The role of MT2 and anti-bcl-2 protein antibodies in the differentiation of benign from malignant cutaneous infiltrates of B-lymphocytes with germinal center formation

Immunocytochemistry and the diagnosis of cutaneous lymphoma

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

Clinicopathologic reassessment of non-mycosis fungoides primary cutaneous lymphomas during 17 years

BACKGROUND

New classification systems have recently been proposed for primary cutaneous lymphomas (PCLs). The aim of our study was to evaluate the applicability and significance of the new classification systems to the diagnosis and management of non-mycosis fungoides (non-MF) PCL.

METHODS

Immunohistochemical restaining, histological reclassification, and clinical follow-up of all new non-MF PCL cases during 17 consecutive years were performed. The histological reclassification was performed according to the Revised European-American Lymphoma (REAL) classification, except for lymphomatoid papulosis (Lyp), which was included as an indolent lymphoma, according to the European Organization for the Research and Treatment of Cancer (EORTC) classification.

RESULTS

During the period 1983-99, 251 new PCL cases were seen, 213 (85%) of which were MF and Sézary syndrome (eight cases), and 38 (15%) of which were non-MF. Of the latter, 20 (53%) were B-cell lymphomas, including eight (40%) follicle center lymphoma, follicular (FCLF), eight (40%) marginal zone lymphoma (MZL), two (10%) diffuse large cell lymphoma, and two (10%) unclassifiable cases. Most or all of the lesions did not stain for CD10, CD43, and bcl-2 protein, and immunostaining for kappa and lambda immunoglobulin light chain restriction was much more useful diagnostically in MZL. Of the 18 primary non-MF cutaneous T-cell lymphomas, 13 (72%) were Lyp, all of which were type A, four (22%) were CD30+ anaplastic large cell lymphoma, and one (6%) was natural killer (NK)/T-cell lymphoma. Except for the NK/T-cell lymphoma, all the other non-MF PCLs had an indolent course.

CONCLUSIONS

A minority of the routinely diagnosed PCLs are non-MF, equally divided between B- and T-cell lymphomas. The REAL classification is applicable to the majority, although it does not include entities such as Lyp; the clinical correlations are not as obvious because most of the non-MF PCLs tend to have a relatively indolent course.

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

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

Cutaneous follicle center lymphoma: a clinicopathologic study of 19 cases

Cutaneous follicle center lymphoma (FCL) is reported to have a unique immunophenotype and clinical course as compared with nodal FCL. We studied 19 cases of FCL of the skin using paraffin embedded tissue. An immunohistochemistry panel included CD45, CD3, CD20, CD43, CD21, bcl-2, bcl-6, CD5, and CD10. Molecular studies were performed by polymerase chain reaction for immunoglobulin heavy chain (IgH) and t(14;18). Trisomy 3 was performed by fluorescent in situ hybridization (FISH) in 13 cases. Follow up was obtained in 17 cases (range 3 to 137 months). Patients included 10 females and 9 males ranging in age from 33 to 88 years at first presentation (mean, 64). Twelve of 19 presented in the head and neck and 6 in the trunk and 1 on the arm. All had no known lymph node disease at presentation. Seventeen patients had no nodal disease with a minimum 3 month follow-up; 2/19 had unknown lymph node status with no follow-up. All cases were immunoreactive with CD20 and negative with CD3. Bcl-2 was immunoreactive in 11/18 cases, bcl-6 in 15/15, CD10 in 14/17, CD43 in 2/16 (both were CD10 immunoreactive) and CD5 in 1/15 (it was also bcl-6 immunoreactive). Eight of 18 cases were monoclonal for IgH. Three of 17 showed the presence of t(14;18). FISH was positive in 4 cases for trisomy 3 ranging from 16 to 22% (12% threshold). Follow-up showed no evidence of disease in 14/17 patients (4 to 137 mos). 3/17 patients are alive with disease (17 to 100 mo), and no patients died of disease.

Primary cutaneous follicle center cell lymphoma

The exact classification of primary cutaneous follicle center cell lymphomas (FCCLs) has been the subject of ongoing debate. In the classification of cutaneous lymphomas proposed by the European Organization for Research and Treatment of Cancer (EORTC)-Cutaneous Lymphoma Project Group, cutaneous follicle center cell lymphoma (FCCL) is defined as a proliferation of centrocytes and centroblasts showing a diffuse pattern of growth in the great majority of cases, and presenting only rarely a true follicular pattern. CD10 and Bcl-2 are usually not expressed by neoplastic cells, and the t(14:18) is absent. By contrast, nodal follicular lymphoma is a tumor with a follicular pattern, characterized by the proliferation of CD10+, Bcl-2+ follicular cells, and by the presence of the t(14;18) in most cases. In this review we outline the clinicopathologic, phenotypic, and molecular features of primary cutaneous FCCL, reviewing criteria for diagnosis and differential diagnosis of this peculiar variant of cutaneous B-cell 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.

