaneous T-cell proliferations include a new provisional entity, primary cutaneous acral CD8-positive T-cell lymphoma, and reclassification of primary small/medium CD4-positive T-cell lymphoma as lymphoproliferative disorder.

Scientific Advances and the Evolution of Diagnosis, Subclassification and Treatment of Lymphoma

The diagnosis of lymphoma has evolved tremendously over time. Initially, diagnosis of lymphoma was largely based on morphology alone. Over time, immunophenotyping using flow cytometry and immunohistochemistry, and then in situ hybridization, have contributed dramatically to the pathologist's ability to recognize, diagnose and subclassify lymphomas more precisely. In recent years, cytogenetic and molecular genetic techniques have developed that allow evaluation of abnormalities in lymphomas, leading to an understanding of their pathogenesis and opening the door to targeted therapies that will lead to better outcomes for lymphoma patients.

The broad landscape of follicular lymphoma: Part II

Follicular lymphoma is a neoplasm derived from follicle center B cells, typically both centrocytes and centroblasts, in variable proportions according to the lymphoma grading. The pattern of growth may be entirely follicular, follicular and diffuse and rarely completely diffuse. It represents the second most common non-Hodgkin lymphoma, after diffuse large B-cell lymphoma and it is the most common low-grade mature B-cell lymphoma in Western countries. In the majority of cases, follicular lymphoma is a nodal tumor, occurring in adults and is frequently associated with the translocation t(14;18)(q32;q21)/IGH-BCL2. However, in recent years the spectrum of follicular lymphoma has expanded and small subsets of follicular lymphoma, which differ from common follicular lymphoma, have been identified and included in the current 2017 WHO classification. The aim of our review is to describe the broad spectrum of follicular lymphoma, pointing out that the identification of distinct clinicopathological variants of follicular lymphoma is relevant for the patient outcomes and treatment.

Pathology and diagnosis of follicular lymphoma and related entities

Follicular lymphoma (FL) is an indolent, mature B-cell neoplasm classically characterised by the t(14;18)(q32;q21) with constitutive overexpression of the anti-apoptotic protein, BCL2. Most cases present in older adults with slowly progressive lymphadenopathy and follow an indolent clinical course. Typical morphology shows an expansile follicular proliferation with tumour expression of germinal centre markers, and bone marrow involvement at diagnosis is frequent. However, in the recent past, efforts to understand the biological and clinical heterogeneity of FL has effected significant change to the diagnostic approach. While morphological grade, assessed by enumerating large 'centroblasts' in the neoplastic follicles, generally correlates with outcome in systemic nodal FL, variants with high-grade morphology but indolent clinical behaviour have been identified. Given the clinical implications of these FL variants, knowledge of their clinical and histopathological defining features is of paramount importance to the pathologist. Furthermore, as with many areas of diagnostic oncology, precursors to FL have been identified and described with measurable rates of progression to bona fide lymphoma. Accurate diagnosis of these early lesions can often prevent unnecessary therapy and guide appropriate monitoring for disease progression. This review aims to summarise these key pathological and diagnostic features of FL. We further highlight the biological underpinnings of FL that will likely affect the classification, diagnosis, and treatment of patients with lymphoma.

[Revised version of the 4th edition of the WHO classification of malignant lymphomas : What is new?]

After 8 years, the WHO has now published the updated version of the 4th edition of the classification of hematopoietic and lymphoid tumors. This update provides a conceptual rewrite of existing entities as well as some new provisional entities and categories, particularly among the aggressive B‑cell lymphomas. Important new diagnostic categories include the high-grade B‑cell lymphomas, the large B‑cell lymphoma with IRF4 rearrangement, and the Burkitt-like lymphoma with 11q aberrations. Of particular importance, new concepts concerning the taxonomy and classification of early lymphoid lesions or precursor lesions are included, such as the in situ follicular neoplasia or the in situ mantle cell neoplasia. In addition, the concept of indolent lymphoproliferations, such as breast-implant-associated anaplastic large cell lymphoma and the indolent T‑cell lymphoproliferative disorder of the gastrointestinal tract, has been strengthened. Finally, diagnostic criteria for existing lymphoma entities have been refined.

