T-cell-rich B-cell lymphoma presenting in skin. A clinicopathologic analysis of six cases

Primary Cutaneous T-Cell/Histiocyte-Rich B-Cell Lymphoma: A Case Report and Literature Review

T-cell/histiocyte-rich large B-cell lymphoma (THRLBCL) is a lymphoproliferative disorder in which the majority of cells are reactive T cells with only a minor population of neoplastic large B cells. THRLBCL is a very rare lymphoma, and most cases are nodal THRLBCL; an extranodal case of THRLBCL presenting primarily on the skin is an extremely rare occurrence with only a few cases reported in the literature. Here, we report a case of a primary cutaneous THRLBCL in a 41-year-old Saudi male who presented unusually with multiple skin lesions. He was successfully treated with electron beam radiotherapy and had a complete resolution with no recurrence as of his 24-month follow-up.

Kappa and lambda immunohistochemistry and in situ hybridization in the evaluation of atypical cutaneous lymphoid infiltrates

BACKGROUND

Atypical cutaneous lymphoid infiltrates are challenging lesions in dermatopathology. We present a summary of the literature regarding kappa and lambda immunohistochemistry (IHC) and in situ hybridization (ISH) in the evaluation of atypical cutaneous or mucosal lymphoid infiltrates.

METHODS

Relevant articles from 1967 to 2018 in the English language were identified and summarized. In the absence of larger studies, case series of n ≥ 3 were included.

RESULTS

Sixty-three articles assessing kappa and lambda IHC and/or ISH were identified. Most focused on marginal zone lymphomas. Other lymphomas included follicle center lymphoma, diffuse large B-cell lymphoma, chronic lymphocytic leukemia/small lymphocytic lymphoma, mantle cell lymphoma, lymphoplasmacytic lymphoma, plasmablastic lymphoma, multiple myeloma, monoclonal gammopathy of undetermined significance, and polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, skin changes (POEMS). Non-neoplastic lesions included reactive lymphoid hyperplasia, cutaneous plasmacytosis, connective tissue disease, IgG4-related disease, acrodermatitis chronic atrophicans, Zoon balanitis, dermatitides, and infiltrates around epithelial dysplasias/neoplasias.

CONCLUSION

Kappa and lambda IHC and ISH are useful tools in the evaluation of cutaneous B-cell lymphomas and plasma cell neoplasms. The literature supports that the detection of light-chain restriction by IHC and ISH is one of the most useful findings in the differential diagnosis of reactive lymphoid hyperplasia vs B-cell lymphoma with plasmacytic differentiation.

B-cell Lymphofollicular Infiltrates in Mycosis Fungoides

Aims and background

The histopathological picture of mycosis fungoides can be characterized by heavy reactive infiltrates. These are rarely composed of B lymphocytes with formation of reactive follicles.

Methods and study design

We collected three cases of mycosis fungoides with a reactive B-cell lymphofollicular reaction at the bottom of the epidermotropic infiltrate.

Results

Case 1 showed flat lesions (patches) with a CD4+ neoplastic phenotype; case 2 presented infiltrated lesions (plaques) with a CD8+ immonophenotype; case 3 was characterized by nodular lesions (tumors) with a CD4+ neoplastic component. In all three cases, no clonal gene rearrangement was found with the polymerase chain reaction technique.

Conclusions

Among the protean clinicopathological features which mycosis fungoides can show, we underline that a B-cell lymphofollicular component can be encountered at the base of the epidermotropic infiltrate even in clinically flat (“patchy”) lesions.

Cutaneous T-cell/histiocyte-rich B-cell lymphoma: a case report and review of the literature

BACKGROUND

T-cell/histiocyte-rich large B-cell lymphoma (THRLBCL) primarily presenting on the skin is an extremely rare entity with only sporadic cases reported in the literature.

METHODS

We here report an extraordinary case of primary cutaneous THRLBCL with self-healing and 24 months of follow-up.

