Immunophenotypic and genotypic analysis in cutaneous lymphoid hyperplasias

Pseudolymphoma to Lymphoma: A Case of Chronic Reactive Lymphoid Hyperplasia Transforming to Primary Cutaneous Marginal Zone Lymphoma

ABSTRACT

Primary cutaneous marginal zone lymphoma (PCMZL) is a low-grade malignant B-cell lymphoma that originates from the skin. It often presents as erythematous solitary or multiple papules, nodules, and/or plaques. It is one of the 3 main subtypes of primary cutaneous B-cell lymphomas. PCMZLs are believed to develop from chronic antigenic stimulation such as from tick-borne bacteria, vaccines, tattoo pigment, or other foreign body. In addition, cutaneous lymphoid hyperplasia, a documented precursor to malignant PCMZL, often presents in response to areas of chronic inflammation. Cutaneous lymphoid hyperplasia and PCMZL share several clinical and histological similarities that require clinicopathologic suspicion, immunohistochemical ancillary studies, and histopathologic analysis to accurately differentiate the 2 entities. Although gene rearrangement studies have historically been of limited value in the diagnosis of PCMZL, recent studies investigating molecular markers have identified the presence of multiple genetic abnormalities that have helped to better characterize the disease and aid in diagnosis. In addition, newer studies have found associations between PCMZL and gastrointestinal disorders, including Helicobacter pylori and inflammatory bowel disorders. In this article, we describe a case of a 56-year-old patient with a history of ulcerative colitis presenting with chronic reactive lymphoid hyperplasia that transformed to primary cutaneous marginal zone lymphoma.

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.

Cutaneous Lymphoid Hyperplasia With T-Cell Clonality and Monotypic Plasma Cells Secondary to a Tick Bite: A Hidden Critter and the Power of Deeper Levels

Cutaneous lymphoid hyperplasia (CLH) is a benign reactive process with T-cell or B-cell lymphocytic infiltration in the skin, which can simulate cutaneous lymphomas both clinically and histologically. Various antigenic stimuli have been implicated in the development of CLH, including tick bites. Finding histologic evidence of such triggering factors, however, is often difficult. Moreover, the presence of clonality in CLH can potentially be interpreted as a neoplastic process, posing a further diagnostic challenge to dermatopathologists, if one is not aware of such peculiar phenomena. Herein, we describe a case of CLH secondary to a tick bite, featuring both T-cell clonality and monotypic plasma cells with lambda light chain restriction; the diagnostic clue being tick parts, which became evident on assessment of deeper levels. To the best of our knowledge, this is the first reported case of a tick-associated clonal CLH with simultaneous detection of monoclonal T cells and monotypic lambda light chain restriction, mimicking primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder and Borrelia-associated primary cutaneous marginal zone B-cell lymphoma, respectively.

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.

Progression of Cutaneous B-Cell Pseudolymphoma to Cutaneous B-Cell Lymphoma

Background:

Debates regarding nosology and clonality surround the entity known as cutaneous pseudolymphoma and its questionable transformation to frank cutaneous lymphoma. The relevance of these arguments is important, not only from a diagnostic standpoint, but also for making inferences based upon behavior, prognosis, and treatment.

Objective:

Our goal was to demonstrate further evidence of progression from cutaneous pseudolymphoma to malignant lymphoma while at the same time advocating a comprehensive plan for evaluation, treatment, and followup of these patients.

Methods:

A retrospective review was conducted of four patients initially considered to have cutaneous B-cell pseudolymphoma (CBPL) and who were later treated for primary cutaneous B-cell lymphoma (CBCL). A review of the literature of cases suggesting progression to malignant lymphoma from precursor lesions was also performed.

Results:

Four patients initially diagnosed with CBPL by a combination of histologic, immunophenotypic, and gene rearrangement criteria had a progressive clinical course that, over a range of 17–51 months, evolved into CBCL. All patients had a comprehensive systemic workup to rule out the possibility of extracutaneous disease and were treated with local radiation therapy and close followup. There has been no evidence of extracutaneous disease with an average followup of 14 months.

