Cutaneous lymphoid hyperplasias

Cutaneous Reactive B-cell Lymphoid Proliferations

Cutaneous lymphoid hyperplasia (CLH), also known as cutaneous pseudolymphoma, is a spectrum of benign conditions characterized by reactive B- and T-cell cutaneous lymphocytic infiltrates. B-cell lymphoid proliferations are a heterogenous group of non-neoplastic cutaneous diseases that must be histopathologically distinguished from cutaneous B-cell lymphomas. These proliferations can be observed as reactive phenomena to infections, medications, allergens, neoplasms, and more. Further, there are many inflammatory conditions that present with reactive B-cell infiltrates, including actinic prurigo, Zoon balanitis, Rosai-Dorfman, and cutaneous plasmacytosis. This review summarizes multiple cutaneous B-cell lymphoid proliferations within the major categories of reactive and disease-associated CLH. Further we discuss major discriminating features of atypical CLH and malignancy. Understanding the specific patterns of B-cell CLH is essential for the proper diagnosis and treatment of patients presenting with such lesions.

Lymphocytoma cutis (cutaneous B-cell pseudolymphoma): study of 102 cases with emphasis on the histological characteristics and immunohistochemistry of the miliarial type

BACKGROUND

Lymphocytoma cutis (LC) is a benign reactive lymphoproliferative B-cell process. It has two variants: localized type with solitary lesions and miliarial type with numerous lesions. The objective was to investigate the characteristics of LC with emphasis on the miliarial type.

METHODS

Retrospective study, patients with clinical and histopathological diagnosis of LC were included. Age, sex, evolution time, affected site, and type of treatment were investigated. In miliarial-type LC, the histological and immunohistochemical characteristics were also investigated.

RESULTS

In an 18-year period, there were 102 patients found with LC: 72 (71%) corresponded to females, the median age was 45 years, the median evolution time was 4 months, and the face was the most predominant affected area in 81 (79%) cases. Localized-type LC corresponded to 88 (86%) cases, and miliarial type in 14 (14%). The most common treatment was surgery, which was used in 32 (31%) patients, all of whom had localized type (P < 0.01). The most frequent treatment for miliarial-type LC was corticosteroids in five (36%, P = 0.32), the predominant histopathological pattern was nodular in 10 (71%) specimens, and immunohistochemistry was performed in 11 (79%), where all were positive for CD20 with polyclonality to kappa and lambda light chains.

CONCLUSIONS

The importance of LC lies in that it can be clinically and histopathologically confused with cutaneous lymphoma and that it is a rare entity, with its miliarial variant being rarer still. This study provides information on the clinical-histological characteristics of LC and its immunohistochemistry.

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 Pseudolymphoma

The term, cutaneous pseudolymphoma (PSL), refers to a group of lymphocyte-rich infiltrates, which either clinically and/or histologically simulate cutaneous lymphomas. Clinicopathologic correlation is essential to achieve the final diagnosis in cutaneous PSL and to differentiate it from cutaneous lymphomas. A wide range of causative agents (eg, Borrelia, injections, tattoo, and arthropod bite) has been described. Based on clinical and/or histologic presentation, 4 main groups of cutaneous PSL can be distinguished: (1) nodular PSL, (2) pseudo-mycosis fungoides, (3) other PSLs (representing distinct clinical entities), and (4) intravascular PSL. The article gives an overview of the clinical and histologic characteristics of cutaneous PSLs.

Disorders characterized by predominant or exclusive dermal inflammation

Some cutaneous inflammatory disorders are typified by a predominant or exclusive localization in the dermis. They can be further subdivided by the principal cell types into lymphocytic, neutrophilic, and eosinophilic infiltrates, and mixtures of them are also seen in a proportion of cases. This review considers such conditions. Included among the lymphoid lesions are viral exanthems, pigmented purpuras, gyrate erythemas, polymorphous light eruption, lupus tumidus, and cutaneous lymphoid hyperplasia. Neutrophilic infiltrates are represented by infections, Sweet syndrome, pyoderma gangrenosum, and hidradenitis suppurativa, as well as a group of so-called "autoinflammatory" dermatitides comprising polymorphonuclear leukocytes. Eosinophil-dominated lesions include arthropod bite reactions, cutaneous parasitic infestations, the urticarial phase of bullous pemphigoid, Wells syndrome (eosinophilic cellulitis), hypereosinophilic syndrome, and Churg-Strauss disease. In other conditions, eosinophils are admixed with neutrophils in the corium, with or without small-vessel vasculitis. Exemplary disorders with those patterns include drug eruptions, chronic idiopathic urticaria, urticarial vasculitis, granuloma faciale, and Schnitzler syndrome (chronic urticarial with a monoclonal gammopathy).