RESULTS

The lesion was a dermohypodermal/subcutaneous circumscribed ulcerated nodosity. Histological examination with immunohistochemical, molecular analysis and comparative genomic hybridization were performed. A complete staging was negative for secondary involvement.

CONCLUSION

Our case is remarkable because it is the second well-documented primary cutaneous THRLBCL in which we observed a complete self-regression of skin lesions without recurrences or dissemination of the disease. According to the literature, we highlight that the tumoral microenvironment, in our case, could play a relevant role in stopping lymphoma growth. Furthermore, this case supports the observation that THRLBCL primarily presenting on the skin shows an overall good prognosis.

Characteristics of cutaneous marginal zone lymphomas with marked plasmacytic differentiation and a T cell-rich background

Primary cutaneous marginal zone lymphoma (MZL) is a common B-cell lymphoma of skin and is characterized by an infiltrate of neoplastic marginal zone B cells typically within the marginal zones of reactive lymphoid follicles and the interfollicular region. However, in our experience, many cases have underemphasized features such as marked plasmacytic differentiation and/or a prominent T-cell component, which may obscure the neoplastic B cells and lead to misdiagnosis. We wanted to draw attention to these features and have studied 15 cases of MZL with marked plasmacytic differentiation, 10 of which had numerous T cells, some with cytologic atypia, and few B cells in the interfollicular region. Plasma cells were monotypic in all cases by in situ hybridization. By polymerase chain reaction, 6 of 8 T cell-rich cases had an IGH gene rearrangement, and none were clonal for T-cell receptor gene. We discuss the terminology, morphologic features, molecular profile, behavior, and differential diagnosis of cutaneous MZL.

Primary cutaneous B-cell lymphoma: classification and treatment

PURPOSE OF REVIEW

There has been confusion and debate regarding the definition, terminology, and optimal treatment of the different types of primary cutaneous B-cell lymphomas. This review presents the new World Health Organization-European Organization for the Research and Treatment of Cancer classification for cutaneous lymphomas; describes clinicopathologic, immunophenotypic, and genetic features of the different types of cutaneous B-cell lymphomas in this classification; and discusses current views on treatment of these lymphomas.

RECENT FINDINGS

The three main types of cutaneous B-cell lymphomas in this new classification are primary cutaneous marginal zone B-cell lymphoma, primary cutaneous follicle center lymphoma, and primary cutaneous large B-cell lymphoma (leg type). Primary cutaneous marginal zone B-cell and primary cutaneous follicle center lymphoma are indolent types with an excellent prognosis that should be treated primarily with nonaggressive therapies. Primary cutaneous large B-cell lymphoma (leg type) is an aggressive lymphoma that should be treated primarily with aggressive chemotherapy.

SUMMARY

The World Health Organization-European Organization for the Research and Treatment of Cancer classification will contribute to uniform diagnosis, management, and treatment of patients with cutaneous B-cell lymphoma and will prevent patients with indolent types of the disease from being treated inappropriately with systemic chemotherapy.

Follicular mycosis fungoides mimicking a cutaneous B-cell lymphoproliferative disorder

Follicular mycosis fungoides (MF) is an uncommon histological variant of MF characterized by infiltrates of atypical lymphocytes around and within the epithelium of the hair follicles (folliculotropism). Here we report a patient with rapidly progressive follicular MF on the face, associated with concurrent typical MF lesions elsewhere. The histology was unusual, as apart from dense lymphoid infiltrates showing folliculotropism and epidermotropism, there was a prominent B-cell component with germinal centres, leading to an initial diagnosis of cutaneous B-cell lymphoma. The final diagnosis of follicular MF was established on demonstration of clonal T-cell receptor gene arrangements and lack of clonality for heavy chain gene rearrangements. This case illustrates a variant of MF that has a more rapid progression than the otherwise indolent course of classical MF over many years, and the diagnostic pitfalls, whereby the histology can mimic a B-cell proliferative disorder.