Conclusion:

The potential for certain cutaneous pseudolymphomas to progress to CBCL is real. The combination of histologic and immunophenotypic criteria, along with the clinical picture, remains the best way to judge the aggressiveness of the lesion. Gene rearrangement studies, whether performed by Southern blot or polymerase chain reaction (PCR), are of limited value and should be used to support the overall clinicopathologic picture. Radiation therapy of these patients should be thought of early in the management plan and is a very successful form of treatment when combined with close followup.

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.

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.

Pseudoneoplastic lesions: general considerations

Pseudoneoplastic lesions ("pseudotumors") can be seen in virtually all anatomic locations. Some organ sites, such as the lungs and skin, are overrepresented for unknown reasons, and the histologic images seen in pseudoneoplastic lesions are partially overlapping in disparate locations. More than occasionally, the degree of histologic likeness to true neoplasms-often malignant ones-is striking. This overview outlines the spectrum of pseudoneoplastic lesions and divides them into etiologic categories, including reparative, developmental, functional (usually endocrine), iatrogenic, infectious, and idiopathic. Side-by-side pictorial comparisons of selected pseudoneoplastic lesions and their neoplastic mimics are included.

Transformation of vulvar pseudolymphoma (lymphoma-like lesion) into a marginal zone B-cell lymphoma of labium majus

Lymphomas arising in the female genital tract are extremely uncommon. Diffuse large B-cell lymphoma and follicular lymphoma are the most common types. We describe the case of an 80-year-old woman with a recurrent lesion in the vulva initially diagnosed as a lymphoma-like lesion and evolving 7 years later into a marginal zone B-cell lymphoma (lymphoplasmacytic lymphoma). Diagnosis was based on the monotypic pattern of the plasmacellular component and the clonal rearrangement of immunoglobulin heavy chain genes. No previous cases of vulvar marginal zone B-cell lymphoma arising in the context of a persistent lymphoma-like lesion have been reported. We highlight the importance of differentiating benign from malignant lymphoid infiltrates in the vulva.

Recent advances in cutaneous lymphomas

Cutaneous lymphomas are a heterogeneous group of extranodal lymphomas that are characterized by an initial accumulation of mononuclear, mostly lymphocytic cells in the skin. Recent discoveries of changes in molecular biology and immunology of these tumors have paved the way to a better understanding of the processes that govern lymphomagenesis in the skin and more importantly, they have contributed to the development of the new WHO-EORTC classification system. Only now has the field of cutaneous lymphomas gained a novel, long-awaited basis that may act as a new starting point in the collection of clinical as well molecular and immunological data on comparative basis. This review will try to highlight the newest findings in the pathogenesis of primary cutaneous T- and B-cell lymphomas, hematodermic neoplasm and HTLV-1 positive disorders as well as their translation into efficient therapeutic strategies.

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.

Primary cutaneous B-cell lymphoma

Primary cutaneous B-cell lymphomas include extranodal marginal zone B-cell lymphoma, follicular lymphoma, large B-cell lymphoma, and, rarely, mantle cell lymphoma. Our purpose in conducting this review was to determine the clinical and behavioral characteristics of primary cutaneous B-cell lymphomas, their relationship to infectious triggers, and therapeutic response. We conducted a retrospective chart review of 23 adult patients presenting to the dermatology clinic at M. D. Anderson Cancer Center with primary cutaneous B-cell lymphoma between January 1999 and May 2003. Primary cutaneous B-cell lymphomas generally present on the head and neck, with the trunk and extremities afflicted to a lesser extent. Patients were found to have serologic evidence of prior infection with Borrelia burgdorferi (n = 10), Helicobacter pylori (n = 5), and Epstein-Barr virus (n = 6). Overall, treatment of primary cutaneous B-cell lymphoma should involve multiple modalities; however, specific treatment aimed at concurrent or suspected infection, particularly B burgdorferi, is a helpful adjunct and may achieve complete remission in a small subset of patients.