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.

Approach to Cutaneous Lymphoid Infiltrates: When to Consider Lymphoma?

Cutaneous lymphoid infiltrates (CLIs) are common in routine dermatopathology. However, differentiating a reactive CLI from a malignant lymphocytic infiltrate is often a significant challenge since many inflammatory dermatoses can clinically and/or histopathologically mimic cutaneous lymphomas, coined pseudolymphomas. We conducted a literature review from 1966 to July 1, 2015, at PubMed.gov using the search terms: Cutaneous lymphoma, cutaneous pseudolymphoma, cutaneous lymphoid hyperplasia, simulants/mimics/imitators of cutaneous lymphomas, and cutaneous lymphoid infiltrates. The diagnostic approach to CLIs and the most common differential imitators of lymphoma is discussed herein based on six predominant morphologic and immunophenotypic, histopathologic patterns: (1) Superficial dermal T-cell infiltrates (2) superficial and deep dermal perivascular and/or nodular natural killer/T-cell infiltrates (3) pan-dermal diffuse T-cell infiltrates (4) panniculitic T-cell infiltrates (5) small cell predominant B-cell infiltrates, and (6) large-cell predominant B-cell infiltrates. Since no single histopathological feature is sufficient to discern between a benign and a malignant CLI, the overall balance of clinical, histopathological, immunophenotypic, and molecular features should be considered carefully to establish a diagnosis. Despite advances in ancillary studies such as immunohistochemistry and molecular clonality, these studies often display specificity and sensitivity limitations. Therefore, proper clinicopathological correlation still remains the gold standard for the precise diagnosis of CLIs.

T-cell-predominant lymphoid hyperplasia in a tattoo

Cutaneous lymphoid hyperplasia (CLH) can be idiopathic or secondary to external stimuli, and is considered rare in tattoos. The infiltrate can be predominantly of B or T-cells, the latter being seldom reported in tattoos. We present a case of a predominantly T CLH, secondary to the black pigment of tattooing in a 35-year-old patient, with a dense infiltrate of small, medium and scarce large T-cells. Analysis of the rearrangement of T-cells receptor revealed a polyclonal proliferation. Since the infiltrate of CLH can simulate a T lymphoma, it is important to show that lesions from tattoos can have a predominance of T-cells.

Feline cutaneous lymphocytosis: case report and summary of the literature

Practical relevance:

Feline cutaneous lymphocytosis is a rare disease characterized by proliferation of T and/or B lymphocytes in the dermis. Although some of the clinical and histopathologic findings of this condition can overlap with cutaneous lymphoma, it is important to distinguish these entities since their treatment and clinical outcomes vary greatly.

Scope:

This report presents a summary of the literature on feline cutaneous lymphocytosis and describes a case of this condition which showed some unique clinical features and was successfully controlled with oral glucocorticoids.

Mimics of cutaneous lymphoma: report of the 2011 Society for Hematopathology/European Association for Haematopathology workshop

The Society for Hematopathology and European Association for Haematopathology workshop, from October 27 to 29, 2011, in Los Angeles, CA, exhibited many exemplary skin biopsy specimens with interesting inflammatory changes mimicking features of cutaneous lymphoma. This article reviews features observed in cutaneous lymphoid hyperplasia, cutaneous drug reactions, lupus-associated panniculitis, pityriasis lichenoides, hypereosinophilic syndrome, histiocytic necrotizing lymphadenitis, traumatic ulcerative granuloma with stromal eosinophils, and pigmented purpuric dermatosis, as well as a brief review of the pertinent literature and discussion of submitted conference cases. For the pathologist, it is important to be aware of diagnostic pitfalls as well as the limitations of ancillary testing (eg, clonality studies). Finally, correlation with total clinical information, good communication with clinical colleagues, close clinical follow-up with rebiopsy, and prudent use of laboratory studies are vital and will likely offer the best path toward a correct diagnosis.

