Cutaneous follicular B-cell lymphoma: description of a series of 18 cases

Primary Cutaneous B-Cell Lymphomas with Large Cell Morphology: A Practical Review

Most primary cutaneous lymphomas consist of T-cell lymphomas or small cell lymphomas; however, the skin may also be affected by lymphomas with large cell morphology, as a primary or secondary localization. A minority of cases consist of primary cutaneous B-cell lymphomas (PCBCLs). PCBCLs are a heterogeneous group of rare neoplasms with an overlapping morphological and immunohistochemical picture of the different subtypes. Nevertheless, differential diagnosis in the setting of this group of neoplasms is mandatory to identify the correct therapy and prognosis, but it may be challenging since, due to the rarity of these neoplasms, they may not always be familiar to pathologists. Indeed, immunohistochemistry may not be enough to distinguish the different histotypes, which overlap in immunohistochemical features. Furthermore, the ever-increasing knowledge of the molecular features of systemic B-cell lymphomas, such as gene rearrangements with clinical significance, has led in recent years to further investigation into the molecular landscape of PCBCLs with large cell morphology. This work aimed to provide a practical diagnostic guide for pathologists dealing with primary cutaneous large B-cell lymphomas.

Diagnostic value of STMN1, LMO2, HGAL, AID expression and 1p36 chromosomal abnormalities in primary cutaneous B cell lymphomas

AIMS

Distinction between primary cutaneous follicular lymphoma (PCFL) and primary cutaneous marginal zone lymphoma (PCMZL) is challenging, as clear-cut immunophenotypical and cytogenetic criteria to segregate both entities are lacking.

METHODS AND RESULTS

To characterize PCFL and PCMZL more clearly and to define criteria helpful for the differential diagnosis, we compared expression of immunohistochemical markers [LIM-only transcription factor 2 (LMO2), human germinal centre-associated lymphoma (HGAL), stathmin 1 (STMN1), activation-induced cytidine deaminase (AID), myeloid cell nuclear differentiation antigen (MNDA)] and the presence of cytogenetic abnormalities described previously in nodal follicular lymphoma [B cell lymphoma 2 (BCL2) and BCL6 breaks, 1p36 chromosomal region deletion (del 1p36)] in a series of 48 cutaneous follicular and marginal zone lymphomas [cutaneous follicular lymphoma (CFL) and cutaneous marginal zone lymphoma (CMZL)]. Immunostaining for STMN1, LMO2, HGAL and AID allowed the distinction between CFL and CMZL, and STMN1 was the most sensitive marker (100% CFL, 0% CMZL). LMO2, HGAL and AID were positive in 93.2%, 82.1% and 86.2% CFL (all CMZL-negative). MNDA was expressed in both entities without significant difference (10.3% CFL, 30.8% CMZL, P = 0.18). BCL2, BCL6 breaks and the del 1p36 were present in 16.7%, 10.7% and 18.5% CFL and no CMZL. Finally, three and 29 CFL were reclassified as secondary cutaneous follicular lymphomas (SCFL) and PCFL without significant differences concerning phenotypical and cytogenetic features. BCL2, BCL6 breaks and the del 1p36 were present in 11.1%, 8% and 16.7% PCFL and did not impact the prognosis.

CONCLUSION

LMO2, HGAL, STMN1 and AID, but not MNDA, are discriminant for the recognition between CFL and CMZL. BCL2, BCL6 rearrangements and the del 1p36 have a role in the pathogenesis of PCFL, the latest being the most common alteration.

Primary cutaneous B-cell lymphomas with large cell predominance-primary cutaneous follicle center lymphoma, diffuse large B-cell lymphoma, leg type and intravascular large B-cell lymphoma

In this review, we present clinical features and detailed histopathologic, immunologic, and molecular information regarding primary cutaneous follicle center lymphoma and primary cutaneous diffuse large B-cell lymphoma, leg type which together represent two of the three most common types of primary cutaneous B-cell lymphoma recognized in the current WHO classification system.^1,2 Overall, B-cell lymphomas represent 19-27% of primary cutaneous lymphomas in most large European and American studies^3-6 and together, primary cutaneous follicle center lymphoma and primary cutaneous diffuse large B-cell lymphoma, leg type account for approximately 2/3 to ¾ of these cases.^5,7-11 Both subtypes can contain a high content of large B-lymphocytes, although most cases of primary cutaneous follicle center lymphomas exhibit a range in cell size and cytology. Intravascular large B-cell lymphoma, a less commonly-encountered EBV-negative primary cutaneous B-cell lymphoma composed of large cells, will be more briefly discussed in this report as well.

Primary Cutaneous Follicle Center Lymphomas Expressing BCL2 Protein Frequently Harbor BCL2 Gene Break and May Present 1p36 Deletion: A Study of 20 Cases

The classification of cutaneous follicular lymphoma (CFL) into primary cutaneous follicle center lymphoma (PCFCL) or secondary cutaneous follicular lymphoma (SCFL) is challenging. SCFL is suspected when tumor cells express BCL2 protein, reflecting a BCL2 translocation. However, BCL2 expression is difficult to assess in CFLs because of numerous BCL2+ reactive T cells. To investigate these issues and to further characterize PCFCL, we studied a series of 25 CFLs without any extracutaneous disease at diagnosis, selected on the basis of BCL2 protein expression using 2 BCL2 antibodies (clones 124 and E17) and BOB1/BCL2 double immunostaining. All cases were studied using interphase fluorescence in situ hybridization with BCL2, BCL6, IGH, IGK, IGL breakapart, IGH-BCL2 fusion, and 1p36/1q25 dual-color probes. Nineteen CFLs were BCL2 positive, and 6 were negative. After a medium follow-up of 24 (6 to 96) months, 5 cases were reclassified as SCFL and were excluded from a part of our analyses. Among BCL2+ PCFCLs, 60% (9/15) demonstrated a BCL2 break. BCL2-break-positive cases had a tendency to occur in the head and neck and showed the classical phenotype of nodal follicular lymphoma (CD10+, BCL6+, BCL2+, STMN+) compared with BCL2-break-negative PCFCLs. Del 1p36 was observed in 1 PCFCL. No significant clinical differences were observed between BCL2+ or BCL2- PCFCL. In conclusion, we show that a subset of PCFCLs harbor similar genetic alterations, as observed in nodal follicular lymphomas, including BCL2 breaks and 1p36 deletion. As BCL2 protein expression is usually associated with the presence of a BCL2 translocation, fluorescence in situ hybridization should be performed to confirm this hypothesis.

Primary cutaneous B-cell lymphomas: part I. Clinical features, diagnosis, and classification

Primary cutaneous B-cell lymphomas (PCBCLs) are defined as lymphomas with a B-cell phenotype that present in the skin without evidence of systemic or extracutaneous disease at initial presentation, after adequate staging. In non-Hodgkin lymphomas, the skin is the second most common site of extranodal involvement after the gastrointestinal tract. PCBCLs are histologically very similar to their nodal counterparts, and these histologic similarities can lead to confusion about both therapy and prognosis. This article will summarize the clinical, pathologic, and diagnostic features of the 3 main types of PCBCL: primary cutaneous follicle center lymphoma, primary cutaneous marginal zone lymphoma, and primary cutaneous diffuse large B-cell lymphoma, leg-type, and the appropriate evaluation and staging procedures for each of these entities.