Borrelia burgdorferi-associated lymphocytoma cutis: clinicopathologic, immunophenotypic, and molecular study of 106 cases

Lymphocytoma cutis (LC) is considered as the stereotypical example of the cutaneous B-cell pseudolymphomas. It can be induced by various antigenic stimuli including arthropod bites, vaccination, and drugs among others. In endemic regions, Borrelia burgdorferi is the principal causative agent for LC. We studied retrospectively 108 biopsies from 106 patients (male : female, 48 : 58; mean age, 44.6; median, 51.5; range, 3-81) with B. burgdorferi-associated LC retrieved from the files of the Department of Dermatology of the University of Graz (Austria). Only cases with a B. burgdorferi etiology (typical locations, positivity of serologic and/or polymerase chain reaction (PCR) tests, clinical history) were included in the study. Lesions were located on the nipple (63 cases), earlobe (18 cases), genital region (9 cases), and trunk or extremities (16 cases). PCR analysis of B. burgdorferi DNA was positive in 54 of 80 cases tested (67.5%). In 47 cases, we could retrieve data on serologic examination for B. burgdorferi antibodies performed at the time of diagnosis of LC. Positivity was found in 45 patients (IgG+/IgM+, 5 cases; IgG+/IgM-, 37 cases; IgG-/IgM+, 3 cases; IgG-/IgM-, 2 cases). Histology revealed dense lymphoid infiltrates with prominent germinal centers (GCs) in all cases. Atypical morphologic and/or immunophenotypic features of the GCs were commonly observed. In 5 cases, due to confluence of large follicles, the histopathologic pattern simulated that of a large B-cell lymphoma. PCR analysis of the IgH gene rearrangement performed in 33 cases showed a polyclonal pattern in 31 cases and a monoclonal band in 2. In summary, B. burgdorferi-associated LC can present with misleading histopathologic, immunophenotypic, and molecular features, and integration of all data is necessary for a correct diagnosis.

Cutaneous lymphoid hyperplasia: a lymphoproliferative continuum with lymphomatous potential

Cutaneous lymphoid hyperplasia (CLH) has been proposed to be the benign end of a continuum of lymphoproliferative disorders with cutaneous lymphoma at its malignant extreme. An intermediate condition, known as "clonal CLH," was first recognized by us and shown to be a transitional state capable of eventuating in overt lymphoma. To better determine the prevalence of dominant clonality and risk of lymphoma among CLH cases, we studied the immunohistology and clonality of fresh-frozen samples from 44 CLH patients referred to a multidisciplinary cutaneous lymphoproliferative disorders program. Using a large panel of lymphoid markers, the cases were divided into 38 typical mixed B-cell/T-cell type CLH and 6 T-cell-rich type (T-CLH), the latter containing > 90% T cells. Of the 44 patients, 38 had solitary or localized lesions (4 cases of T-CLH), and 6 had regional/generalized lesions (2 cases of T-CLH). Forty cases were of idiopathic etiology. Suspected etiologies among 4 other cases included mercuric tattoo pigment, doxepin, clozapine, and bacterial infection. Immunoglobulin heavy chain (IgH) and T-cell receptor (TCR)-gamma gene rearrangements (GR) were studied using polymerase chain reaction assays, which are approximately 80% sensitive. Overall, 27 cases (61%) showed clonal CLH: 12 IgH+ (27%; 3 cases of T-CLH); 13 TCR+ (30%; 1 case of T-CLH); and 2 IgH+/TCR+ (4%; neither case was T-CLH). Two cases (4%; 1 case of T-CLH) progressed to cutaneous B-cell lymphoma. Both of these patients presented with regional lesions. Our findings indicate that clonal overgrowth is common in CLH, links CLH to lymphoma, and probably involves both B- and T-cell lineages (although TCR GR by B cells and vice versa could not be ruled out). The high prevalence of dominant clonality in our series may have resulted from the sensitivity of our PCR assays as well as patient selection.