Cutaneous B-cell lymphoproliferative disorders: report of the 2011 Society for Hematopathology/European Association for Haematopathology workshop

The diagnosis and classification of the cutaneous B-cell lymphomas can be quite a challenge, with a definitive diagnosis sometimes being elusive, even when an extensive workup has been performed. Distinction of benign from neoplastic disorders can be difficult, with some hyperplasias mimicking lymphomas and vice versa. There are only a limited number of skin-specific B-cell lymphomas, including primary cutaneous follicle center lymphoma and primary cutaneous diffuse large B-cell lymphoma, leg type. Cutaneous marginal zone lymphomas have distinctive features but are classified with the other mucosa-associated lymphoid tissue lymphomas. It is important, however, to also remember that many other B-cell lymphomas/ plasma cell neoplasms can primarily, or more often secondarily, involve the skin. Some may mimic one of the skin-specific lymphomas but have very different clinical implications. Iatrogenic and senescent immunodeficiency-associated lymphoproliferative disorders that are often Epstein-Barr virus (EBV) positive can also primarily involve the skin, including cases also known as EBV-positive mucocutaneous ulcer.

Primary B-cell MALT lymphoma of the palate: A case report and distinction from benign lymphoid hyperplasia (pseudolymphoma)

Diagnosis of palatal swellings is a challenge. Benign and malignant tumors may be misinterpreted as lesions of inflammatory origin. We present a case of B-cell non-Hodgkin lymphoma on the palate of a 40-year-old male. A number of factors can make the diagnosis of oral lymphoma difficult. Many lymphomas are extranodal, there is usually a prominent superimposed nonspecific inflammatory response and thus they mimic benign lymphoid hyperplasia. It is important for the pathologist to be familiar with features that distinguish benign from malignant lymphoid proliferations.

Treatment of cutaneous lymphoid hyperplasia with the monoclonal anti-CD20 antibody rituximab

B-cell lymphoproliferative disorders are a continuum from benign cutaneous lymphoid hyperplasia (CLH) or "pseudolymphoma" to primary cutaneous B-cell lymphoma (PCBCL). Historically, CLH was treated with a combination of antibiotics, topical or intralesional corticosteroids, and/or localized radiotherapy. Rituximab, a monoclonal antibody that targets the CD20 marker on B cells, is an effective and well-reported treatment for PCBCL. We review the pathogenesis and current treatments of B-cell lymphoproliferative disorders and assess the role of rituximab for potential therapy in the setting of refractory CLH. We describe a case of CLH that was treated with intralesional rituximab. The patient had notable clinical improvement over the treatment period with rituximab. Because of some persistent and recurrent erythematous areas, topical tacrolimus was initiated, with significant clinical improvement. There were no reported side effects. Management of CLH with intralesional rituximab has been described. The treatment presented in this report substantiates rituximab as a reasonable therapeutic option for refractory CLH after failure of several other widely accepted treatments. Treatment with intralesional rituximab should be reserved for patients with documented CD20(+) lesions.

Childhood cutaneous lymphoid hyperplasia following feline scratches

Cutaneous lymphoid hyperplasia or pseudolymphoma is a usually benign inflammatory response that mimics lymphoma. Stimulation from foreign antigens introduced into the skin can induce this response. Scratches from pets are an effective mode of transmitting infections and inoculating foreign antigens into the skin. We report an unusual case of a child where cutaneous lymphoid hyperplasia presented as subcutaneous nodules at sites scratched by a pet cat.