Radiotherapy of primary cutaneous follicle center lymphoma: case report and review of literature

Primary cutaneous follicle center lymphoma is an indolent primary cutaneous B-cell lymphoma originating from the follicle center cells, composed of a combination of centrocytes (small and large cleaved cells) and centroblasts (large noncleaved cells) with a follicular, follicular/diffuse, or diffuse growth pattern. Lesions are mostly located on the head, neck and trunk. A case is presented of a 56-year-old male patient with primary cutaneous follicle center lymphoma, with lesions involving the skin of the back, shoulders, presternal area and right forearm. As the patient presented a disseminated cutaneous form of the disease that involved several anatomical regions, complete work-up was followed by superficial fractionated radiotherapy of eight fields in VI expositions, with total irradiation dose of 1400 cGy upon the following fields: right and left pectoral region, left and right shoulders, right suprascapular region, and proximal third of the right forearm. Total irradiation dose applied upon each field for the lesions located on the left and right side of the back was 1500 cGy. This therapy resulted in significant reduction of visible tumor. The patient was regularly followed up on outpatient basis for 12 months of radiotherapy, being free from local recurrence and systemic spread of the disease.

Primary Non-Hodgkin's Lymphoma of the Scalp and Cranial Vault

Primary Non-Hodgkin's Lymphoma of the cranial scalp and skull vault is a rare disease. We are describing a case of the same in a 50-year-old man. He was presented with a diffuse swelling in the left side scalp since 4 months of duration and progressively enlarging in size. On local Examination of the scalp, there was a diffuse swelling in the left parietal and occipital region of scalp. Imaging showed diffuse infiltration of the skull vault with extracranial soft tissue masses. Further investigations with CT scan chest, abdomen, and pelvis did not reveal any other evidence of systemic lymphoma. Biopsy of one of the scalp masses showed a small to intermediate cell B-cell lymphoma. Other nine previously reported cases of primary skull vault lymphoma were reviewed.

Composite chronic lymphocytic leukemia/small lymphocytic lymphoma and follicular lymphoma are biclonal lymphomas: a report of two cases

Composite lymphomas (CLs) consisting of 2 indolent B-cell lymphomas are rare. We present 2 CL cases composed of chronic lymphocytic leukemia (CLL) and follicular lymphoma (FL), each with unique clinicopathologic features. In the first case, the FL was negative for IGH-BCL2 and harbored a novel IGH-associated translocation; in the second case, the CL manifested in the skin. The individual components in both CLs were derived from different B-cell clones. This is the first complete characterization, including molecular analysis, of CLs composed of leukemic CLL and FL and the first report of a cutaneous CL derived from 2 low-grade B cell lymphomas. Our results provide additional supporting evidence that CLs of indolent B-cell lymphomas are biclonal and suggest that they are pathogenetically different from CLs composed of a low-grade B-cell lymphoma and an aggressive B-cell lymphoma or Hodgkin lymphoma, which are usually clonally related.

Comments on cutaneous lymphomas: since the WHO-2008 classification to present

The last classification of lymphomas of the World Health Organization in 2008 made a few changes from the preceding classification. Although useful, at the same time, it has posed new questions, concerns, and dilemmas which have been raised in the literature. The current report highlights some of these controversies, of each of these primary cutaneous entities, going through cutaneous mature T-cell and NK-cell neoplasms, mature B-cell neoplasms, precursor neoplasms, and other entities, which for several reasons do not fit in the previous categories. It also reviews some advances on many of these lymphomas published in the last 2 years.

Gastrointestinal follicular lymphoma: review of the literature

Gastrointestinal follicular lymphoma (GI-FL) is a relatively rare disease, accounting for only 1%-3.6% of gastrointestinal non-Hodgkin's lymphoma. Although the duodenum and terminal ileum are considered to be the most common sites of origin, the development of wireless capsule endoscopy and double-balloon enteroscopy has increased the detection of GI-FL in every part of the small intestine. Approximately 70% of patients with GI-FL are estimated to have multiple lesions throughout the entire gastrointestinal tract. FL is a low-grade lymphoma that usually develops very slowly. If the lymphoma causes no symptoms, immediate treatment may not be necessary. Standard therapy has not yet been established for GI-FL, but chemotherapy, radiotherapy, monoclonal antibody therapy, or a combination of these therapies, is sometimes performed based on the therapeutic regimens for nodal FL. Regimens including conventional chemotherapy with rituximab, which achieve high response rates in nodal FL, are commonly used for GI-FL. The long-term clinical outcome of GI-FL is unclear. The results of a few series on the long-term outcomes of patients with GI-FL treated with conventional therapy indicate a median relapse-free time ranging from 31 to 45 months. On the other hand, in patients with GI-FL who were followed without treatment, the median time to disease progression was 37.5 months. Thus, whether to initiate aggressive therapy or whether to continue watchful waiting in patients with GI-FL is a critically important decision. Ongoing research on biomarkers to guide individualized GI-FL therapy may provide invaluable information that will lead to the establishment of a standard therapeutic regimen.

Immunocytochemistry and the diagnosis of cutaneous lymphoma

Cutaneous lymphoid infiltrates may pose some of the most difficult diagnostic problems in dermatopathology. Immunocytochemistry is often employed in an effort to determine whether an infiltrate is neoplastic or, in the case of clearly malignant infiltrates, to provide a specific diagnosis. The rarity of these disorders and the variant immunocytochemical profiles they may present further thwart understanding and sometimes prevent an accurate diagnosis. In this review the common immunocytochemical profiles of various cutaneous lymphomas are presented and potential pitfalls and problems considered. Immunocytochemistry is not a diagnostic test but, as in other areas of histopathology, is a highly valuable tool that requires critical interpretation within a context: so applied, it is an indispensable part of the pathologist's arsenal in evaluating lymphoid infiltrates and defining different lymphomas.

European Organization for Research and Treatment of Cancer and International Society for Cutaneous Lymphoma consensus recommendations for the management of cutaneous B-cell lymphomas

Primary cutaneous B-cell lymphomas (CBCL) represent approximately 20% to 25% of all primary cutaneous lymphomas. With the advent of the World Health Organization-European Organization for Research and Treatment of Cancer (EORTC) Consensus Classification for Cutaneous Lymphomas in 2005, uniform terminology and classification for this rare group of neoplasms were introduced. However, staging procedures and treatment strategies still vary between different cutaneous lymphoma centers, which may be because consensus recommendations for the management of CBCL have never been published. Based on an extensive literature search and discussions within the EORTC Cutaneous Lymphoma Group and the International Society for Cutaneous Lymphomas, the present report aims to provide uniform recommendations for the management of the 3 main groups of CBCL. Because no systematic reviews or (randomized) controlled trials were available, these recommendations are mainly based on retrospective studies and small cohort studies. Despite these limitations, there was consensus among the members of the multidisciplinary expert panel that these recommendations reflect the state-of-the-art management as currently practiced in major cutaneous lymphoma centers. They may therefore contribute to uniform staging and treatment and form the basis for future clinical trials in patients with a CBCL.