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.

Primary cutaneous follicle center cell lymphomas and large B cell lymphomas of the leg descend from germinal center cells. A single cell polymerase chain reaction analysis

Primary cutaneous B cell lymphomas are defined as non-Hodgkin lymphomas that occur in the skin without extracutaneous involvement for 6 mo after diagnosis. They are characterized by a less aggressive course and better prognosis than their nodal counterparts. According to the European Organization for Research and Treatment of Cancer classification, the major subentities of primary cutaneous B cell lymphoma are follicle center cell lymphomas, immunocytomas, and large B cell lymphomas of the leg, which differ considerably regarding their clinical behavior, the former two being indolent, the latter being of intermediate malignancy. In this study, we applied a single cell polymerase chain reaction approach to analyze immunoglobulin V(H)/V(L) genes in 532 individual B lymphocytes from histologic sections of four follicle center cell lymphomas localized on the head and trunk, and four large B cell lymphomas on the leg. We found: (i) in six of eight patients a clonal heavy chain, and in seven of eight patients a clonal light chain rearrangement, all being potentially productive; (ii) no bias in VH gene usage, in four of seven light chain rearrangements the V kappa germline gene IGVK3-20*1 was used; (iii) no biallelic rearrangements; (iv) all V(H)/V(L) genes are extensively mutated (mutation rate 5.4-16.3%); (v) intraclonal diversity in six of eight cases (three of each group); and (vi) low replacement vs silent mutation ratios in framework regions indicating preservation of antigen-receptor structure, as in normal B cells selected for antibody expression. Our data indicate a germinal center cell origin of primary cutaneous follicle center cell lymphomas and large B cell lymphomas independent of those belonging to one of these subentities.

Persistent pigmented purpuric eruption associated with mycosis fungoides: a case report and review of the literature

A purpuric eruption may be an unusual early manifestation of mycosis fungoides (MF). On the other hand, persistent pigmented purpuric dermatoses (PPPD) may, occasionally, evolve to cutaneous T-cell lymphoma. Coexistence of these two conditions has been reported, but it is extremely rare. We present the case of an elderly woman with a long-standing pruritic, pigmented purpuric eruption. On 1-year follow-up, histological features suggesting early MF were observed and molecular analysis of the rearrangement of T-cell receptor genes revealed clonality. Our patient may represent a case of PPPD evolving to MF, a case of MF clinically featuring PPPD, or an intermediate condition in a nosological continuity extending from PPPD to MF. A persistent pigmented purpuric eruption may rarely be a harbinger of cutaneous T-cell lymphoma. Therefore, vigilant long-term follow-up of PPPD is highly recommended.

Cutaneous lymphoid hyperplasias

Benign hyperplastic lymphoid infiltrates of the skin (pseudolymphoma, older term) simulate lymphoma clinically and histologically. They can be divided into B-cell predominant (typical cutaneous lymphoid hyperplasia (CLH), angiolymphoid hyperplasia, Kimura's disease, and Castleman's disease) and T-cell predominant (T-cell CLH, lymphomatoid contact dermatitis, and lymphomatoid drug eruption). Both types may represent exaggerated reactions to diverse external antigens (insect bite, tattoo, zoster, trauma, among others). A composite assessment of clinical presentation and behavior, routine histology, immunophenotyping, and molecular studies is essential for the diagnosis of benign cutaneous lymphoid infiltrates. Treatment includes antibiotics, intralesional and systemic corticosteroids, excision, radiotherapy, and immunosuppressants. Treatment depends on the assessment and biologic behavior, which is usually benign. Molecular biologic analysis has shown that a significant proportion of cases harbor occult B- or T-cell clones (clonal CLH). Progression to overt cutaneous lymphoma has been observed in a minority of cases. Patients with clonal populations of B or T cells and persistent lesions should be closely observed for emergence of a lymphoma.