Primary testicular lymphoma: A SEER analysis of 1,169 cases

Primary testicular lymphoma (PTL) is a rare lymphoid malignancy. The present retrospective study aimed to investigate the demographic characteristics and survival of patients with PTL, as well as the associated prognostic factors, using a population-based database. All adults diagnosed with PTL in the Surveillance, Epidemiology, and End Results database were identified between 1973 and 2013. The Kaplan-Meier method was used to estimate cause-specific survival (CSS). Log-rank test or multivariate Cox regression model was used to assess the influence of demographic and clinical parameters on CSS. A total of 1,169 patients with PTL were identified from the database, and the median age was 70 years. The predominant histological subtype was diffuse large B-cell lymphoma, which affected 82.9% (970/1,169) of patients, and 68.6% (802/1,169) of patients had early stage disease (stages I–II). Patients >70 years, those diagnosed at the earlier time period, or those who had advanced-stage symptoms had the worst 5-year CSS rates; however, treatment with rituximab significantly improved the 5-year CSS. In conclusion, this retrospective study presented data from the largest cohort of patients with PTL and described the effects of rituximab on the CSS of patients with PTL.

Follicular Lymphoma Diagnostic Caveats and Updates

CONTEXT.—

Follicular lymphoma is a common small B-cell lymphoma, likely to be encountered by any practicing pathologist, regardless of specialty. Although the features of typical follicular lymphoma are well known and in most instances easily identifiable, there are lesser-appreciated morphologic appearances that can raise alternative diagnostic possibilities. The limited tissue available in core needle biopsies can make it additionally challenging to thoroughly evaluate those features in the context of architecture. Furthermore, ancillary testing including immunohistochemistry and molecular/genetic analysis do not always show classic findings and may pose additional challenges to interpretation.

OBJECTIVES.—

To review the morphologic features of follicular lymphoma with a discussion of morphologic variants and mimics; to discuss pitfalls of ancillary testing and provide the practicing pathologist with an appropriate context for interpretation of immunohistochemical and molecular/genetic studies when follicular lymphoma is part of the differential diagnosis; and to propose diagnostic strategies when there is limited tissue for evaluation.

DATA SOURCES.—

We used examples of follicular lymphoma from our institution as well as a review of the literature, with a focus on the diagnostic aspects that are broadly relevant to a general pathology practice.

CONCLUSIONS.—

Follicular lymphoma can occasionally present with atypical morphologic, immunohistochemical, or molecular/genetic features. In particular, those findings can be difficult to interpret in the setting of a limited tissue sample. Awareness of those possibilities will help guide the pathologist to a more accurate and precise diagnosis.

Clinicopathological features of primary splenic follicular lymphoma

Follicular lymphoma (FL) is a low-grade lymphoma that is usually characterized by generalized lymphadenopathy. Extranodal invasion by FL generally involves the bone marrow, skin, and duodenum; splenic infiltration often occurs in the advanced stages. However, primary splenic FL is very rare. Hence, few studies have been performed on splenic FL, and its clinicopathological features have not been established. This study aimed to investigate the clinicopathological features of primary splenic FL, as compared to nodal FL. We analyzed 17 patients diagnosed with primary splenic FL and 153 control patients with systemic FL. Hepatitis C virus (HCV)-positive status was significantly more common in patients with splenic FL than in the control patients (p = 0.02). Ann Arbor stage III or IV (p = 0.0003) and high-risk FLIPI (Follicular Lymphoma International Prognostic Index) (p = 0.03) were significantly less common in patients with splenic FL than in the control patients; however, the overall and progression-free survival curves were not significantly different between the groups. Among the 17 patients with splenic FL, the progression-free survival was significantly worse in patients who underwent splenectomy without receiving postoperative chemotherapy than in those who did (p = 0.03). These results suggest that primary splenic FL should be considered different from systemic FL; accordingly, its management should also be conducted differently.

