Cutaneous presentation of nasal/nasal type T/NK cell lymphoma: clinicopathological findings of four cases

Epstein–Barr virus (EBV)-associated T/natural killer (NK) cell lymphoma mainly shows nasal lesions, and has recently been shown to be associated with cutaneous T-cell lymphoma (CTCL). The detailed features of CTCL nasal metastasis have yet to be elucidated. We report clinicopathological findings for four cases of cutaneous T/NK cell lymphoma with metastasis to the nose. The four patients presented progressive involvement of nasal lesions of CTCL, an aggressive course and poor outcome. Their pathological and immunohistological findings were consistent with peripheral T/NK cell neoplasm and, in three of four cases, EBER-1 were apparently detected in lymphoma cells by in situ hybridization, and two of four cases were also positive for TIA-1. The polymerase chain reaction (PCR) results showed the identical band from the skin and nasal lesions of the two patients. We also reviewed the cases of similar clinical course and attempted to elucidate clinical, pathological, immunological and genotypic features. The 10 reported cutaneous T/NK cell lymphomas with nasal metastasis revealed a poor prognosis (nine of 10 died at 3–108 months). Six cases of nine showed a positive reaction to EBV, and six cases revealed T-cell receptor β or -γ rearrangement. These findings suggest that most cutaneous T/NK cell lymphoma with nasal metastasis are similar to nasal T-cell lymphoma associated with EBV infection. This type of cutaneous T/NK cell lymphoma likely to involve nasal lesions and skin cases seemed to have a poor prognosis.     

gamma delta T-cell lymphoma of the skin: a clinical, microscopic, and molecular study

BACKGROUND: Only a few cases of primary gamma delta cutaneous T-cell lymphoma (CTCL) have been reported. We encountered 3 cases of this rare condition. OBJECTIVES: To characterize gamma delta CTCL by clinical, microscopic, and molecular methods and to investigate the role of Epstein-Barr virus (EBV) infection in its pathogenesis. DESIGN: Patients were evaluated by clinical examination, and biopsy specimens of lesional skin were examined by light microscopy and immunohistochemistry. Polymerase chain reaction amplification for T-cell receptor gamma gene rearrangements and in situ hybridization for EBV were performed on 3 biopsy specimens. SETTING: National Institutes of Health, a tertiary referral center. PATIENTS: Individuals with a clinical and histologic diagnosis of primary gamma delta CTCL. OUTCOME MEASURES: Clinical, light microscopic, and immunohistochemical features, and the presence of T-cell rearrangement and EBV RNA in biopsy specimens. RESULTS: Patients exhibited multiple plaques, tumors, and/or subcutaneous nodules primarily distributed over the extremities. Individuals exhibited an aggressive clinical course with resistance to multiagent chemotherapy and radiation. Microscopic examination revealed epidermotropism in 2 cases, a dermal infiltrate in all 3 cases, and subcutaneous involvement in 1 case. Immunohistochemical studies showed the presence of CD3(+)TCR delta(+) in 3 patients, CD8(+)in 1, and CD4(+), CD20(+), CD56(+), and beta F1(+) in none. All 3 cases exhibited an activated cytotoxic T-cell phenotype positive for T-cell intracellular antigen 1, perforin, and granzyme B. A clonal T-cell receptor gamma chain gene rearrangement was detected in all 3 cases by polymerase chain reaction. In situ hybridization was negative for EBV sequences in all 3 cases. CONCLUSION: gamma delta Cutaneous T-cell lymphomas are EBV-negative lymphomas that express a mature cytotoxic phenotype and have an aggressive clinical behavior. Arch Dermatol. 2000;136:1024-1032     

Characteristics of cutaneous lymphomas in Osaka, Japan (1988-1999) based on the European Organization for Research and Treatment of Cancer classification