BCL2 gene abnormalities define distinct clinical subsets of follicular lymphoma

AIMS

Follicular lymphoma (FL) arising primarily in the skin has recently been proposed as a distinct entity on the basis of a low incidence of t(14;18)(q32;q21) and bcl-2 expression, with a very high percentage of patients surviving more than 5 years. However, cases of t(14;18)(q32;q21)-positive primary cutaneous FL (PCFL) and examples of t(14;18)(q32;q21)-negative FL at nodal and other extranodal sites, are well documented. The aim of this study was to test the hypothesis that there is a subtype of FL lacking t(14;18)(q32;q21), which preferentially involves certain sites but is not restricted by anatomical location.

METHODS AND RESULTS

A cohort of 47 stage 1 FL was stratified according to the presence or absence of t(14;18)(q32;q21) using conventional cytogenetics, polymerase chain reaction and interphase fluorescence in situ hybridization. Compared with t(14;18)(q32;q21)-positive cases, FL lacking the translocation were less likely to express CD10 or bcl-2 (P<0.01), made up a significantly greater proportion of cases arising at extranodal sites (P<0.001) and had a significantly better overall and disease-specific 5-year survival (P<0.01).

CONCLUSIONS

These results support the concept of a subtype of FL lacking t(14;18)(q32;q21), characterized by low-intensity bcl-2 expression, a predilection for extranodal sites, particularly the skin, and a more favourable outcome than t(14;18)(q32;q21)-positive FL.

Cytogenetic and Molecular Analysis of 12 Cases of Primary Cutaneous Marginal Zone Lymphomas

Primary low-grade B-cell lymphomas of the skin are separated into marginal zone and follicle center lymphomas according to the recent World Health Organization-European Organization for Research and Treatment of Cancer classification, with distinct histologic and immunohistochemical profiles. Some cases remain difficult to distinguish. The degree of relationship with their extracutaneous counterparts is currently being investigated on clinical, histologic and molecular grounds. Cytogenetic analysis using fluorescence in situ hybridization was performed on 12 frozen samples of infiltrated skin that had been classified as marginal zone lymphoma (MZL). Chromosomal changes known to be recurrently observed in systemic MZL of the mucosa-associated lymphoid tissue type, and in follicular center lymphoma were analyzed. These included trisomy for chromosomes 3, 7, 12, and 18 as well as t(14;18) IGH/BCL2, t(14;18) IGH/MLT1, and t(11;18) API2/MLT1 translocations. Complementary molecular search of IGH/BCL2 rearrangement using a polymerase chain reaction technique and of API2/MLT1 mRNA expression by reverse transcriptase-polymerase chain reaction were performed. Two cases showed evidence of trisomy 3 at levels varying from 14% to 20% of the analyzed cells. No other chromosomal abnormalities were found with those techniques in the remaining cases. These results demonstrate that known recurrent chromosomal abnormalities rarely occur in primary cutaneous MZLs and suggest the possibility of a variety of initial oncogenic events leading to a common downstream pathway. These data also underline that fluorescence in situ analysis on routine skin punch biopsies represents a reliable tool for the detection of chromosomal changes, but requires consistent dermal infiltration.

Molecular cytogenetic evidence of t(14;18)(IGH;BCL2) in a substantial proportion of primary cutaneous follicle center lymphomas

In contrast to nodal follicular lymphoma, limited data exist on genetic changes in primary cutaneous follicular lymphoma (primary cutaneous follicle center lymphoma according to WHO-EORTC). The detection rate of the BCL2 rearrangement, representing the characteristic t(14;18)(q32;q21) underlying follicular lymphoma, by polymerase chain reaction (PCR) has been reported to vary over a wide range (0%-41%), and only a few cases have been studied by molecular cytogenetic techniques such as fluorescence in situ hybridization (FISH). In this study, 27 primary cutaneous follicle center lymphomas were analyzed by FISH and the results compared with those obtained by PCR. FISH demonstrated translocations affecting the immunoglobulin heavy chain locus (IGH) in 14 of 27 cases (52%): a t(14;18)(q32;q21) involving BCL2 was found in 11 cases (41%), a t(3;14)(q27;q32) affecting BCL6 in 2 cases (7%), and in 1 case the partner gene of IGH could not be identified. Interestingly, PCR did not detect BCL2 rearrangement in any case. These data suggest that the t(14;18)(q32;q21) frequently occurs in primary cutaneous follicular lymphoma. The reason(s) why BCL2 rearrangements escape the detection by PCR is (are) not clear but could be due to BCL2 mutations, breakpoints outside the amplified DNA, or a high load of somatic mutations.

Update on extranodal lymphomas. Conclusions of the Workshop held by the EAHP and the SH in Thessaloniki, Greece

Classification and proper treatment of extranodal lymphoma is hindered by the diversity of lymphoma types and the relative rarity of many of these tumour types. In order to review controversial issues in extranodal lymphoma diagnosis, a joint Workshop of the European Haematopathology Association (EAHP) and the Society for Hematopathology (SH) was held, where 99 selected cases were reviewed and discussed. This Workshop summary is focused on the most controversial aspect of cutaneous B-cell lymphoma, other extranodal B-cell lymphomas, plasmablastic lymphoma and anaplastic large-cell lymphoma in extranodal sites, and makes practical recommendations about diagnosis and therapeutic approaches.

Lymphomes B cutanés primitifs : corrélations anatomo-cliniques dans une série de 44 cas

AIMS

histological and clinical relationship study of 44 cases of primary cutaneous B cell lymphoma, classified according to WHO classification.

MATERIALS AND METHODS

histological, immunological and molecular analysis was correlated with clinical data.

RESULTS

33 cases (75%) were marginal zone B-cell lymphomas (MZL), with head and trunk predominance (median age = 54 years). Relapses in other mucosa-related sites occurred in 3 patients. Histological transformation implied a more aggressive treatment in 3 cases. A favorable outcome was observed in most cases. 9 (20%) diffuse large B-cell lymphomas (DLBCL) appeared as a unique nodule, with female predominance (median age = 74 years) and 4 lymphoma-related deaths which seemed age-related (> 70 years) with only one lower limb localization. Histological aggressive features were present in 3 patients with a fatal outcome. 2 (5%) WHO grade 3 follicular lymphomas (FL) had an heterogeneous phenotype, with head localization, cutaneous relapses and good outcome.

CONCLUSIONS

MZL, the predominant type, has a good prognosis, although transformation can occur, needing a more aggressive treatment. DLBCL, observed in older patients, has clinical and histological prognostic factors identical to extra-cutaneous lymphomas. FL appears rare and has an heterogeneous phenotype. Relationships with its nodal counterpart remains unclear.