Primary testicular lymphoma

Primary testicular lymphoma (PTL) is a rare, clinically aggressive form of extranodal lymphoma. The vast majority of cases are histologically diffuse large B-cell lymphoma, but rarer subtypes are clinically important and must be recognized. In this review, we discuss the incidence, clinical presentation, and prognostic factors of PTL and present a summary of the recent advances in our understanding of its pathophysiology, which may account for the characteristic clinical features. Although outcomes for patients with PTL have historically been poor, significant gains have been made with the successive addition of radiotherapy (RT), full-course anthracycline-based chemotherapy, rituximab and central nervous system–directed prophylaxis. We describe the larger retrospective series and prospective clinical trials and critically examine the role of RT. Although rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone given every 21 days with intrathecal methotrexate and locoregional RT is the current international standard of care, a substantial minority of patients progress, representing an unmet medical need. Finally, we discuss new treatment approaches and recent discoveries that may translate into improved outcomes for patients with PTL.

Pediatric-type nodal follicular lymphoma: an indolent clonal proliferation in children and adults with high proliferation index and no BCL2 rearrangement

Pediatric follicular lymphoma (PFL) is a variant of follicular lymphoma (FL) presenting as localized lymphadenopathy in children. Unlike conventional adult FL, PFL typically does not recur or progress. Clear diagnostic criteria for PFL are lacking, and it is uncertain whether this indolent lymphoma is defined by age or may occur in adults. We analyzed 27 FL in patients < 40 years of age and found that all 21 cases that lacked a BCL2 gene abnormality (BCL2-N; P < .0001) and had > 30% Ki67 fraction (high proliferation index, HPI; P = .0007) were stage I and did not progress or recur; in comparison, all 6 cases with BCL2 rearrangement and/or PI < 30% were stage III/IV, and 5 of 6 recurred or progressed. In a separate cohort of 58 adult FL (≥ 18 years of age), all 13 BCL2-N/HPI cases were stage I, and none progressed or relapsed, whereas 11 of 15 stage I cases with BCL2 gene abnormality and/or LPI relapsed or progressed (P = .0001). The adult and pediatric BCL2-N/HPI FL cases had similar morphologic features. Our results confirm the highly indolent behavior of PFL and suggest that these are characterized by HPI and absence of BCL2 gene abnormality. PFL-like cases also occur in adults and are associated with indolent behavior in this patient population.

Pathology of extra-nodal non Hodgkin lymphomas

In the management of extra-nodal lymphomas it is important to determine whether the tumour has disseminated and whether lymph nodes are involved. Some extra-nodal lymphomas may be the result of random spread of nodal lymphoma. Specific homing, however, determines the site of many extra-nodal lymphomas, as exemplified by cutaneous T-cell lymphomas, which seem to be derived from skin-homing T-cells and mucosa-associated lymphoid tissue lymphomas that show features of the mucosal immune system. Enteropathy-associated T-cell lymphoma is derived from mucosal T-cells in patients with coeliac disease. Immunological sanctuary accounts for the localisation of primary brain, eye and testicular lymphoma. Mantle cell lymphoma frequently causes tumours in the gastrointestinal tract. Random biopsies have shown that a high proportion of patients with this lymphoma have extensive occult involvement of the gastrointestinal tract at the time of first diagnosis. Follicular lymphoma occurs at both nodal and extra-nodal sites, but uncommonly at both sites at the same time. Extra-nodal follicular lymphomas frequently lack t(14;18)(q32;q21) and do not express bcl-2, which are characteristics of the nodal disease. At extra-nodal sites, follicular lymphoma is more likely to be curable than nodal follicular lymphoma. The behaviour of extra-nodal lymphomas cannot be assumed to follow that of their nodal counterparts.