Disseminated Cutaneous B-cell Lymphoma Mimicking Pseudolymphoma over a Period of Six Years

We describe a patient with a disseminated nodular cutaneous B-cell lymphoma, whose diagnosis was finally made after a long series of biopsies in different institutions in Europe and the United States. The differential diagnosis between lymphoma and pseudolymphoma was the recurrent problem throughout the patient's history because histologic and immunophenotypic criteria alone were not sufficient for differentiation. Molecular biology inconsistently detected clonal immunoglobulin rearrangements, which proves that careful clinicopathologic correlation remains mandatory. In contrast to a claimed "high-grade" malignant histology, this lymphoma responded with remission to PUVA therapy combined with intralesional corticosteroids, which is uncommon in the management of cutaneous B-lymphomas.

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 cutaneous T-cell-rich B-cell lymphoma in a zosteriform distribution associated with Epstein-Barr virus infection

T-cell-rich B-cell lymphoma (TRBL) is a lately recognized B-cell lymphoma variant characterized by a minor population of neoplastic B cells existing in a background of predominant polyclonal T cells. We report an 86-year-old man with primary cutaneous TRBL associated with Epstein-Barr (EB) virus infection. Clinically, palpable scaly erythemas were distributed in a zosteriform pattern on the right abdomen. Histologically, massive cellular infiltrates were located in the upper- and mid-dermis. Higher magnification showed that the cellular infiltration was composed mainly of abnormal mononuclear, large lymphoid cells with clear cytoplasm and scattered mitoses and small lymphocytes, which represented in excess of 75% of all the infiltrating cells. Immunohistochemical staining revealed that the large cells were positive for the B cell marker, CD20, but negative for the T cell marker, CD3. On the other hand, the small cells were positive for CD3, but negative for CD20. Polymerase chain reaction (PCR) revealed EB virus DNA in the skin lesion. Primary cutaneous TRBL has only been reported in 15 cases worldwide. To our knowledge, this is the first case of primary cutaneous TRBL in a zosteriform distribution reported in the literature and the second case of primary cutaneous TRBL associated with the EB virus infection. We postulate that the EB virus may be a contributory pathogenetic event leading to monoclonal B-cell proliferation.

The value of molecular analysis by PCR in the diagnosis of cutaneous lymphocytic infiltrates

The diagnosis and classification of cutaneous lymphomas remain a challenge for the clinician and dermatopathologist. This diagnostic dilemma is mainly encountered in the distinction between an early malignant lymphoma and a benign reactive lymphocytic infiltrate (pseudolymphoma). Until the beginning of the 1980s, our diagnostic tools were limited to the clinical presentation, course, and histopathology in diagnosis and classification of lymphocytic infiltrates. Advances in immunology and, in particular, in molecular genetics with the introduction of the Southern blot technique and the polymerase chain reaction (PCR) have revolutionized the diagnosis of lymphocytic infiltrates by determination of clonality. In some series, more than 90% of cutaneous T-cell lymphomas have a clonal rearrangement of the T-cell receptor gamma-chain gene, as opposed to very low percentages of rearrangement in T-cell pseudolymphomas. However, the presence of clonality does not necessarily imply malignancy. Cases of pseudolymphomas, lichen planus and pityriasis lichenoides et varioliformis acuta were reported with clonal lymphocytic proliferations. Therefore, care should be exercised in the evaluation of the results of molecular analysis, and these should always be correlated with the clinical, histological and immunophenotypic picture to arrive at the correct diagnosis. It may be expected that the molecular methods for diagnosis of lymphocytic infiltrates will be improved and refined in future, and that sensitivity and specificity will increase.

Follicular mycosis fungoides. A histopathologic analysis of nine cases

BACKGROUND

The spectrum of mycosis fungoides is exceedingly broad. Many different variants have been described, based on both clinical appearance and histological pattern. A rare form which shows preferential infiltration of hair follicles by malignant lymphocytes is follicular mycosis fungoides.

METHODS

We reviewed our experience with nine cases of follicular mycosis fungoides.