Castleman's disease of the chest wall

Primary Castleman's disease of the chest wall is unusual. Furthermore, such tumors arising from a surgical wound are extremely rare. We report a 33-year-old female with a history of a thoracic surgery at 5 years of age. A round, homogenous 4 x 3.5-cm mass protruded into the thoracic cavity on the posterior portion of the previous posterolateral incision. The tumor was completely removed, with combined rib resection. The resected specimen showed Angiofollicular Lymph Node Hyperplasia (Castleman's disease), hyaline-vascular type. No recurrence has been found for 10 years. This is the first report of primary chest wall Castleman's disease arising from the surgical wound.

Clusterin expression in cutaneous CD30-positive lymphoproliferative disorders and their histologic simulants

BACKGROUND

Clusterin is a ubiquitous 80 kDa heterodimeric glycoprotein previously shown to be expressed on tumor cells of systemic and, to a lesser extent, primary cutaneous anaplastic large cell lymphoma (PC-ALCL). Lymphomatoid papulosis (LyP), an important differential diagnosis of ALCL, has been studied for clusterin expression in only a small number of cases. The aim of this study was to compare clusterin immunostaining patterns in LyP and other cutaneous histologic simulants with those of PC-ALCL.

METHODS

Formalin-fixed, paraffin-embedded sections of PC-ALCL (6), LyP (20), mycosis fungoides with large cell transformation (MF-LCT, 12), pityriasis lichenoides et varioliformis acuta (PLEVA, 12), arthropod bite reaction (ABR, 12) and lymphomatoid reactions (LR, 9) were immunostained for clusterin and evaluated for staining pattern and distribution. All diagnoses were made with clinicopathologic correlation.

RESULTS

Characteristic dot-like Golgi staining was identified in 10/20 LyP (50%), 4/6 PC-ALCL (67%) and 9/12 MF-LCT (75%). Two of 12 PLEVA (17%), 1 of 12 ABR (8%) and 2 of 8 LR (25%) had lymphocytes (< 25%) with diffuse cytoplasmic staining. Dermal dendritic cells stained strongly for clusterin. High background staining occurred in some cases.

CONCLUSION

Clusterin immunostaining does not reliably distinguish between LyP, PC-ALCL or MF-LCT, but could distinguish LyP from its reactive histologic simulants.

Two pediatric cases of primary cutaneous B-cell lymphoma and review of the literature

Primary cutaneous lymphomas are rare in the pediatric population and most often represent mycosis fungoides or CD30+ lymphoproliferative disorders. Primary cutaneous B-cell lymphoma has rarely been reported in children, and in the past may have been mistaken for disseminated nodal disease or benign cutaneous lymphoid hyperplasias. We describe two cases of marginal zone primary cutaneous B-cell lymphoma in young males. Thus far both have been managed with local therapy. We review the literature of this rare malignancy.

The solitary lymphomatous papule, nodule, or tumor

BACKGROUND

Lymphoma and reactive lymphoid infiltrates presenting as solitary lesion pose a diagnostic and prognostic dilemma for the clinician.

OBJECTIVE

We sought to review prognosis and treatment of suggestive solitary lymphoma lesions.

METHODS

A retrospective chart review was conducted in 27 patients who presented with a single solitary lesion suggestive of lymphoma at a cancer center.

RESULTS

Eighteen of 27 patients' (66.7%) lesions were diagnosed as lymphoma by histology and the remainder was classified as reactive lymphoid infiltrates. Only one patient's lymphoma was systemic at presentation and one progressed later. In all, 23 patients (85.2%) subsequently experienced prolonged, complete remissions. The treatments used varied from none or conservative to chemotherapy, with the more aggressive treatments directed especially against lymphomas or recurrent diseases.

LIMITATIONS

This study is limited by the number of patients and follow-up duration (average 36.8 months, range 3-133 months).

CONCLUSION

Patients presenting with a solitary lesion suggestive of lymphoma and negative staging work-up results generally have a good prognosis. Excellent prognosis is usually expected for benign lesions.