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.

Cutaneous pseudolymphomas

Cutaneous pseudolymphoma refers to a heterogeneous group of benign reactive T- or B-cell lymphoproliferative processes of diverse causes that simulate cutaneous lymphomas clinically and/or histologically. The inflammatory infiltrate is bandlike, nodular, or diffuse and is composed predominantly of lymphocytes with or without other inflammatory cells. Depending on the predominant cell type in the infiltrate, cutaneous pseudolymphomas are divided into T- and B-cell pseudolymphomas. Cutaneous T-cell pseudolymphomas include idiopathic cutaneous T-cell pseudolymphoma, lymphomatoid drug reactions, lymphomatoid contact dermatitis, persistent nodular arthropod-bite reactions, nodular scabies, actinic reticuloid, and lymphomatoid papulosis. Cutaneous B-cell pseudolymphomas include idiopathic lymphocytoma cutis, borrelial lymphocytoma cutis, tattoo-induced lymphocytoma cutis, post-zoster scar lymphocytoma cutis, and some persistent nodular arthropod-bite reactions. This review attempts to discuss current aspects of the classification, pathogenesis, clinical spectrum, histopathologic and immunohistochemical diagnosis, and laboratory investigations for clonality in the various types of cutaneous pseudolymphomas.

Persistent pigmented purpuric dermatitis and mycosis fungoides: simulant, precursor, or both? A study by light microscopy and molecular methods

Mycosis fungoides (MF) can present with purpuric lesions, and rare patients who seemed to have persistent pigmented purpuric dermatitis (PPPD) have developed MF. We recently encountered two patients referred to our cutaneous lymphoma clinic who had PPPD rather than MF and two others who appeared to have both conditions, leading us to explore the histologic similarities of these diseases. We examined specimens from 56 patients with PPPD to determine the frequency of MF-like histologic configurations, namely, the psoriasiform lichenoid, psoriasiform spongiotic lichenoid, and atrophic lichenoid patterns. We also noted the degree of spongiosis, epidermotropism, papillary dermal fibrosis, lymphocytic atypia, and epidermal hyperplasia, the number of extravasated erythrocytes and siderophages, and the distribution of lymphocytic infiltrate within the epidermis. In 29 of 56 patients, there were patterns typically seen in MF. PPPD can feature lymphocytes aligned along the epidermal side of the dermoepidermal junction, with few necrotic keratinocytes, as can MF. Papillary dermal edema occurred frequently in PPPD but not in MF, while lymphocytes in MF but not PPPD had markedly atypical nuclei and had ascended into the upper spinous layer. Given these similarities, we tested for clonality of the T-cell population using a polymerase chain reaction assay for gamma-chain rearrangements. Clonal populations were present in three of three and one of two specimens from patients with both PPPD and MF, but also in 8 of 12 specimens typical of lichenoid patterns of PPPD. These findings raise the possibility that the lichenoid variants of PPPD are biologically related to MF.

Immunohistochemical analysis of dermal mononuclear cell infiltrates in cutaneous lupus erythematosus, polymorphous light eruption, lymphocytic infiltration of Jessner, and cutaneous lymphoid hyperplasia: a comparative differential study

Cutaneous lupus erythematosus (LE), polymorphous light-eruption (PMLE), lymphocytic infiltration of Jessner (LIJ), and cutaneous lymphoid hyperplasia (CLH) are often difficult to differentiate from one another by light microscopic examination. We conducted an immunohistochemical analysis of the mononuclear cell infiltrates in 13 LE, 12 PMLE, 10 LIJ, and 13 CLH with various antibodies. Antibodies L26, UCHL1, and S100 achieved statistically significant differences among the four diseases, but because of the overlaps in the number of UCHL1(+) T cells and S100 protein (+) cells in individual cases, these two antibodies were not useful. Only CLH could be distinguished from LE, PMLE, and LIJ by a greater number of CD20(+) B cells. The latter three conditions could not be differentiated. Contrary to previous reports, plasmacytoid-monocytes were not found to be increased in LIJ for the differentiation of the latter from LE and PMLE. Our results support the conclusion that CLH is a reactive lymphoid hyperplastic process with proliferation of both B and T cells, whereas the T cell was the predominant cell type in the infiltrates of LE, PMLE, and LIJ, indicating that they were related to T cell disorders. The histiocyte was only a minor component cell. The plasmacytoid monocyte in general was not significantly present in all four conditions, but relatively more plasmacytoid monocytes were present in CLH.