RESULTS

The unifying feature was infiltration of the hair follicle epithelium by atypical lymphocytes causing varying degrees of damage to the hair follicles. In some specimens the lymphocytes displayed only minor atypia leading to a misinterpretation as pseudolymphoma. Gene rearrangement studies were particularly helpful for establishing a diagnosis of malignant lymphoma. Additionally, epidermotropism of lymphocytes, eosinophils and mucin deposition were present to varying degrees. Mucin makes the distinction from mycosis fungoides-associated follicular mucinosis difficult. We found both dermal mucin and a follicular mucinosis pattern present at different stages of disease in the same patient.

CONCLUSIONS

We suggest the term mycosis fungoides-associated follicular mucinosis should be replaced by follicular mycosis fungoides in future lymphoma classification schemes.

Cutaneous manifestations of lymphoma: a clinical guide based on the WHO classification. World Health Organization

Cutaneous lymphomas are a heterogeneous group of lymphomas that show variations in histology, immunophenotype, and prognosis. At the time of presentation, cutaneous lymphomas may be primary or may involve the skin as a secondary site of involvement. Primary cutaneous lymphomas, in many instances, are distinct from morphologically similar lymphomas arising in lymph nodes. Their natural history is often more indolent than nodal lymphomas, and for that reason, they often require different therapeutic approaches. A classification scheme should recognize those lymphomas that are unique to the skin, as well as those arising in other sites. The mode of presentation of a lymphoma is often an indication of underlying biological distinctions. However, organ-specific classification systems undermine communication among medical specialists. The World Health Organization classification of hematopoietic and lymphoid malignancies offers a comprehensive approach and proposes that lymphomas should be viewed as a list of individual diseases and that each disease can be defined by a constellation of morphological, biological, and clinical features. The current review will focus on the spectrum of primary and secondary cutaneous lymphomas, emphasizing those features of importance to the clinical oncologist.

Primary cutaneous T-cell-rich B-cell lymphoma: clinically distinct from its nodal counterpart?

The cases of two patients with Stage IE primary cutaneous T-cell-rich B-cell lymphoma (TCRBCL) are described. In both, the lesion showed a dense infiltrate by numerous small T lymphocytes with scattered histiocytes and large atypical B-lymphoid cells. Polymerase chain reaction assays demonstrated that the B cells were monoclonal, with immunoglobulin heavy-chain gene rearrangement. No clonal rearrangements of the T-cell receptor gamma gene were observed. Both patients were disease-free at 4 months and at 5 years after therapy, respectively. Although rare, primary cutaneous T-cell-rich B-cell lymphoma appears to have a better prognosis than its nodal counterpart, with or without skin involvement.

Primary cutaneous B-cell lymphoma: review and current concepts

PURPOSE

Primary cutaneous B-cell lymphoma (PCBCL) has only recently been recognized as a distinct clinical entity. With the advent of improved immunophenotyping and immunogenotyping, increasing numbers of PCBCL cases are being diagnosed. However, there is much confusion regarding the classification, treatment, and prognosis of these patients. The purpose of this article is to review and analyze the available data to provide the clinician with a concise summary of the diagnosis, prognosis, and treatment of PCBCL.

DESIGN

We conducted a thorough review of the medical literature on PCBCL, with a focus on classification, prognosis, and treatment trials.

RESULTS AND CONCLUSION

PCBCL is defined as a B-cell lymphoma originating in the skin. There is no evidence of extracutaneous disease at presentation and for 6 months after diagnosis, as assessed by adequate staging procedures. Currently, the European Organization for Research and Treatment of Cancer classification is the most concise disease classification scheme, dividing the subtypes of PCBCL by clinical behavior and histopathologic findings. Based on this classification, the most common subtype of PCBCL is follicular center cell lymphoma. PCBCL is generally an indolent form of lymphoma with a good prognosis. Although local cutaneous recurrences are observed in 25% to 68% of patients, dissemination to internal organs is rare. Five-year survival rates typically range from 89% to 96%. A specific subtype, large B-cell lymphoma of the leg, is noted to have a poorer prognosis, with a 5-year survival rate of 58%. Overly aggressive treatment of PCBCL has not been shown to improve survival or prevent relapse. The treatment of choice usually varies depending on the type of PCBCL, the body surface area, and the location of the involvement, as well as the age and general health condition of the patient. The majority of studies indicate that PCBCL is highly responsive to radiation therapy. Polychemotherapy should be reserved for involvement of noncontiguous anatomic sites or those with extracutaneous spread.