Study of the reactive dendritic cells in small B-cell lymphoproliferations of the skin

Distinguishing between low-grade primary cutaneous B-cell lymphoma (LG-pCBCL) and cutaneous lymphoid hyperplasia (CLH) based on histological features is often difficult. CLH lesions contain numerous reactive cells of the histiocyte lineage [Langerhans cells (LC), dermal dendritic cells (DDC), and macrophages], which are also often present in CBCL. The aim of this study was to determine whether immunohistochemical detection of those cells could help differentiate between CLH and LG-pCBCL. We determined the percentages of those histiocytic cells in the dermal infiltrates of 45 cases of cutaneous lymphoproliferations comprising 16 CLH and 29 LG-pCBCL (19 follicle-center cell lymphomas and 10 marginal zone lymphomas) by immunohistochemical labeling with antibodies to CD1a, FXIIIa, and CD68 to respectively detect LC, DDC, and macrophages. To avoid observer-dependent bias, an automated morphometric analysis method was used to recognize immunoreactive cells and calculate their percentages within the infiltrate. FXIIIa(+) cells were significatively more frequent in CLH than in LG-pCBCL, whereas CD1a(+) and CD68(+) cell frequencies were comparable in the two groups. The results of our study suggest that DDC might play an important role in the genesis of cutaneous lymphomas.

Primary Cutaneous Lymphoproliferative Disorders With Dual Lineage Rearrangement

We present a series of 15 cases of cutaneous lymphoma and pseudolymphoma with dual lineage rearrangement identified among approximately 1200 cases of cutaneous lymphoproliferative disorders assessed in our 4 institutions during the last 8 years in which the results of both T-cell receptor and immunoglobulin heavy chain rearrangement investigations were available. On the basis of the clinicopathologic information, the cases were retrospectively subdivided into 2 categories: (1) cases with definite features of cutaneous lymphoma or pseudolymphoma (n = 11) and (2) cases with unclassifiable disease (n = 4). The detection of dual genotype in the first group did not influence the final diagnosis; 7 cases represented cutaneous B-cell lymphomas, 3 pseudolymphomas, and 1 case lymphomatoid papulosis. The presence of monoclonal T-cell receptor-gene rearrangements in these cases may be explained either by monoclonal or oligoclonal expansion of exuberant T cells (or B cells in case of lymphomatoid papulosis) or by lineage infidelity. Three patients with unclassifiable disease had several clinical and histopathologic features in common. They were elderly, presented with solitary lesions, were in good general health and histopathologically demonstrated a dense multinodular infiltrate containing approximately an equal number of T and B cells and a high number of histiocytes forming granulomas, with prominent granulomatous features in 2 cases. B cells were either scattered with the infiltrate or formed collections vaguely resembling follicles; Reed-Sternberg-like cells were seen in 2 cases. B cells showed expression neither of immunoglobulin light chain. The T-cell component was represented mainly by small, well-differentiated lymphocytes or slightly pleomorphic cells, with some medium-sized convoluted cells. Epstein-Barr virus was not detected by polymerase chain reaction. The exact classification of these cases is unknown; they differ histopathologically from previously published cases of bigenotypic cutaneous lymphomas. They may merely represent a growth or reactive pattern, but, on the other hand, may be low-grade lymphomas. If so, they may be histopathologically related to cutaneous Hodgkin disease, T-cell/histiocyte-rich large B-cell lymphoma, or composite lymphomas. Further reports are needed to identify these lesions to clarify their nature and biologic potential.

Massive cutaneous follicular lymphoid hyperplasia in a patient with the Sjögren syndrome: 7-year follow-up and immunohistochemical study

The Sjögren syndrome often gives rise to complications such as pseudolymphomas and/or mucosa-/skin-associated lymphocytic tumors (MALT/SALT lymphomas). This paper presents a 74-year-old female patient with the Sjögren syndrome complicated by cutaneous plaques/tumors as cutaneous lymphoid hyperplasia over a 7-year follow-up study period. Immunohistochemical examination disclosed B-cell rich lymphoid follicle formation in the skin with the presence of T and B cells and a varied assortment of features to include abundant plasma cell infiltration. Based on the clinical course and histopathological findings, patient condition was considered benign and arises from reaction toward certain unknown microbes.