Primary cutaneous B-cell lymphomas

Primary cutaneous B-cell lymphomas are malignant B-cell lymphomas that clinically originate in the skin. These lymphomas have a different clinical behavior and prognosis than primary node-based lymphomas of the same histologic subtype. Within the group of primary cutaneous B-cell lymphomas some well-defined clinicopathologic entities can be recognized including primary cutaneous follicle center cell lymphomas, primary cutaneous immunocytomas and cutaneous intravascular B-cell lymphomas. In this review the clinical and histologic features of these lymphomas will be discussed and guidelines for the treatment will be presented.

Detection of clonal T-cell receptor gamma gene rearrangements in early mycosis fungoides/Sezary syndrome by polymerase chain reaction and denaturing gradient gel electrophoresis (PCR/DGGE)

We used a gene amplification strategy to analyze T-cell receptor (TCR) gene rearrangements in 185 specimens, including mycosis fungoides/Sezary syndrome (MF/SS), other cutaneous neoplasms, inflammatory dermatoses, reactive lymphoid tissues, and normal skin. Genomic DNA was extracted from lesional tissues and rearrangements of the TCR-gamma chain gene were amplified using the polymerase chain reaction (PCR) with primers specific for rearrangements involving V gamma 1-8 or V gamma 9 gene segments. The resulting PCR products were then separated according to their nucleotide sequence as well as size by denaturing gradient gel electrophoresis (DGGE). Dominant clonal TCR-gamma gene rearrangements were detected in 61 of 68 MF/SS cases by PCR/DGGE. This sensitivity of 90% compared to a sensitivity of only 59% when dominant clonality was sought in 17 of these same cases by Southern blot analysis of TCR-beta gene rearrangements. This difference in sensitivity was greatest in early, minimally infiltrated skin lesions. PCR/DGGE was also more sensitive than Southern blot analysis for detecting peripheral blood involvement in two cases of early MF. Among 12 additional specimens of suspected MF/SS, nine (75%) showed clonal TCR-gamma gene rearrangements by PCR/DGGE including six of eight cases with a previously confirmed diagnosis of MF/SS and three of four cases without prior known MF/SS. Among 105 non-MF/SS specimens, dominant TCR-gamma gene rearrangements were detected in only six cases (6%). Four were diagnosed as chronic dermatitis and two were diagnosed as cutaneous lymphoid hyperplasia. We conclude that the large majority of MF/SS cases, including patch phase disease, possess dominant clonal TCR-gamma gene rearrangements. PCR/DGGE is more sensitive than Southern blot analysis for detecting dominant clonality and staging disease in patients with a confirmed diagnosis of MF/SS. However, because PCR/DGGE is sensitive enough to detect dominant TCR-gamma gene rearrangements in a subset of patients with chronic dermatitis, it cannot be used as the sole criterion for establishing a diagnosis of T-cell lymphoma. As with other molecular biologic clonality assays, clinicopathologic correlation is essential. Nevertheless, the detection of dominant clonality in some cases of histologically nonspecific dermatitis allows the identification of a previously unrecognized subset of patients, i.e., those with "clonal dermatitis." It will be important to determine the long-term risk of MF/SS among these patients because our study indicated that MF/SS can sometimes present with lesions indistinguishable from clonal dermatitis.