Primary follicular lymphoma of the epididymis positive for t(14;18)(q32;q21)/IGH-BCL2 and negative for BCL2 protein expression: a case report

Introduction

Non-Hodgkin lymphoma (NHL) can involve the paratesticular organs as the primary disease, as primary testicular lymphoma that secondarily involves the paratesticular structures, as the initial site of presentation of occult nodal disease or as the result of disease dissemination. Primary follicular lymphoma of the epididymis in an adult is extremely rare. Little is known about primary adult paratesticular/epididimal lymphomas.

Case presentation

We report a rare case of primary follicular non-Hodgkin lymphoma of the epididymis in a 90-year-old Caucasian man who presented with a left scrotal mass. Bone marrow biopsy was negative and computed tomography of the total body revealed no evidence of extratesticular involvement. Macroscopically, the epididymis was replaced completely by a uniform mass. Histologic studies revealed a dense lymphoid infiltrate predominantly composed of centrocytes with admixed centroblasts. Immunohistochemical analyses demonstrated that neoplastic cells strongly expressed CD45RB, CD20, CD79a, bcl-6 and CD10; bcl-2 immunostaining was negative. Molecular studies showed the presence of the monoclonal IgH gene rearrangement and the IgH/BCL2 rearrangement. The lymphoma was classified as follicular lymphoma, low grade, grade 1-2. The patient subsequently underwent radical orchiectomy, did not receive chemotherapy and post-operative follow-up showed absence of disease recurrence.

Conclusions

The case of primary follicular lymphoma of epididymis, reported here, is considered a very rare event. It is characterized by clinically indolent localized disease, a good clinical outcome, lack of expression of BCL2 protein and the presence of the t(14;18)(q32;q21)/IGH-BCL2. Even if it is a single case, the primary follicular lymphoma epididymis with t(14;18) could represent either a variant of the previously reported t(14;18)-negative primary paratesticular follicular lymphoma or a distinct biological entity. To report additional cases in the future would be helpful in resolving this question.

B Cells Behaving Badly: A Better Basis to Behold Belligerence in B-Cell Lymphomas

A plethora of genetic abnormalities has been described in B-cell lymphomas, some of which arise when physiologic mechanisms involved in the generation of immunologic diversity go awry. Several different lymphoma types, such as follicular lymphoma (FL), mantle cell lymphoma (MCL), and Burkitt lymphoma (BL), are associated with hallmark translocations that occur as a consequence of these errors (t(14;18)(q32;q21), t(11;14)(q13;q32), and t(8;14)(q24;q32), respectively); however, none of these associations is absolute and none is completely diagnostically specific or sensitive. The advantages and limitations of a variety of different testing strategies in the 2 most common lymphomas, FL and diffuse large B-cell lymphoma (DLBCL), are reviewed herein, including an evaluation of the role of PCR-based approaches, FISH, and more nascent genomic technologies. The use of immunophenotypic strategies that may potentially provide, albeit imperfectly, more user-friendly surrogates for underlying genetic aberrations and cell-of-origin designations derived from gene-expression profiling analyses are also discussed. Finally, a newly designated category of lymphoma with features intermediate between DLBCL and BL is appraised, highlighting the central role of genetic analysis in this diagnostic gray zone.