New aspects in the biology of cutaneous B-cell lymphomas

Immunologic and molecular genetic studies greatly contributed to a better understanding and interpretation of the distinct clinico-pathologic features of primary cutaneous B-cell lymphomas (CBCL), which are the basis for the consensus WHO-EORTC classification. There is increasingly accumulating evidence that these well defined clinico-pathologic entities of CBCL have specific immunologic and molecular features, which further support their nosologic categorization as well as either interesting similarities with other extranodal B-cell lymphomas or definite peculiarities as compared to nodal B-cell lymphomas of similar histotype (specifically, follicle center lymphoma and diffuse large B-cell lymphoma).

Cutaneous lymphoid hyperplasia and other lymphoid infiltrates of the breast nipple: a retrospective clinicopathologic study of fifty-six patients

This study characterizes the clinicopathological spectrum of lymphoproliferations involving the breast nipple and/or areola. Morphologic, immunohistochemical, molecular-genetic, and clinical features of 58 specimens from 56 patients were analyzed. They were re-diagnosed as cutaneous lymphoid hyperplasia (CLH, n = 44); other benign lymphoid infiltrates (OBLI, n = 8); peripheral T-cell lymphoma, not otherwise specified (n = 1); cases with overlapping features of CLH and B-cell lymphoma (n = 3), one of them composed of spindle cells. Cutaneous lymphoid hyperplasia infiltrates were dense, composed mainly of B cells forming follicles with germinal centers (GC). Cutaneous lymphoid hyperplasia frequently showed features suggesting a malignancy as coalescing follicles with non-polarized germinal centers lacking mantle zones, and smudged infiltrates of lymphoid cells spreading into collagen (often as "Indian files"), smooth muscle, vessel walls, and nerve sheaths. Only two cutaneous lymphoid hyperplasias recurred; otherwise all patients are without disease (mean follow-up 62 months). Monoclonal rearrangement of immunoglobulin heavy chain gene was detected in five, and of T-cell receptor gamma gene in two cutaneous lymphoid hyperplasias using polymerase chain reaction (PCR), but the patients fared well too. In 47% of cases Borrelia burgdorferi was detected by polymerase chain reaction and/or serology, of which one was monoclonal. We conclude that cutaneous lymphoid hyperplasia is the most common lymphoproliferation of the breast nipple, rarely recognized clinically, and often overdiagnosed histologically as lymphoma.

Successful antibiotic treatment of Borreliosis associated pseudolymphomatous systemic infiltrates

The clinical management of late stage Borreliosis can be difficult due to various associated symptoms and signs and cumbersome microbiological tests. We report a case of successful antibiotic treatment of Borreliosis-associated pseudolymphomatous infiltrates in bone marrow and lymph nodes, which were diagnosed by bone marrow trephine biopsy and positron emission tomography.

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.

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.

Clinical, morphological and immunohistochemical characterization of cutaneous lymphocytosis in 23 cats

Clinical, morphological and immunohistochemical features of cutaneous lymphocytosis, an uncommon disease histologically resembling well-differentiated malignant lymphoma, were characterized in 23 cats. Clinical outcome was correlated with histomorphology and immunophenotype in an attempt to predict benign vs. malignant behaviour. The disease mainly affected older cats. Lesions were solitary in 61% of cats and often characterized by alopecia (73.9%), as well as erythema, scaling and ulceration. The lateral thorax was most commonly affected (43.5%). Pruritus was frequent (65.2%). Systemic signs included anorexia and weight loss. Morphologically, lesions were characterized by dermal infiltrations of well-differentiated CD3+ T-cells (100%) and aggregates of CD79+ B-cells (64.3%). Cutaneous lymphocytosis is slowly progressive and relatively benign, although in some cats systemic signs led to euthanasia. Four of 12 euthanized cats and one live cat also had lymphoid infiltrates in internal organs. Unfortunately, we were unable to predict clinical outcome by histological and immunohistochemical evaluations of skin lesions.

Primary cutaneous B-cell lymphomas: a practical approach

PCBCL are a heterogeneous group of B-cell lymphomas that originate in the skin, with the absence of extracutaneous disease at diagnosis. Overall, these cutaneous lymphomas have an excellent prognosis. Recurrences are common but dissemination is rare. The EORTC classification allows a more uniform diagnosis and treatment of patients with PCBCL. Careful clinical and pathologic correlation is critical in confirming a diagnosis of PCBCL, before deciding on therapy. Several therapeutic options that are aimed at cure, are available. In most instances, chemotherapy should not be the first line of treatment.