Clinicopathologic, Immunophenotypic, and Molecular Cytogenetic Fluorescence In Situ Hybridization Analysis of Primary and Secondary Cutaneous Follicular Lymphomas

Although primary cutaneous follicular lymphoma (FL) is considered a distinct variant of FL in the World Health Organization classification ("cutaneous follicle center lymphoma"), its biologic relationship to nodal FL remains controversial. The clinical, morphologic, immunophenotypic, and molecular cytogenetic features of 17 patients with primary cutaneous FL were studied and compared with 16 patients with secondary cutaneous FL. The head and neck region was the most frequent site at initial skin presentation in both the primary and secondary cases. Among the primary cases, 29% of the 31 biopsies were grade 1, 48% grade 2, 13% grade 3, and 10% grade 3 with diffuse large B-cell (DLBCL) areas. Among the secondary cases, 38% of the 29 skin biopsies were grade 1, 45% grade 2, 3% grade 3, and 7% grade 3 with DLBCL areas with two not evaluable. A floral-like pattern was observed in 32% of primary FL but only 5% of secondary cases. Histologic progression was found in 21% of patients. CD10 expression was demonstrated in 90% (27 of 30) of primary cases and 96% (22 of 23) of secondary cases. Bcl-6 was expressed in all cases tested. Bcl-2 expression was detected in 57% (17 of 30) of the primary cases (100% of grade 1, 43% of grade 2, 40% of grade 3), whereas all secondary cases were bcl-2 positive (P=0.0002). The t(14;18) translocation was identified by interphase fluorescence in situ hybridization (FISH) in biopsies from 31% (4 of 13) of the patients with primary FL compared with 77% (10 of 13) of those with secondary lymphoma (P <0.05). Seven of the 17 (41%) patients with primary disease had cutaneous relapse, including 1 who also developed nodal disease. Bcl-2 positivity was seen in 4 of these 7 patients. Eight of the 16 (50%) patients with secondary FL had cutaneous relapse. Primary and secondary cutaneous FL share many clinical and phenotypic features, but primary cases may have some distinctive morphologic features, more frequently lack bcl-2 protein, and often lack the t(14;18) translocation. These findings suggest that primary cutaneous FL are distinctive and often but not always have a pathogenesis different from most of nodal and secondary cutaneous FL.

Pathology of Primary Cutaneous B-Cell Lymphomas: Diagnosis and Classification

The skin is the second most common extranodal site for non-Hodgkin's lymphomas. Therefore, hematologists, pathologists, and dermatologists need to be familiar with these lymphomas. Primary cutaneous B-cell lymphomas are less common than T-cell lymphomas but have received much attention in the past few years. Their typical clinical and pathologic features are becoming clear. However, there is still some disagreement in terminology and characteristics of these lymphomas between the World Heath Organization (WHO) classification and the European Organisation for Research and Treatment of Cancer (EORTC) proposal for primary cutaneous lymphomas. This review will focus on the features of primary cutaneous B-cell lymphomas, compare and contrast areas of discordance between the WHO and EORTC systems, and outline areas for further investigation.

Follicular lymphoma of the skin and superficial soft tissues associated with a prominent follicular dendritic cell proliferation: an unusual pattern which may represent a diagnostic pitfall

We describe two elderly patients with follicular lymphoma (FL) involving the skin and superficial soft tissues, with a striking proliferation of follicular dendritic cells (FDC). In addition, one patient had bone marrow involvement by FL. Histopathologically, the most remarkable feature in both cases seen at low magnification was a striking pallor of the constituent cells, which were arranged in fascicles, whorls, and round islands. The majority of the cells had the typical cytologic features of FDCs. They were intimately intermingled with centroblasts and centrocytes. A large amount of the clear cytoplasm and the pale nuclei of FDCs, which predominated in the tumors, caused the striking overall pallor of the lesions. Small reactive lymphocytes were scattered between the fascicles. A vague follicular growth pattern was seen only focally. The mantle zones were markedly reduced or absent so that the follicles were seen lying unseparated. The close intermixture of the FDCs and the germinal center cells was responsible for the FDCs appearing to be decorated with B-associated marker, and the germinal center cells seemed to be stained to some degree with FDC-markers. The tumor bulk demonstrated a diffuse and strong reaction with CD10, CD20, CD21, CD35, and stained weakly with CD79a. Fascin and CD23 showed only a weak and focal staining pattern. Bcl-2 decorated large centroblasts and small reactive T-cells. The tumor bulk was negative for actin, EMA, cytokeratins, vimentin, desmin, and factor XIIIa. The proliferative index was rather low; MIB-1 mainly decorated large centroblasts. No monoclonal rearrangement of IgH genes was detected. Epstein-Barr virus was not identified. Electron microscopy revealed typical features of FDCs intermingled with germinal center cells. Such cases may represent a diagnostic pitfall, as FDC overgrowth can mask FL and give the neoplasm the appearance of FDC sarcoma/tumor. We believe that, in both cases, the FDC proliferation had a reactive character.

Neoplastic cells do not carry bcl2-JH rearrangements detected in a subset of primary cutaneous follicle center B-cell lymphomas

Whether primary cutaneous follicular lymphoma (PCFL) may or not represent a cutaneous equivalent to nodal follicular lymphoma (FL) is not determined. We have therefore investigated a series of PCFL to determine if tumoral cells carry or not the t(14;18)(q32;q21) translocation, a cytogenetic hallmark of nodal FL. Thirty cases of PFCL were selected according to the criteria of both the European Organisation for Research and Treatment of Cancer and the World Health Organization with 21 cases classified as grade 1 or 2 and 9 cases as grade 3. First, cutaneous tumors were studied by PCR for the amplification of bcl-2/JH rearrangements and by interphase fluorescence in situ hybridization using a dual color probe spanning t(14;18) breakpoints. Second, we tried to determine the origin of bcl2-JH-positive cells by a parallel bcl2-JH and immunoglobulin heavy chain gene amplification of blood mononuclear cells DNA and of DNA extracted from single microdissected B cells. Bcl2-JH rearrangements were amplified by PCR in skin of 9 of 30 (30%) patients with a similar-sized bcl2-JH rearrangement detected in the blood of 7 of these 9 cases. No t(14;18) breakpoint was detected by interphase fluorescence in situ hybridization analysis of 11 bcl2-JH-negative and 5 bcl2-JH-positive PCFL in contrast with its detection in the secondary cutaneous FL and in the nodal FL cases. Single-cell/multigene analysis showed that no single monoclonal B cells of PCFL carried the bcl2-JH rearrangement. Bystander or nontumoral t(14;18)+ B cells emigrating from blood may account for the detection of bcl2-JH rearrangements within PCFL material. Our study also underlines the diagnostic value of interphase fluorescence in situ hybridization to discriminate between t(14;18)-negative PCFL and extracutaneous FL involving the skin.

IgV(H) and bcl6 somatic mutation analysis reveals the heterogeneity of cutaneous B-cell lymphoma, and indicates the presence of undisclosed local antigens

Our understanding of the ontology of B-cell lymphomas (BCL) has been improved by the study of mutational status of IgV(H) and bcl6 genes, but only a few cases of cutaneous BCL have been examined for this status. We analyzed IgV(H) and bcl6 somatic mutations in 10 cutaneous BCL, classified as follicular (three primary and one secondary), primary marginal zone (two cases), and diffuse large BCL (three primary and one secondary). We observed a lower rate (<2%) of IgV(H) mutation in all marginal zone lymphomas, and a preferential usage of V(H)2-70 (one primary follicular and two primary diffuse large BCL). Fewer than expected replacement mutations in framework regions (FR) were observed in three primary follicular lymphomas (FLs) and in all diffuse large BCL, indicating a negative antigen selection pressure. Ongoing mutations were observed in eight of 10 cases. Only two primary FLs and two diffuse large BCL showed bcl6 somatic mutation. These data support the heterogeneous nature of the different cutaneous BCL, and specifically the distinction between cutaneous follicular and marginal zone lymphomas. The biased usage of V(H)2-70, the low rate of replacement mutation in the FR, and the presence of ongoing mutation imply that local antigens could modulate the growth of primary cutaneous BCL.