Lymphoma classification: the quiet after the storm

The classification of malignant lymphomas remained controversial for over 30 years. The first scheme was proposed by Rappaport in the '60th and was based on incorrect histogenetic concepts. To overcome these limitations, several groups formulated new proposals in '70th. Among these two merited attention: the Lukes and Collins and the Kiel Classifications. They were based on the assumption that each lymphoma category might be related to a precise differentiation step of the lymphoid system, thus excluding any correlation with histiocytes, present on the Rappaport scheme. The Kiel Classification became very popular in Europe, while the one of Luke and Collins did not meet success in the United States (U.S.). In 1978, the National Cancer Institute proposed an international trial to compare the classifications used in Europe and U.S. The result was the genesis of the Working formulation, the tool for lymphoma classification in the U.S. up to the early '90th, but which was conversely rejected in Europe. In order to get over this lack of transatlantic communication, in 1994 the Revised European-American Lymphoma (REAL) Classification was proposed by the International Lymphoma Study Group. Its goal was to list "real" entities, each defined by the presence of homogeneous morphologic, phenotypic, cytogenetic, molecular, and clinical criteria, along with the possible recognition of its normal counterpart. The REAL Classification became the model for the WHO Classification of all haematopoietic tumours published in 2001. The present review aims to analyse future perspectives after the fourth edition of the WHO Classification released in 2008.

The efficacy of HGAL and LMO2 in the separation of lymphomas derived from small B cells in nodal and extranodal sites, including the bone marrow

We studied the efficacy of 2 germinal center B-cell markers, HGAL and LMO2, in the separation of lymphomas derived from small B cells, particularly follicular lymphoma (FL) and marginal zone lymphoma occurring in nodal, extranodal, splenic, and bone marrow sites using immunohistochemical analysis for CD10, BCL6, BCL2, HGAL, and LMO2. Our results showed that HGAL and LMO2 are sensitive and specific markers for detecting FL in nodal and extranodal sites. In contrast, all markers were down-regulated in FL infiltrates in the bone marrow. CD10 and HGAL were expressed in a subset of FLs in the bone marrow and were highly correlated with each other and with CD21, a marker of follicular dendritic cells. We conclude that HGAL and LMO2 should be considered in immunohistochemical panels used for the routine workup of lymphomas derived from small B cells. In the bone marrow, staining for HGAL or CD10 can be helpful in making a diagnosis of FL, although they are absent in a subset of cases.

Recent Advances in Follicular Lymphoma: Pediatric, Extranodal, and Follicular Lymphoma in Situ

Follicular lymphoma is a relatively common B-cell lymphoma composed of follicle center B lymphocytes. Follicular lymphomas occurring in the pediatric population and in some extranodal sites exhibit particular clinicopathologic features and clinical behavior that are often distinct from adult nodal follicular lymphoma. A type of "in-situ" follicular lymphoma presents as intrafollicular neoplastic cells in a background of architecturally normal lymphoid tissue and may be difficult to recognize in routine sections. Accurate recognition of the morphologic variants and clinicopathologic subtypes of follicular lymphoma is important to avoid confusing them with other lymphomas and reactive processes; in addition, some of these subtypes of follicular lymphoma display unusually indolent clinical behavior that warrant their separation from "conventional" follicular lymphoma.

The basis and rational use of molecular genetic testing in mature B-cell lymphomas

An increasing number of neoplasms are associated with variably specific genetic abnormalities. This is best exemplified by hematological malignancies, in which there is a growing list of entities that are defined by their genetic lesion(s); this is not (yet) the case in mature B-cell lymphomas. However, enhanced insights into the pathogenesis of this large and diverse group of lymphomas have emerged with the ongoing unraveling of a plethora of fascinating genetic abnormalities. The purpose of this review is to synthesize well-recognized data and nascent discoveries in our understanding of the genetic basis of a spectrum of mature B-cell lymphomas, and how this may be applied to contemporary clinical practice. Despite the explosion of new and exciting knowledge in this arena, with the potential for enhanced diagnostic and prognostic strategies, it is essential to remain cognizant of the limitations (and complexity) of genetic investigations, so that assays can be developed and used both judiciously and rationally.

