Studies of immunoglobulin and T cell receptor gene rearrangement in cutaneous B and T cell lymphomas

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.

The polymerase chain reaction in the diagnosis of early mycosis fungoides

The earliest or patch stage of mycosis fungoides may present diagnostic difficulty both clinically and pathologically. The present study of the polymerase chain reaction (PCR) as a diagnostic tool in early mycosis fungoides was therefore undertaken, using a rapid PCR method for the detection of gamma- and beta-chain T-cell receptor (TCR) gene rearrangements in routine formalin-fixed, paraffin-embedded histological sections. Forty-two biopsies were studied from 26 patients with mycosis fungoides. Twenty-three skin biopsies with a clinicopathological diagnosis of early, or patch stage, mycosis fungoides were investigated. Of these, 18 (78 per cent) showed TCR-gamma or both beta- and gamma-chain TCR gene rearrangements. TCR gene rearrangements were shown in seven of the 14 plaque stage lesions (50 per cent) and also in the single case of tumour stage disease. Where gene rearrangements were identified, these were identical in all biopsies from an individual patient, irrespective of the site of the lesion, the disease stage, or the time lapse between the biopsies. The PCR is therefore a highly sensitive technique, which can be performed on routine pathological material, in cases where the diagnosis of early mycosis fungoides cannot be made with certainty on conventional histopathological and immunohistochemical grounds.

Lymphoma versus pseudolymphoma of the skin: gene rearrangement study of 21 cases with clinicopathologic correlation

BACKGROUND

Diagnosis of cutaneous lymphoma in the absence of systemic lymphoma may be difficult. Reactive lymphoid lesions can mimic lymphoma clinically and histologically and have been designated pseudolymphomas.

OBJECTIVE

Our purpose was to analyze lymphoid gene rearrangements in cutaneous lymphoproliferative lesions and to correlate these findings with the histologic, immunophenotypic, and clinical profile.

METHODS

We examined 21 cases of lymphoproliferative lesions that developed in skin and performed molecular rearrangement analysis of T-cell receptor and immunoglobulin genes. We examined identical tissues by histologic and immunophenotypic criteria and conducted follow-up clinical evaluation of all patients.

RESULTS

Clonal rearrangements of immunoglobulin (seven cases) or T-cell receptor (two cases) gene were detected in 9 of 21 patients. No specific histologic or immunophenotypic feature was consistently associated with a clonal lymphoid gene rearrangement. Systemic lymphoma developed in one patient in whom a clonal rearrangement within the immunoglobulin gene was identified.

CONCLUSION

Gene rearrangement analysis may be helpful in differentiating primary cutaneous lymphoma from pseudolymphoma. The chronic clinical course of patients with clonal lymphoid gene rearrangements supports a lack of correlation between clonality and biologic aggressiveness.

T-cell receptor gene rearrangement analysis: cutaneous T cell lymphoma, peripheral T cell lymphoma, and premalignant and benign cutaneous lymphoproliferative disorders

T-cell receptor gene rearrangement analysis is a useful technique to detect clonality and determine lineage of lymphoid neoplasms. We examined 103 patients with mycosis fungoides, Sézary syndrome, peripheral T cell lymphoma, potentially malignant lymphoproliferative disorders including pre-Sézary syndrome, large plaque parapsoriasis, lymphomatoid papulosis and follicular mucinosis, and various benign inflammatory infiltrates. A clonal rearrangement was detected in skin samples in 20 of 24 patients with mycosis fungoides and in peripheral blood samples in 19 of 21 patients with Sézary syndrome. A clonal population was also detected in seven of eight cases classified as peripheral T cell lymphoma. The potentially malignant dermatoses tended to have clonal rearrangement, with the exception of large plaque parapsoriasis, and further follow-up is needed to correlate clonality with the disease course. These studies demonstrate the value of molecular genetics as an adjunct to morphology in the examination of patients with cutaneous lymphoproliferative disease.

Cutaneous lymphomas of phenotypically undetermined lineage: contribution of genotypic analysis

Genotypic analyses were performed in six primary cutaneous lymphomas whose lineage could not be assessed on the basis of histologic and phenotypic data. By immunophenotyping, these neoplasms expressed leukocyte common antigen and HLA-DR but did not show consistent immunostaining for B-cell or T-cell differentiation antigens. Expression of nonspecific histiocytic markers such as lysozyme and alpha 1-antitrypsin was found in three cases. By genotyping, three cases retained a germline configuration and immunoglobulin gene rearrangement was observed in one case, T-cell receptor gene rearrangement was found in one case, and both types of rearrangements in one case. Of the three patients in whom gene rearrangements were noted, two rapidly died and the other patient, with a dual genotype, is still alive 15 years after diagnosis. The three patients without gene rearrangements are alive and well after a mean follow-up of 2.5 years. It appears that cutaneous lymphomas with an uncertain phenotype include at least some cases of authentic B-cell or T-cell lymphomas. The germline configuration that we observed in cases with a chronic course remains difficult to explain. It may be related to a low malignancy form of histiocytic lymphoma, an atypical polyclonal hyperplasia, or even a low-grade lymphoma arising from a primitive cell without established commitment to either B- or T-cell lineage.

Gene rearrangement analysis in lymphoid neoplasia

Current uses for gene rearrangement analysis in clinical dermatology are listed in Table 3. This technique is useful for determining the existence of clonal populations within a background of polyclonal lymphoid cells; therefore, it is helpful in the diagnosis and staging of patients with CTCL and PTCL. Although dual genotypes do occur, this technique is usually capable of determining lineage in a clonal lymphoid infiltrate and elucidating and characterizing the etiopathogenesis of certain neoplasms. On the basis of this review of the literature and our own experience, we conclude that gene rearrangement analysis shows great promise for monitoring response to therapy and detecting progression or relapse in patients with CTCL and PTCL. With the recent technology of PCR, it is possible to amplify specific sequences of DNA, detect molecular alterations in individual malignant T cells, and even identify exogenous retroviral gene sequences in tissues of patients with CTCL. Although gene rearrangement analysis has supported or established the clonal nature of lymphomatoid papulosis, pre-Sézary syndrome, granulomatous slack skin syndrome, and follicular mucinosis, the clinical significance of these findings is not yet clear. In the case of primary cutaneous B-cell lymphoma and its benign counterpart, B-cell pseudolymphoma, further investigation will be needed to determine the clinical significance of clonal rearrangements.