Chromosomal Aberration Patterns Differ in Subtypes of Primary Cutaneous B Cell Lymphomas

The diagnostic and prognostic importance of recurrent chromosomal aberrations in systemic B cell lymphoma is well documented. In contrast, limited data exist on genetic changes in primary cutaneous B cell lymphoma. In this study we investigated chromosomal aberration patterns in two types of primary cutaneous B cell lymphoma with a different clinical behavior. Twenty-two primary cutaneous B cell lymphomas, including nine follicle center cell lymphomas and 13 large B cell lymphomas of the leg, were analyzed by comparative genomic hybridization and in part by fluorescence in situ hybridization. The most frequent imbalances detectable were gains in 18q (eight of 22), 1q (six of 22), 7 (six of 22), 12q (six of 22), or Xp (four of 22), and losses in 6q (four of 22). In contrast to large B cell lymphomas of the leg, primary cutaneous follicle center cell lymphomas had fewer imbalances and lacked translocations affecting the IGH locus. Gains in 18q (eight of 13) and losses in 6q (four of 13) as well as breakpoints within the IGH locus (six of 11) were restricted to the large B cell lymphomas of the leg subtype. Translocation t(14; 18) was excluded in 16 primary cutaneous B cell lymphomas of both subtypes that were studied by fluorescence in situ hybridization. These results suggest that primary cutaneous follicle center cell lymphoma and large B cell lymphoma of the leg are characterized by different chromosomal aberration patterns, which in part might determine the different clinical course of these malignancies.

Differential diagnosis of cutaneous infiltrates of B lymphocytes with follicular growth pattern

The differential diagnosis of cutaneous B-cell infiltrates with follicular pattern of growth is one of the most vexing problems in dermatopathology. In this study we focused on histopathologic, immunophenotypic, and molecular differential diagnostic criteria between Borrelia burgdorferi (Bb)-associated lymphocytoma cutis (LC), primary cutaneous follicle center cell lymphoma (FCCL), and primary cutaneous marginal zone lymphoma (MZL) with reactive germinal centers (GCs). A total of 47 patients were included in the study, including 12 cases of LC (M:F = 2:1; mean age: 38.0; median: 31; range: 9-75), 29 cases of FCCL (M:F = 1.2:1; mean age: 57.5; median: 57; range: 24-97), and 6 cases of MZL (M:F = 1:1; mean age: 63.8; median: 67.5; range: 38-86). In all cases complete phenotypic data were available. In addition, the IgH gene rearrangement and the t(14;18) were analyzed using the polymerase chain reaction technique (PCR) in 41 (FCCL = 27, LC = 10, MZL = 4) and 18 cases (FCCL = 15, LC = 2, MZL = 1), respectively. Histology revealed in all cases of FCCL one or more atypical feature of the follicles including the lack of or a reduced mantle zone, lack of polarization, tendency to confluence, and absence of tingible body macrophages. In most cases of Bb-associated LC, the GCs were devoid of mantle zone, lacked polarization, and revealed tendency to confluence as well, but all cases showed the presence of several tingible body macrophages. In MZL, follicles showed typical features of reactive GCs. Immunohistology revealed a reduced proliferative activity of neoplastic follicles as detected by MIB-1 antibody in 23 of 29 cases of FCCL (79.3%), but only in 1 case of LC (8.3%). Proliferation of the GCs was normal in all cases of MZL. Positivity for CD10 and/or Bcl-6 was found in small clusters outside the follicles in 19 cases of FCCL (65.5%), and in 3 cases of LC (25%), but in no case of MZL. The intensity of CD10 staining on follicular cells on average was stronger in cases of FCCL, but overlapping features could be observed. Finally, staining for Bcl-2 protein was consistently negative on GC cells in cases of LC and MZL, and was positive on a variable proportion of the cells in 8 cases of FCCL (28.6%). Molecular analyses showed no evidence of the t(14;18) in all cases tested. Analysis of the IgH gene rearrangement revealed a monoclonal pattern in 1 of 10 cases of LC (10%), 14 of 27 cases of FCCL (51.9%), and 2 of 4 cases of MZL (50%) tested. In summary, Bb-associated LC and FCCL show sometimes overlapping histopathologic, immunohistochemical, and molecular features, whereas follicles in MZL show clear-cut aspects of reactive GCs. Absence of tingible body macrophages within follicles, reduced proliferation of the follicles as detected by immunohistology, presence of positivity for Bcl-2 protein within follicular cells, and monoclonality by PCR are the main criteria suggestive of malignancy. Diagnosis of cutaneous infiltrates of B lymphocytes with follicular growth pattern should be achieved by integration of clinical data with histopathologic, immunohistochemical, and molecular features of the lesions.

Cutaneous B-cell lymphoma: pathological spectrum and clinical outcome in 51 consecutive patients

The clinical behavior and optimal treatment of patients presenting with skin infiltration by B-cell lymphoma have not been established. To clarify this we assessed the clinical and laboratory features of 51 patients presenting with cutaneous infiltration by B-cell lymphoma. Follow-up data was available for 46 patients with a median age of 68 years (range 16-89 years) and a median follow-up of 32.5 months (range 5-123 months). Thirty-three of 51 (65%) patients had diffuse large B-cell lymphoma (DLBCL), and 15/51 (29%) had marginal zone lymphoma (MZL). The remaining 3 patients had follicular lymphoma, CLL, and post-transplant lymphoproliferative disease. Of the 33 patients with DLBCL, follow-up was available in 29; 24/29 (83%) had primary cutaneous disease, which was unifocal in 17/24 (71%). Following treatment, 8/24 (33%) of the primary cases relapsed. Of the 8 who relapsed, 7 had received local forms of treatment only. Follow-up data was available in 14/15 patients with MZL. 11/14 (79%) had primary cutaneous disease, which was unifocal in 8 (73%). Following treatment, 4 of these cases relapsed (36%); all had received local therapy only. It is evident from this study that a significant proportion ( reverse similar 20%) of patients who present with cutaneous infiltration by B-cell lymphoma have systemic disease. Staging is therefore mandatory in these patients. Approximately 1/3 patients with primary cutaneous DLBCL or MZL ultimately relapse, and relapse rates appear higher in those patients receiving local therapy only. Systemic or combined modality therapy may therefore be the most appropriate treatment at presentation. This should be assessed prospectively in randomized trials.

Extranodal follicular lymphoma: a clinicopathological and genetic analysis of 15 cases arising at non-cutaneous extranodal sites

AIMS

Recent studies of primary cutaneous follicular lymphoma suggest that it represents a clinicopathological entity distinct from nodal follicular lymphoma (FL). The purpose of this study was to determine if FL arising at other extranodal sites is more closely related to FL occurring in the skin or in lymph nodes.