Immunoarchitectural patterns in follicular lymphoma: efficacy of HGAL and LMO2 in the detection of the interfollicular and diffuse components

Follicular lymphoma (FL) can exhibit variant histologic patterns that can lead to confusion with other B-cell lymphomas and reactive conditions. Diagnostic markers such as CD10 and BCL2 may be difficult to interpret in variant FL patterns, and are often diminished or absent in the interfollicular and diffuse components. We evaluated 2 recently characterized germinal center B-cell markers, human germinal center associated lymphoma (HGAL), and LIM-only transcription factor 2 (LMO2), in 127 FL patient biopsies (94 nodal, 33 extranodal), and correlated the findings with histologic pattern, cellular composition, grade, and additional immunostains (CD20, CD3, CD21, CD10, BCL2, and BCL6). Architectural patterns included predominantly follicular (75%) and follicular and diffuse components (25%); 10 cases showed marginal zone differentiation and 3 were floral variants. Eighty-nine cases were low grade (38 grade 1; 51 grade 2) and 38 were grade 3 (29 grade 3A and 9 grade 3B). HGAL had the highest overall sensitivity of detecting FL and was superior in detecting the interfollicular and diffuse components compared with BCL2, LMO2, CD10, and BCL6. All 28 cases that lacked CD10, expressed HGAL, and the majority also expressed LMO2. Our results show that HGAL and LMO2 are sensitive markers for FL diagnosis. The addition of HGAL and LMO2 to the immunohistologic panel is beneficial in the work-up of nodal and extranodal B-cell lymphomas and the efficacy of HGAL in detecting the follicular, interfollicular and diffuse components of FL is of particular value in the setting of variant immunoarchitectural patterns.

Primary testicular diffuse large B-cell lymphoma shows an activated B-cell-like phenotype

The most common type of primary testicular lymphoma is diffuse large B-cell type, which has a poor prognosis relative to other extra-nodal diffuse large B-cell lymphomas (DLBCL). These constitute a heterogeneous group of lymphomas with germinal center B-cell-like and activated B-cell-like subtypes. Such a distinction theoretically utilizes the immunohistochemical expression of CD10, Bcl-6, and MUM1. The purpose of this study was that we could stratify primary testicular lymphoma of diffuse large B-cell type according to this scheme, and further elucidate the reason why primary testicular diffuse large B-cell lymphoma possesses a poor clinical outcome. Seventeen Chinese patients with primary testicular DLBCL were examined by means of a 3-antibody panel (CD10, Bcl-6, MUM1). Among these 17 cases, 16 were assigned to the activated B-cell-like subtypes. One case was classified as germinal center B-cell-like type. Twelve of these 17 cases expressed high proliferative activity (>or=40% Ki-67 labeling). The majority of primary testicular DLBCLs have activated B-cell-like subtype characteristics and high proliferative activity. These features might be a significant factor; moreover, they are associated with poor prognosis.

Unusual scrotal pathology: an overview

The diverse embryological origins of the contents of the scrotum create an environment that fosters a wide variety of unusual pathologies. Most scrotal pathologies are discovered by the patient and are initially evaluated by a thorough physical examination and scrotal ultrasonography. Scrotal lesions can be broadly grouped by the anatomical location in which they develop; the clinician must consider a wide differential diagnosis based on this location. Solid testicular masses are considered germ cell tumors until proven otherwise, but numerous other possible pathologies exist, including ectopic tissue, metastasis, and other neoplastic growths. Rete testis lesions are classified as developmental, benign or malignant. Cystic lesions of the epididymis are most commonly benign, but malignant neoplasms can also be present. The paratesticular region has the broadest differential diagnosis, as it contains numerous distinct structures and is a common location for ectopic tissue and metastatic disease; a narrower range of lesions develop in the scrotal wall because of its simpler anatomy. Treatment options range from conservative observation to wide surgical excision and should be considered carefully; the aim of therapy is to remove malignant or potentially malignant tissue while minimizing effects on fertility and function.