Primary cutaneous T-cell-rich B-cell lymphomas with flow cytometric immunophenotypic findings. Report of 3 cases and review of the literature

BACKGROUND

Primary cutaneous T-cell-rich B-cell lymphoma is a relatively rare entity that has been diagnosed most commonly using immunohistochemical and molecular techniques. Flow cytometric immunophenotyping (FCI) has not been described in this entity. We report the demonstration of B-cell monoclonality by FCI in 3 cases of primary cutaneous T-cell-rich B-cell lymphoma.

METHODS

Clinical and pathologic data were recorded for 3 cases of primary cutaneous T-cell-rich B-cell lymphoma. Immunohistochemical and FCI data were available in all cases; DNA analysis was performed in 1 case.

RESULTS

Flow cytometric immunophenotyping revealed a monoclonal B-cell population exclusively in the monocyte (large cell) region in all 3 cases. Immunohistochemistry confirmed the T-cell richness of the infiltrates within the cutaneous lymphomas; T cells accounted for 65% to greater than 90% of the cells within the infiltrates. DNA analysis by polymerase chain reaction in 1 case did not demonstrate a monoclonal rearrangement of the immunoglobulin heavy-chain gene.

CONCLUSIONS

Flow cytometric immunophenotyping in primary cutaneous T-cell-rich B-cell lymphoma may be useful in demonstrating monoclonality in these cases, especially if there is selective gating on the relatively small population of cells in the large cell region. The FCI data should be correlated with histology and immunohistochemistry.

Morphologic spectrum of cutaneous B-cell lymphomas

Cutaneous B-cell lymphomas represent a heterogeneous group of entities which show variation in histology, immunophenotype, and in prognosis. In the current review the morphologic spectrum of cutaneous B-cell lymphomas comprising primary and secondary cutaneous B-cell lymphomas is discussed according to the REAL classification scheme.

The revised European-American Classification of Lymphoid Neoplasms (REAL): a preferred approach for the classification of cutaneous lymphomas

The Revised European-American Classification of Lymphoid Neoplasms (REAL) classification is based on the principle that each type of lymphoma is a distinct disease defined by morphology, immunophenotypic and genetic features, clinical presentation, and course. If either primary or secondary involvement of the skin is a constant factor, this aspect is considered integral to disease definition. Organ-specific classification schemes, such as that proposed by the European Organization for Research and Treatment of Cancer (EORTC) for cutaneous lymphomas, are not required, and indeed may impede the recognition of common features of diseases involving multiple anatomic sites. The use of multiple classification systems is a step backward, and may lead to confusion among hematologists/oncologists and dermatologists. Nevertheless, cutaneous lymphomas in many instances are distinct. Their natural history is often more indolent than nodal lymphomas, and for that reason they often require different therapeutic approaches. We agree with the efforts of the EORTC classification to emphasize the unique clinical aspects of many cutaneous lymphomas, as this recognition is essential for appropriate clinical management. As has been learned for nodal lymphomas, clinical features play an important role in prognosis and should be used in guiding therapy. For cutaneous lymphomas, the presence or absence of systemic spread is particularly important.

Cutaneous lymphoid hyperplasia and cutaneous marginal zone lymphoma: comparison of morphologic and immunophenotypic features