Classification and prediction of survival in patients with the leukemic phase of cutaneous T cell lymphoma

We have used cDNA arrays to investigate gene expression patterns in peripheral blood mononuclear cells from patients with leukemic forms of cutaneous T cell lymphoma, primarily Sezary syndrome (SS). When expression data for patients with high blood tumor burden (Sezary cells >60% of the lymphocytes) and healthy controls are compared by Student's t test, at P < 0.01, we find 385 genes to be differentially expressed. Highly overexpressed genes include Th2 cells-specific transcription factors Gata-3 and Jun B, as well as integrin beta1, proteoglycan 2, the RhoB oncogene, and dual specificity phosphatase 1. Highly underexpressed genes include CD26, Stat-4, and the IL-1 receptors. Message for plastin-T, not normally expressed in lymphoid tissue, is detected only in patient samples and may provide a new marker for diagnosis. Using penalized discriminant analysis, we have identified a panel of eight genes that can distinguish SS in patients with as few as 5% circulating tumor cells. This suggests that, even in early disease, Sezary cells produce chemokines and cytokines that induce an expression profile in the peripheral blood distinctive to SS. Finally, we show that using 10 genes, we can identify a class of patients who will succumb within six months of sampling regardless of their tumor burden.

Heavy multinodular cutaneous lymphoid infiltrates: clinicopathologic features and B-cell clonality

BACKGROUND

Criteria for distinguishing between cutaneous lymphoid hyperplasia (CLH) and low-grade B-cell lymphoma are not well defined. We examined the hypothesis that the presence of a clonal B-cell population in heavy multinodular lymphoid infiltrates correlates with clinical presentation and outcome.

METHODS

We identified 29 patients with skin lesions characterized histologically by a heavy dermal lymphocytic infiltrate with a multinodular architecture and extension into deep dermis and subcutaneous fat. Clonality was assessed immunophenotypically by light-chain restriction and also by analysis for IgH-gene rearrangement using PCR on DNA extracted from paraffin blocks.

RESULTS

Follow-up (mean 80 months; median 45 months) was obtained in all patients. Twenty-four patients (83%) presented with a solitary lesion: only four had solitary recurrences, and none developed multiple synchronous lesions or systemic B-cell lymphoma. However, 9/24 of these solitary lesions (38%) were clonal by light-chain restriction or IgH PCR; 5/29 patients (17%) presented with multiple recurrent lesions and continued to develop lesions during the period of follow-up; 3/5 patients (60%) with multiple lesions demonstrated a B-cell clone. No patient developed systemic B-cell lymphoma.

CONCLUSIONS

Heavy, multinodular cutaneous lymphoid infiltrates have an excellent prognosis. Multiple lesions at presentation are the best predictor of recurrent multiple lesions confined to the skin. The presence of a clonal B-cell population does not correlate with clinical presentation or histology, nor does it predict development of further lesions or systemic lymphoma.

Reduced number of CD1a+ cells in cutaneous B-cell lymphoma

Cutaneous B-cell lymphoma is difficult to distinguish from pseudolymphoma. The histologic pattern and monoclonal restriction (immunohistochemical analysis and molecular biology) are the criteria used for differentiating these entities. CD1a+ dendritic cells have been observed in the infiltrates of T-cell lymphoma, but the presence of these CD1a+ cells has not been compared in B-cell lymphoma and pseudolymphoma. We studied the presence of CD1a+ cells on frozen sections of 23 B-cell lymphomas, 13 pseudolymphomas, and 17 T-cell lymphomas by immunohistochemical analysis. We found abundant CD1a+ dendritic cells in only 1 (4%) of 23 B-cell lymphomas, whereas in 8 (62%) of 13 pseudolymphomas and 17 (100%) of 17 T-cell lymphomas, strong CD1a staining was present. Our study demonstrates a distinct pattern of CD1a staining in the infiltrates of B-cell lymphoma and pseudolymphoma that may be of value in the differential diagnosis of these skin disorders.