Low stage follicular lymphoma: biologic and clinical characterization according to nodal or extranodal primary origin

Studies suggest that primary extranodal follicular lymphoma (FL) is not infrequent but it remains poorly characterized with variable histologic, molecular, and clinical outcome findings. We compared 27 extranodal FL to 44 nodal FL using morphologic, immunohistochemical, and molecular genetic techniques and evaluated the clinical outcome of these 2 similarly staged groups. Eight cases of primary cutaneous follicle center lymphoma were also studied. In comparison to nodal FL, a greater number of extranodal FL contained a diffuse growth pattern (P=0.004) and lacked CD10 expression (P=0.014). Fifty-four percent of extranodal and 42% of nodal FL cases showed evidence of t(14;18), with minor breakpoints (icr, 3'BCL2, 5'mcr) more commonly found in extranodal cases (P=0.003). Outcome data showed no significant differences in overall survival (P=0.565) and progression-free survival (P=0.627) among extranodal, nodal, and primary cutaneous follicle center lymphoma cases. Analysis of all cases by t(14;18) status indicate that the translocation-negative group is characterized by a diffuse growth pattern (P=0.043) and lower BCL2 expression (P=0.018). The t(14;18)-positive group showed significantly better overall survival (P=0.019) and disease-specific survival (P=0.006) in comparison with the t(14;18)-negative group. In low stage FL, the status of t(14;18) seems to be more predictive of outcome than origin from an extranodal versus nodal site.

Benign and Malignant Neoplasms of the Testis and Paratesticular Tissue

Benign and malignant tumors of the testes and paratesticular tissues present an interesting spectrum of diagnostic entities often encountered in routine surgical pathology practice. Germ cell tumors are the most common tumors of the testes and, despite a rising incidence, have excellent prognosis because of their radiosensitivity and/or effective chemotherapeutic agents. The proper classification of these tumors aids in the choice of appropriate treatment options. This article reviews benign and malignant neoplastic entities of the testes and paratesticular tissues and illustrates the classic pathologic characteristics. The differential diagnosis, along with ancillary studies, clinical significance, and presentation are discussed also.

Follicular lymphoma of the thyroid gland

The majority of lymphomas arising in the thyroid gland are mucosa-associated lymphoid tissue lymphomas and diffuse large B-cell lymphomas, which arise from a background of chronic lymphocytic thyroiditis. Follicular lymphoma may also present in the thyroid gland, but its clinicopathologic features at this site are not well characterized, leading to difficulties in diagnosis and clinical management. We have addressed this problem by studying the clinical, morphologic, immunophenotypic, and genetic features of 22 such cases. All cases showed morphology characteristic of follicular lymphoma, however, in many the interfollicular neoplastic infiltrate was particularly prominent and all lymphomas contained readily identifiable and often striking lymphoepithelial lesions, features heretofore considered indicative of mucosa-associated lymphoid tissue lymphoma at this site. Furthermore, 13 of 18 cases for which sufficient evidence was available had clinical and/or histologic evidence of chronic lymphocytic thyroiditis. Analysis of genetic and immunohistochemical features identified 2 distinct groups. In 1 group, similar to typical adult follicular lymphoma, cases carried a t(14;18)/IGH-BCL2 and/or expressed Bcl-2, and were mostly CD10-positive and of World Health Organization (WHO) grade 1 to 2. Follicular lymphomas in the other group lacked IGH-BCL2 and Bcl-2 expression, were often of WHO grade 3 and were often CD10-negative, similar to the minority of follicular lymphomas previously described that are Bcl-2-negative and are often encountered at other extranodal sites. The 2 groups differed in clinical stage at presentation, 11 patients in the former group but none in the latter group having disease beyond the thyroid gland. Appreciation of the spectrum of morphologic, immunophenotypic, and genetic characteristics of follicular lymphoma presenting in the thyroid gland should aid both diagnosis and clinical management.

Extranodal lymphoma

Lymphomas arising in extranodal sites are intriguing. The types of lymphomas encountered vary widely from one extranodal site to another. For many types of extranodal lymphomas, there are distinctive clinicopathologic features, sometimes including association with an underlying immunodeficiency syndrome, autoimmune disease, infection, or other immunologic disorder, or a predilection to affect patients of certain ethnic origins. Presented below is a review of lymphomas that are encountered most often in extranodal sites.