Primary cutaneous large B-cell lymphoma: the relation between morphology, clinical presentation, immunohistochemical markers, and survival

The histogenesis, morphology, immunophenotype, and clinical behavior of cutaneous large B-cell lymphomas (CLBCL) are largely a matter of controversy. We performed an investigation to determine whether CLBCL have features that differentiate them from other large B-cell lymphomas and whether CLBCL is itself a heterogeneous group. To this end, we reviewed the main characteristics of a series of 32 cases of LBCL found in the skin. We reviewed the clinical findings and paraffin sections of the tumors from these 32 patients. The immunohistochemical study performed included p53, MIB1, Bcl2, Bcl6, and CD10 markers. We carried out statistical analysis of these data (univariate and multivariate), seeking an association between the features of the tumors and clinical outcome, as defined by failure-free survival time. Only one patient died as a consequence of the lymphoma. Nevertheless, the accumulated probability of survival without failure at 48 months was 0.46. The number, type, and localization of the lesions were not associated with variations in either survival or failure-free survival. The expression of p53 was negative in this group of CLBCL, whereas Bcl-2 expression or localization in the lower leg did not relate to any other significant feature. Histologic examination of the cases disclosed three different groups: Grade III follicular lymphomas (FLs), monomorphous large B-cell lymphomas (LBCL type I), and LBCL with an admixed component of small B-lymphocytes (LBCL type II). Grade III FL (11 cases) tended to be found in the head and neck and showed CD10 expression in a majority of cases. A higher probability of lymph node relapses was associated with cases located in the head and neck and with CD10+ tumors. Cutaneous large B-cell lymphomas are indolent tumors, but follow an insidious course. Our data support the interpretation that CLBCL is a heterogeneous condition; comprises some LBCL derived from CD10+ germinal center cells which manifests more frequently as tumors in the head and neck region, with an increased probability of relapse in lymph nodes [1] and has some distinctive morphologic features. The existence of a component of small B-cells within the other CLBCL could lend support to the theory that some of these tumors, more than arise de novo, may have originated in preexistent small B-cell lymphomas, but no firm evidence of this is provided in this study.

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.

Mainly unmutated V(H) genes rearranged in B cells forming germinal centers in a cutaneous pleomorphic T-cell lymphoma

B cells in skin lesions of a pleomorphic cutaneous T-cell lymphoma with reactive germinal center hyperplasia were analyzed for their immunoglobulin V(H)DJ(H) gene rearrangements by micromanipulation and single cell polymerase chain reaction (PCR) analysis. In B lymphocytes located in germinal center-like structures, we found in 11/16 different V(H)DJ(H) rearrangements completely unmutated VH genes, suggesting that those cells did not undergo antigen-driven selection. Two V(H) genes showed more than 98% germ-line identity. In only three cells V(H) segments were somatically mutated to a higher extent, but two of these rearrangements were non-productive. These results differ markedly from what we have previously detected in B cells present in mycosis fungoides, another entity of cutaneous T-cell lymphomas where the Ig gene repertoire resembles the situation in peripheral blood with a significantly higher proportion of mutated V(H) genes. When investigating the large atypical B cells strongly expressing CD30 which were detected within the T-cell zone outside the germinal centers, we found again, in most cases, that the rearranged VH genes were completely unmutated. The B cells were of polyclonal origin. Due to this comparable Ig gene repertoire and mutational pattern, we suggest that these cells descend from the germinal center centroblasts which migrated into the T-cell zone and obviously became stimulated to express the CD30 marker. The micromanipulation technique and molecular analysis on the single cell level may provide an important input into our understanding of the mechanisms of immune regulation in cutaneous lymphomas.

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.

Immunohistochemistry: a prognostic as well as diagnostic tool?

The assessment of proliferating cell populations has been used to aid in the differentiation of benign from malignant neoplasms, and it has been hoped that assessment of proliferation markers and oncogenic determinants holds information regarding prognosis. Various markers, including Ki-67, p53 protein, bcl-2, and proliferating cell nuclear or paraffin-embedded tissue. These determinants may prove useful in understanding the biology of certain neoplasms and may carry prognostic information that influences clinical management. Results in this developing field must always be interpreted in the clinical and histological context. This article reviews the applicability of some commonly available markers to selected skin disorders.