METHODS AND RESULTS

Fifteen cases of non-cutaneous extranodal follicular lymphoma (ENFL) were identified from the Scotland and Newcastle Lymphoma Group (SNLG) database. All were stage 1E at presentation and involved the tonsil (n = 3), palate (n = 3), skeletal muscle (n = 2), ileum (n = 2), duodenum (n = 1), stomach (n = 1), thyroid gland (n = 1), submandibular gland (n = 1) and fallopian tube (n = 1). Polymerase chain reaction for t(14;18) using primers to the major breakpoint cluster region was performed on 14 cases of ENFL and the incidence of the translocation compared with that found in 16 cases of stage 1 nodal FL. Clinical and follow-up data were obtained from the SNLG database for the 15 cases of ENFL and 87 cases of stage 1 nodal FL, and a comparison of outcomes made. Only 2/14 cases of ENFL had detectable t(14;18) compared with 9/16 stage 1 nodal FL (P < 0.01). Freedom from progression and disease-specific survival was similar for the 15 cases of ENFL and 87 cases of stage 1 nodal FL. However, 13/15 patients with ENFL were disease free at the end of follow-up compared with 49/87 stage 1 nodal FL (P < 0.02).

CONCLUSIONS

The low incidence of t(14;18) and favourable outcome encountered in ENFL in this study is similar to that previously found for primary cutaneous FL. These results support the concept of a subtype of FL lacking t(14;18) involving the major breakpoint cluster region, and with a propensity to arise at extranodal sites. Despite a high relapse rate, patients with ENFL are more likely to achieve complete remission and may ultimately have a more favourable long-term prognosis than those with equivalent nodal disease.

Primary Cutaneous Diffuse Large B-cell Lymphoma

Classification and subdivision of primary cutaneous diffuse large B-cell lymphoma (PCDLBCL) are a matter of ongoing debate. In this study we assessed the morphologic, immunophenotypic, and clinical features of 30 cases of PCDLBCL identified during a review of all primary cutaneous B-cell lymphomas in the Scotland and Newcastle Lymphoma Group database. We also determined the number of cases harboring t(14;18) using a polymerase chain reaction and primers to the major breakpoint cluster region. The effect on prognosis of a variety of clinical and pathologic factors was assessed for the group of 30 PCDLBCL and the 5-year disease-specific survival (DSS) of this cohort compared with that of 195 cases of stage I diffuse large B-cell lymphoma arising primarily in lymph nodes, also identified from within the Scotland and Newcastle Lymphoma Group database. Location on the leg was the only independent prognostic factor for determining outcome in PCDLBCL (67% 5-year DSS compared with 100% for the upper body; P = 0.0047). The presence of multiple lesions, involvement of more than one body site, and expression or not of CD10, bcl-2, bcl-6, and CD10 and bcl-6, had no effect on survival. Compared with cases arising above the waist, those on the leg were more often female, were of an older age, and had a significantly higher incidence of bcl-2 expression (P = 0.002) as well as the aforementioned poorer prognosis. They also showed more frequent co-expression of CD10 and bcl-6, supporting a follicle center cell origin for some, but this difference was not statistically significant. Although there was no significant difference in the 5-year DSS between the group of PCDLBCL and the cases of stage I nodal diffuse large B-cell lymphoma (88% 5-year DSS vs. 78%; P = 0.06), the latter were generally treated with more aggressive therapy. Moreover, a significant difference in 5-year DSS was seen when the nodal DLBCLs were compared with PCDLBCLs arising above the waist (78% vs. 100% respectively; P = 0.0135). These results support the current EORTC approach of subdividing PCLBCL on the basis of site to produce prognostically relevant groupings.

Bcl-2, Bcl-6 and CD10 expression in cutaneous B-cell lymphoma: further support for a follicle centre cell origin and differential diagnostic significance

BACKGROUND

Primary cutaneous follicle centre cell lymphomas (PCFCCLs) are the most common type of cutaneous B-cell lymphoma. There is ongoing discussion on the origin of the neoplastic B cells in these PCFCCLs, and consequently on their relation to the groups of primary cutaneous marginal zone B-cell lymphomas (PCMZLs) and nodal follicular lymphomas.

OBJECTIVES

To define better the neoplastic B cells in PCFCCLs, and to find out if differences in the expression of the antiapoptopic protein Bcl-2, and Bcl-6 and CD10, molecules which are normally expressed by the neoplastic B cells in nodal follicular lymphomas, might have diagnostic or prognostic significance in cutaneous B-cell lymphoproliferative disorders.

METHODS

Pretreatment biopsies of well-defined groups of PCFCCL (n = 24), PCMZL (n = 14), primary cutaneous large B-cell lymphoma of the leg (PCLBCL-leg; n = 19), secondary cutaneous follicular lymphoma (n = 3) and cutaneous pseudo-B-cell lymphoma (n = 6) were investigated by immunohistochemistry for expression of Bcl-2, Bcl-6 and CD10.

RESULTS

The PCFCCLs consistently expressed Bcl-6, whereas CD10 and Bcl-2 were expressed in only one and two of 24 cases, respectively. In contrast, PCMZLs were always negative for Bcl-6 and CD10, but were Bcl-2 positive, whereas skin and lymph node localizations of secondary cutaneous follicular lymphomas consistently expressed all of Bcl-2, Bcl-6 and CD10. Reactive follicle centre cells in pseudo-B-cell lymphomas expressed Bcl-6 (six of six cases) and CD10 (five of six cases), but not Bcl-2. PCLBCL-leg was Bcl-6 positive and CD10 negative in all cases, irrespective of clinical outcome, and strongly expressed Bcl-2 protein in all but two cases.

CONCLUSIONS

The results of the present study provide further support for the follicle centre cell origin of both PCFCCL and PCLBCL-leg, and indicate that staining for Bcl-2, Bcl-6 and CD10 can serve as an important adjunct in the differential diagnosis of cutaneous B-cell lymphoproliferative disorders.

Lymphoma of the skin

This chapter describes the various ways in which the non-Hodgkin's lymphomas can involve the skin, how these diseases should be assessed, standard treatments available in 2002, and new directions in research. The goal of the session is to succinctly review recent developments in lymphoma classification and treatment as they apply to the unique aspects of lymphoma when manifest in the skin. In Section I, Dr. Eric Hsi reviews the special characteristics of the lymphomas seen when they proliferate in the skin and the application of the new World Health Organization classification system to the cutaneous lymphomas, emphasizing the unique challenges of recognizing and correctly classifying these diseases. He summarizes the evidence in favor of including the skin lymphomas in the overall lymphoma classification scheme and concludes with a practical description of the specific skin lymphoma entities. In Section II, Dr. Joseph Connors describes the current optimal treatment of the B-cell lymphomas when they present in or metastasize to the skin. Building on the classification scheme described by Dr. Hsi, Dr. Connors outlines a treatment approach based on current understanding of pathophysiology of these diseases and application of each of the effective modalities available for cutaneous lymphoma including radiation, chemotherapy, and immunotherapy. In Section III, Dr. Francine Foss concludes the session with a discussion of the different T-cell lymphomas that start in or spread to the skin concentrating on mycosis fungoides, cutaneous anaplastic large cell lymphoma and peripheral T-cell lymphoma. She includes comments on the newer anti-T-cell chemo- and immuno-therapeutics focusing on agents and techniques specific for cutaneous T-cell lymphomas.