Testicular Tumors—Some New and a Few Perennial Problems

The histopathology of testicular tumors is presented, emphasizing new, unusual, or underemphasized aspects. Within the category of seminoma of the usual type, the recent literature has drawn attention to the presence in occasional tumors of solid or hollow tubules or spaces of varying sizes and shape that may result in cribriform or microcystic patterns, causing potential confusion with other neoplasms, most notably Sertoli cell tumor or yolk sac tumor. Although regions of typical neoplasia and awareness of this phenomenon usually will be diagnostic, immunohistochemistry may play a role in excluding Sertoli cell tumor or yolk sac tumor. Although immunohistochemistry can play an undoubted helpful role in this and selected other areas of testicular tumor evaluation, careful evaluation of the gross and routine microscopic features will solve the vast majority of diagnostic problems. An excellent review of immunohistochemistry in this area by R. E. Emerson, MD, and T. M. Ulbright, MD, is cited herein. Spermatocytic seminoma remains a crucial pitfall in diagnosis, and the pathologist must always be alert to the possible diagnosis when looking at a seminomatous neoplasm, particularly in an older patient, although about one third of these tumors occur in the usual seminoma age range. The embryonal carcinoma has a great diversity of patterns, which are briefly noted. The enigmatic and picturesque tumor, polyembryoma, which virtually never occurs in pure form but may be a confusing component of a variety of mixed germ cell tumors, is discussed and illustrated. The phenomenon of burnt-out germ cell neoplasia is also briefly noted and an excellent recent contribution is referred to. Within the sex cord–stromal family of neoplasms, recent contributions and elaborations of unusual morphologic features of Leydig cell tumors and Sertoli cell tumors are presented. Within the Leydig cell family, cyst formation, adipose metaplasia, calcification or ossification, and spindle cell patterns may be particularly confusing, and in the Sertoli cell family, a great array of patterns caused by differing admixtures of tubular, solid, and stromal components occur. The peculiar lesion, intratubular large cell hyalinizing Sertoli cell tumor, of young boys with Peutz-Jeghers syndrome, is briefly discussed. Some of the problems in the family of hematopoietic neoplasms are reviewed, these processes posing diverse problems in differential diagnosis and their correct recognition having crucial therapeutic implications. Although secondary tumors to the testis have not received the same attention in the literature as the similar phenomenon in the female gonad, remarkable examples of testicular spread of diverse neoplasms, usually carcinoma but rarely melanoma, are seen, and the pathologist should be alert to this possibility, particularly when examining an unusual morphology in an older patient. Finally, a few comments are made on the common paratesticular neoplasm, the adenomatoid tumor, highlighting its varied patterns and recent description of some of the issues that may arise when they undergo total or subtotal infarction.

Clinical Features, Prognosis and Treatment of Follicular Lymphoma

Follicular lymphoma constitutes the most frequent indolent lymphoma, well characterized by its clinical presentation related to nodal involvement and its morphologic and biologic features. Some rare locations of extranodal involvement, such as the gastrointestinal tract or skin, were recently further refined. The description of the Follicular Lymphoma International Prognostic Index (FLIPI) represents an important step in identifying patient subgroups with predictable outcome and comparing the results of clinical trials, although its use in clinical practice remains to be established. Analyses of gene expression profiles or constitutive gene variations may also provide additional insights for prognostication in the near future. Furthermore, these data underline the complex interactions between the tumor cells and their microenvironment; recent attempts to translate these findings with immunohistochemical studies remain unable to robustly predict patient outcome. The therapeutic strategies in follicular lymphoma have been transformed by monoclonal antibodies, used alone or in combination with chemotherapy. Treatment options should be adapted to the clinical features at diagnosis and appear to be able to modify the overall survival of some subgroups of patients. Further efforts may focus on strategies that can alter the natural history of this disease.