Cutaneous marginal zone lymphoma (MZL) is a recently described low-grade B-cell lymphoma that usually follows an indolent course. This tumor shares many histologic and clinical features with cutaneous lymphoid hyperplasia (CLH), a benign reactive lymphoid proliferation. Sixteen biopsy specimens from 14 patients with CLH were studied, and compared with 16 cases of cutaneous MZL (9 primary cutaneous, 7 with secondary involvement of the skin) to determine whether there were features that would permit their distinction on routinely fixed, paraffin-embedded tissue sections. Both disorders showed a female preponderance (CLH: 9 F, 5 M; MZL: 11 F, 5 M). The median age was also similar (CLH: 54 years; cutaneous MZL: 55 years). CLH was most common on the arm (8) and the head and neck (7) but also involved the trunk (1); primary cutaneous MZL most often involved the limbs (3), trunk (3), and head and neck (3). Lymphoma did not develop in any of the 14 CLH patients (follow-up ranging from 9 to 246 months, mean 62 months). Six of 9 patients with primary cutaneous MZL and all 7 patients with secondary cutaneous MZL experienced relapses, most commonly isolated to skin or a subcutaneous site. On hematoxylin-eosin stained sections, a diffuse proliferation of marginal zone cells (p < 0.0001), zones of plasma cells (p = 0.01), the absence of epidermal change (p = 0.01), reactive germinal centers (p = 0.03), and a diffuse pattern of dermal or subcutaneous infiltration (p = 0.03) were more often seen in cutaneous MZL. A dense lymphocytic infiltrate, bottom-heavy or top-heavy growth pattern, eosinophils, and a grenz zone were seen equally often in both disorders. Dutcher bodies were observed only in cutaneous MZL. Immunoperoxidase stains on formalin-fixed paraffin-embedded tissue sections showed monotypic expression of immunoglobulin light chains by plasma cells in 11 of 16 MZL cases. By definition, no case with monotypic plasma cells was diagnosed as CLH. In CLH, T cells usually outnumbered B cells, and a B:T cell ratio > or = 3:1 was not observed in any case. By contrast, 40% of the MZL cases showed a B:T cell ratio > or = 3:1. No coexpression of CD20 and CD43 was seen in any case of either MZL or CLH. In summary, the clinical presentations of CLH and MZL are similar. In contrast to historical criteria for diagnosing cutaneous lymphoid infiltrates, the presence of reactive follicles favors a diagnosis of cutaneous B-cell lymphoma (CBCL). In addition, a bottom-heavy or top-heavy growth pattern is not a distinctive finding. Marginal zone cells and zones or sheets of plasma cells are strong morphologic indicators of marginal zone lymphoma. The diagnosis of CBCL can be supported in 40% of the cases by demonstrating a B:T cell ratio of > or = 3:1, and confirmed in 70% of the cases by demonstrating monotypic light chain expression of plasma cells on paraffin sections.

Evaluation of classic architectural criteria in non-mycosis fungoides cutaneous lymphomas

Ninety-seven cases of non-mycosis fungoides (non-MF) cutaneous lymphoma were evaluated employing published criteria for the categorization of B- and T-cell cutaneous malignancies. Included in the study were 77 primary and secondary cutaneous B-cell lymphomas, in which the diagnosis was supported by immunohistochemical studies identifying lineage. These cases were randomized with 20 cases of non-MF and T-cell lymphoma. Hematoxylin and eosin (H & E)-stained slides from each case were reviewed by at least two dermatopathologists, who were unaware of the previous diagnoses, and a judgment regarding histologic pattern was rendered. The histologic criteria employed emphasized architectural features. For B-cell patterns, these included the presence of dense perivascular, periappendageal and/or nodular collections of lymphocytes, centering in the deep dermis, and separation from the epidermis by a grenz zone. Employed criteria for cutaneous T-cell pattern included location restricted primarily to the upper dermis, interstitial pattern, the presence of epidermotropism, and the lack of a grenz zone. Three B-cell lymphomas were judged to have indeterminate patterns. Four of 74 (5.4%) of the remaining B-cell lymphomas were incorrectly categorized as T-cell lymphomas by architectural criteria. The most striking findings included epidermotropism in rare B-cell lymphomas. Three of the four miscategorized cases were large-cell lymphomas. A preference for B-cell pattern was also confirmed in non-MF T-cell lymphomas. We conclude that most B-cell lymphomas in the skin demonstrate a recognizable B-cell pattern, but rarely a pattern more reminiscent of T-cell lymphoma may be seen. This may occur more often with B-large-cell lymphomas. In addition, this study supports previous work indicating that many non-MF T-cell lymphomas show prominent architectural features typically ascribed to B-cell lymphomas. In summary, our findings support the impression that the vast majority of non-MF lymphomas show a B-cell pattern regardless of their lineage. As such, caution is indicated with regard to pattern interpretation.