Primary and secondary cutaneous diffuse large B-cell lymphomas: a multiparameter analysis of 25 cases including fluorescence in situ hybridization for t(14;18) translocation

Although primary cutaneous diffuse large B-cell lymphomas (DLBCLs) except for those of the leg are grouped together with primary cutaneous follicle center cell lymphoma in the European Organization for Research and Treatment of Cancer classification of primary cutaneous lymphomas, they typically lack the usual phenotypic profile of follicular lymphoma. Whether they are truly of follicular center cell origin, have a molecular pathogenesis similar to nodal follicular lymphoma, or have any biologic features that distinguish them from secondary DLBCL involving skin remains uncertain. To address these issues, a retrospective multiparameter study of 25 patients including clinical, histologic, immunophenotypic, and cytogenetic analyses was performed. A classic CD10+, bcl-6+ follicular center cell profile was found in 10 (40%) cutaneous DLBCL (2 of 11 primary, 5 of 8 secondary, 3 of 6 unclassified) with bcl-2 expression seen only in the nonprimary cases. Of the remaining cases, 14 cases (56%) were CD10-, bcl-6+, bcl-2+/- (9 primary) and one case (4%) was CD10-, bcl-6-, bcl-2+ (0 primary). Fluorescence in situ hybridization analysis showed a t(14;18) in 0 of 9 primary and 3 of 5 secondary cases. Primary cases were frequently found in the head/neck region, whereas secondary cases were more common on the trunk and extremities. Patients with primary disease were all alive, usually having received only local therapy, at a median follow-up of 19 months. Most secondary cases were treated with chemotherapy with only one untreated patient dead of disease at a median follow-up of 5 months. Primary cutaneous DLBCLs therefore appear to be distinctive as they have fewer features of follicular lymphoma than do secondary cases. Nevertheless, some appear to be of follicular center cell origin, even though they probably have a different molecular pathogenesis than most nodal follicular lymphomas.

World Health Organization classification of hematopoietic and lymphoid tissues: implications for dermatology

The new World Health Organization (WHO) classification of hematopoietic and lymphoid malignancy represents the first worldwide consensus document on the classification of lymphoma/leukemia. Its aim is to supercede all existing classification systems, including the Revised European American Classification (REAL), and the organ-based classification of cutaneous lymphoma proposed in 1997 by the European Organization for Research and Treatment of Cancer (EORTC) cutaneous lymphoma project group. This article compares the REAL, EORTC, and WHO classifications with particular reference to cutaneous lymphoma. It identifies those entities that have been adopted from the EORTC classification, and illustrates important new entities in the category of cytotoxic T-/NK-cell lymphomas that characteristically present in the skin or subcutaneous tissue. However, WHO is not an organ-based classification and some categories (eg follicular B-cell lymphoma and peripheral T-cell lymphoma) include both cutaneous and systemic diseases, and these may have very different prognoses. It is, therefore, important that cancer registries are capable of recording sites of involvement for both B- and T-cell lymphomas so that the incidence and prognosis of cutaneous lymphomas can be established from national data sets in future years.

The t(14;18) and bcl-2 expression are present in a subset of primary cutaneous follicular lymphoma: association with lower grade

According to the European Organization for Research and Treatment of Cancer classification, primary cutaneous follicle center cell lymphoma is not associated with the t(14;18)(q32;q21) and only rarely expresses bcl-2 protein. To further investigate this issue, we evaluated a series of 20 patients (14 men, 6 women) with primary cutaneous follicular lymphoma (PCFL). The presenting skin lesion was located in the head and neck region in 16 of 20 patients. Most cases were grade 2 (6/20) or grade 3 (13/20), and all had a follicular architecture. Immunohistochemical analysis demonstrated bcl-2 expression in 8 cases (40%), and expression was inversely related to the grade. Of 7 grade 1 or 2 cases, 5 (71%) were positive, whereas only 3 (23%) of 13 grade 3 cases were positive for bcl-2. Clonal immunoglobulin heavy chain gene rearrangements were detected in 9 (45%) of 20 cases. In 4 (20%) of 20 cases, we identified the major breakpoint of the t(14;18) by polymerase chain reaction, 3 of which were grade 1 or 2. We conclude that bcl-2 protein expression and the t(14;18) are present in a subset of PCFL, particularly in lower grade cases.

Comparative genomic hybridization analysis of primary cutaneous B-cell lymphomas: identification of common genomic alterations in disease pathogenesis

To investigate genetic alterations in primary cutaneous B-cell lymphomas (PCBCLs), we have analyzed 29 cases of PCBCL. Comparative genomic hybridization showed chromosome imbalances (CIs) in 12 cases (41%). The mean number of CIs per sample was 2.05 +/- 2.97, with gains (1.48 +/- 2.38) more frequent than losses (0.56 +/- 1.40). The common regions of gains were 18/18q (50%), 7/7p (42%), 3/3q (33%), 20 (33%), 1p (25%), 12/12q (25%), and 13/13q (25%), whereas loss of 6q was frequent (42%). Among the different subsets of PCBCLs, CI was seen in 50% of diffuse large-cell lymphomas (DLCLs), 33% of marginal zone lymphomas, and 8% of follicle center cell lymphomas and unclassified lymphomas. A similar pattern of CI was observed in these lymphomas, but loss of 6q and gains of 3/3q were present only in DLCLs. Microarray-based genomic analysis of four DLCL cases identified oncogene gains of SAS/CDK4 (12q13.3) in three cases and MYCL1 (1p34.3), MYC (8q24), FGFR2 (10q26), BCL2 (18q21.3), CSE1L (20q13), and PDGFB (22q12-13) in two cases, whereas losses of AKT1 (14q32.3), IGFR1 (15q25-26), and JUNB (19p13.2) were identified in three cases, and losses of FGR (1p36), ESR (6q25.1), ABL1 (9q34.1), TOP2A (17q21-22), ERBB2 (17q21.2), CCNE1 (19q13.1), and BCR (22q11) were each identified in two cases. In addition, real-time-polymerase chain reaction detected amplification of BCL2 in 5 of 29 cases. These findings suggest that there are complex but consistent genetic alterations associated with the pathogenesis of PCBCLs.

Inactivation of tumor suppressor genes p15(INK4b) and p16(INK4a) in primary cutaneous B cell lymphoma

Primary cutaneous B cell lymphomas represent a distinct group of lymphoproliferative disorders that can be distinguished from systemic lymphoma by their good response to local treatment and favorable prognosis. In systemic B cell lymphoma, inactivation of p15(INK4b) and p16(INK4a) is frequently observed and may be associated with a poor prognosis. There have been no comprehensive studies in primary cutaneous B cell lymphomas, however. Mechanisms of p15/p16 inactivation include loss of heterozygosity, homozygous deletion, promotor region hypermethylation, and point mutation. We analyzed DNA from 36 cases of primary cutaneous B cell lymphomas, four systemic B cell lymphomas, and six benign B cell lymphoproliferative infiltrates for abnormalities of p15 and p16 using microsatellite markers for 9p21, methylation specific polymerase chain reaction, and polymerase chain reaction/single stranded conformational polymorphism analysis with exon specific primers. Expression of both p15 and p16 protein was assessed by immunohistochemistry. Loss of heterozygosity at 9p21 was identified in 2 out of 36 primary cutaneous B cell lymphomas. Hypermethylation of p15 and p16 promotor regions was identified in 8 of 35 (23%) and 15 of 35 (43%) cases, respectively. In two cases p16 hypermethylation was identified in recurrent disease but not in the initial tumor. No point mutations were identified. In seven patients, however, a polymorphism was observed in exon 3 of the p16 gene. In primary cutaneous B cell lymphomas with allelic loss or promotor hypermethylation of either p15 or p16, loss of expression in tumor cells was identified in 5 of 8 and 9 of 10 cases, respectively. Our findings suggest that p15(INK4b) and p16(INK4a) biallelic gene abnormalities are common in primary cutaneous B cell lymphomas, most frequently as a result of promotor hypermethylation. The presence of abnormalities in recurrent disease in some cases suggests that inactivation of p15 and p16 may be involved in disease progression.

Primary cutaneous follicular lymphoma: a clinicopathologic and molecular study of 16 cases in support of a distinct entity

Primary cutaneous B-cell lymphomas displaying a prominent follicular growth pattern are rare and remain poorly defined, particularly in terms of the frequency of detection of t(14;18) and whether or not, as a group, they represent an entity distinct from follicular lymphoma arising in lymph nodes. The morphologic, immunophenotypic, and clinical features of 16 cases of primary cutaneous follicular lymphoma, identified during a review of all PCBCL in the Scotland and Newcastle Lymphoma Group database, were studied and the number of cases harboring t(14;18) assessed by polymerase chain reaction using primers to the major breakpoint cluster region. Comparisons were made with stage I follicular lymphoma arising in lymph nodes and follicular lymphoma secondarily involving the skin. All cases of primary cutaneous follicular lymphoma had undergone thorough staging, including physical examination and CT scans of chest and abdomen, with 15 of 16 cases also having bone marrow aspiration and/or trephine performed. The morphology and immunophenotype of the lesions were similar to that expected in lymph nodes. All cases displayed a follicular architecture complete with follicular dendritic cell networks and comprised an admixture of CD10 and/or bcl-6-positive neoplastic centrocytes and centroblasts with 13 of 16 cases also expressing bcl-2 protein. None harbored t(14;18), a significantly different finding compared with cases of stage I nodal follicular lymphoma (p <0.001) and secondary cutaneous follicular lymphoma (p <0.039). Relapses occurred in five of 15 patients with a median time to first relapse of 20 months (range 1-73 months; mean 27.2 months). These were multiple in two patients and involved extracutaneous sites in two patients. The propensity for relapse was similar to that in a comparative cohort of stage I nodal follicular lymphoma, but the group of primary cutaneous follicular lymphoma were significantly more likely to attain complete remission; all cases of primary cutaneous follicular lymphoma were in complete remission when last seen compared with 49 of 87 patients with stage I nodal follicular lymphoma (p <0.005). No lymphoma-related deaths were encountered in 15 cases with a mean follow-up >60 months (range 5-119 months). These results support the concept of a subtype of follicular lymphoma lacking t(14;18) involving the major breakpoint cluster region, and with a propensity to arise in the skin. Despite a high relapse rate patients with primary cutaneous follicular lymphoma are more likely to achieve complete remission and may ultimately have a more favorable long-term prognosis than those with equivalent nodal disease.

Primary cutaneous follicular lymphoma: an assessment of clinical, histopathologic, immunophenotypic, and molecular features

PURPOSE

Unlike nodal follicular lymphoma (NFL), Primary cutaneous follicular lymphomas (PCFLs) rarely express Bcl-2 protein or t(14;18)(q32;q21) (Bcl-2/IgH). The aim of this study was to further characterize PCFL in a large series from North America.

PATIENTS AND METHODS

Clinical data and archival formalin-fixed, paraffin-embedded tissue were obtained from 32 patients. PCFL was defined as follicular lymphoma limited to the skin at the time of diagnosis and within the first 6 months after diagnosis. Specimens were analyzed for the expression of CD3, CD10, CD20, Bcl-2, and Bcl-6 proteins by immunohistochemistry as well as for the presence of t(14;18)(q32;q21) by polymerase chain reaction.

RESULTS

The male-to-female ratio was 1.5:1, with a median age of 60 years. Twenty-four patients had lesions on the head and neck, five had lesions on the trunk, and three had lesions on both head and trunk. Follow-up data were available in all cases, with a mean length of 35.8 months. The majority of the patients were treated with radiation therapy. All patients were alive at last follow-up except one. Recurrence was noted in seven patients (22%), after a mean disease-free survival time of 17.7 months. CD10 and Bcl-6 expression were seen in 29 (91%) of 32 and 31 (97%) of 32 cases, respectively. Bcl-2 expression was noted in 13 (41%) of 32 cases. PCR results for t(14;18)(q32;q21) were positive in 11 (34%) of 32 patients and showed correlation with Bcl-2 protein expression. The sequencing of the t(14;18)(q32;q21) amplicons confirmed unique breakpoints in each of the seven tested cases. Comparison between the Bcl-2 and/or t(14;18)(q32;q21)-positive and t(14;18)(q32;q21)-negative cases revealed no significant difference in age, site, clinical course, or outcome.

CONCLUSION

We demonstrated Bcl-2 protein expression and t(14;18)(q32;q21) in a significant minority of cases, suggesting a relationship with NFL. It remains to be seen whether, on longer follow-up, there is any clinical difference in cases with and without t(14;18)(q32;q21).

Cutaneous presentation of follicular lymphomas

The description of primary cutaneous follicular lymphoma has raised interest in the differential diagnosis of this versus disseminated follicular lymphoma involving the skin. We report here on four cases of Stage IV follicular lymphoma, diagnosed in skin biopsy, in which cutaneous lesion was the most noticeable feature of clinical presentation. In all cases, the morphological features were superimposed over typical nodal follicular lymphoma. Apart from classic B-cell markers, they were characterized by CD10 and bcl6 positivity, markers of follicle germinal center cells; and bcl2 expression, with a corresponding t(14;18) translocation in three of three cases examined. In all four cases, bone marrow study and clinical staging revealed disease that had disseminated since diagnosis. Follow-up showed relapsing cutaneous and nodal disease in two cases. The only difference observed with a control group of 10 cases of primary cutaneous follicular lymphoma was the absence in this group of t(14; 18). Disseminated classical follicular lymphoma has to be considered in the differential diagnosis of follicular lymphoma presenting in the skin. This series of cases suggests that the presence of t(14;18) could imply the existence of disease that has disseminated beyond the skin and that cases harboring this translocation could be candidates for systemic polychemotherapy.