Primary cutaneous marginal zone B-cell lymphoma: a recently described entity of low-grade malignant cutaneous B-cell lymphoma

Recently a new classification of primary cutaneous B-cell lymphomas (PCBCLs) has been proposed by the European Organization for Research and Treatment of Cancer (EORTC)--Cutaneous Lymphoma Project Group. The marginal zone B-cell lymphomas (MZLs) were not included as a distinct entity because of insufficient experience and controversial opinions. We have studied 32 patients (M:F ratio 1.5:1; age range 25-93 years; mean age 49.6 years; median age 50 years) to determine the diagnostic criteria of primary cutaneous MZL and the relationship with other low-grade malignant PCBCLs. For comparison, three patients with immunocytoma were included in the study. Clinically, patients presented with solitary or clustered reddish or red-brown papules, nodules, and plaques, sometimes surrounded by an erythematous halo. Histopathologic sections showed nodular or diffuse infiltrates involving the dermis and subcutaneous fat. Cytomorphologically small to medium-sized cells with indented nuclei and abundant pale cytoplasm (marginal zone cells, centrocyte-like cells) predominated. In addition, scattered blasts, lymphoplasmacytoid cells, and plasma cells were observed below the epidermis and at the periphery of the infiltrates. Reactive germinal centers were present in 75% of the cases. The three cases of immunocytoma showed a more monomorphous pattern with predominance of lymphoplasmacytoid cells. The marginal zone cells showed a CD20+, CD79a+, CD5- and Bcl-2+ immunophenotype. They expressed immunoglobulin G in the majority of the cases. Staining with the monocytoid B cell-related antibody KiM1p gave positive results in all specimens with a typical intracytoplasmic granular pattern. A monoclonal distribution of immunoglobulin light chains was observed in marginal zone cells in 75% of the cases. Germinal centers, when present, were either polyclonal or negative for both kappa and lambda light chains. Monoclonal rearrangement of the JH gene was detected via polymerase chain reaction (PCR) in 18 of 26 investigated specimens. Analysis in 12 patients of the bcl-2/immunoglobulin heavy chain gene rearrangement using PCR yielded negative results. Lesions were treated by surgical excision followed in some patients by local radiotherapy. Systemic antibiotic therapy was administered to three patients, with good response in two. The prognosis is excellent. After a mean follow-up of 47.9 months (range 6-252; median 24) all patients are alive without signs of systemic lymphoma. Primary cutaneous MZL represents a distinct clinicopathologic subtype of low-grade malignant PCBCL.

The Revised European-American Classification of Lymphoid Neoplasms (REAL): a new perspective for the classification of cutaneous lymphomas

Differing classification schemes for malignant lymphomas have been used in Europe and the United States. Attempts to translate between the principle classifications have been unsuccessful and historically it has been difficult to arrive at an unified approach. In addition, many new lymphoma entities have been recognized in recent years that are not delineated in any of the existing classification schemes. To provide a unified international basis for clinical and investigative work in this field, in 1994 the International Lymphoma Study Group (ILSG) proposed a new classification termed Revised European-American Classification of Lymphoid Neoplasms (REAL). This review discusses the REAL classification, especially as it pertains to cutaneous lymphomas, and provides insight into the clinicopathologic features of lymphoproliferative disease involving the skin. The premise of the REAL classification is that a classification scheme should be based on the delineation of disease entities, utilizing pathologic, immunophenotypic, genetic, and clinical features. Therefore, if cutaneous involvement is an integral aspect of any lymphoma subtype, this clinical information is included in the definition of that neoplasm. We conclude that the principles of the REAL classification are applicable to cutaneous lymphomas, as well as lymphomas involving other anatomic sites.