Based on accumulating information, European investigators proposed a new classification for primary cutaneous lymphomas known as the European Organization for Research and Treatment of Cancer (EORTC) classification. The clinical utility of this classification in Japanese cases has not been evaluated. Material from 65 patients with cutaneous lymphomas (48 with primary disease and 17 with secondary disease) who were admitted to Osaka University Hospital during the period 1988 through 1999 was reviewed. Immunohistochemical analysis was performed in all cases. Cutaneous T-cell lymphoma (CTCL) comprised mycosis fungoides (15 cases), Sézary syndrome (1 case), lymphomatoid papulosis (5 cases), large cell CTCL (13 cases), pleomorphic small- or medium-sized CTCL (2 cases), and cutaneous natural killer /T-cell lymphoma (4 cases). B-cell lymphomas comprised 7 cases of follicle center cell lymphoma and 1 case of diffuse large B-cell lymphoma of the leg. Each category of disease in the EORTC scheme showed its characteristic features in our series. Five of 13 large cell CTCL cases were positive for CD30, and 5 were negative. The 5-year survival rate of patients with large cell CTCL CD30+ disease was 100% and that of patients with CD30- disease was 0%. (p > 0.1). Only 1 of 7 CTCL cases expressing CD30 was ALK-1+, and all 7 cases showed a favorable clinical course. The EORTC classification is effective in dealing with Japanese cases of cutaneous lymphomas.     

儿童皮肤非何杰金淋巴瘤与EB病毒的相关性研究

目的研究EB病毒与儿童皮肤非何杰金淋巴瘤(nonhodgkin’lymphoma,NHL)发病的关系。方法采用原位杂交法对36例儿童皮肤NHL的标本进行EB病毒编码的小分子寡核苷酸(Epstein-Barr viralencoded RNA,EBER)检测。结果36例中EBER阳性7例(19.4%),其中皮下脂膜炎样T细胞淋巴瘤(subcutaneous panniculitis-like T-celllym-phoma,SPTCL)5例;外周T细胞淋巴瘤、Burkitt’s瘤各1例;CD30+间变型大细胞淋巴瘤、T淋巴母细胞性淋巴瘤均未见阳性表达。结论EB病毒感染与皮下脂膜炎样T细胞淋巴瘤可能有关,与T淋巴母细胞性淋巴瘤、CD30+间变型大细胞淋巴瘤关系不明显,其与累及皮肤的Burkitt’淋巴瘤的关系有待进一步证实。     

Primary cutaneous T-cell lymphoma occurring after organ transplantation

Lymphoma occurring after organ transplantation has been well described. The majority of cases are B-cell lymphomas and are usually associated with Epstein-Barr virus. Only a minority of posttransplant lymphomas are of T-cell origin, and primary cutaneous T-cell lymphoma (CTCL) is extremely rare. In this article, we report a case of cutaneous peripheral T-cell lymphoma, pleomorphic CD30+ large-cell type, and review the literature relating to posttransplant primary CTCL. Of the 23 cases of posttransplant primary CTCL, 5 patients had erythrodermic disease, and 8 had primary cutaneous anaplastic large cell lymphoma. In addition, there are two cases of mycosis fungoides, one case of subcutaneous panniculitis-like T-cell lymphoma, one case of CD30+ lymphomatoid papulosis, and 6 cases of peripheral T-cell lymphoma, of which 3 were CD30+ large cell lymphomas. Seventeen cases had renal transplants and the majority received both cyclosporine and azathioprine. No consistent viral association was noted among these cases. The sex ratio was 18:5 (male/female), and the mean age at diagnosis was 53 years. Mean time from transplantation to diagnosis is 6.4 years and mean survival time from diagnosis is 14.5 months. The prognoses normally associated with particular subsets of CTCL do not apply in the posttransplant setting.     

Unlikely role of Epstein-Barr virus in the pathogenesis of primary cutaneous CD30+ anaplastic large cell lymphoma

BACKGROUND: Primary cutaneous CD30+ anaplastic large cell lymphoma (ALCL) is a rare subset of cutaneous lymphoma, with a much better prognosis than its nodal counterpart. The pathogenesis of both nodal and primary cutaneous CD30+ ALCL is largely unknown but experimental data support the hypothesis that the Epstein-Barr virus could play a role in the nodal subset. OBJECTIVE: To evaluate the involvement of Epstein-Barr Virus (EBV) in primary cutaneous CD30+ ALCL by searching for both nucleic acids and EBV proteins in cutaneous lesions. SETTING: Two University Hospitals in Southern France (secondary referral hospitals). PATIENTS: Eight consecutive patients with typical primary cutaneous CD30+ anaplastic large cell lymphoma were studied. METHODS: Search for the presence of DNA, RNA and EBV proteins in cutaneous lesions by PCR, in situ hybridization and immunohistochemistry. RESULTS: EBV DNA and RNA was identified in only one lesion of primary cutaneous CD30+ ALCL and in none of the normal adjacent skin samples. In situ hybridization and immunohistological studies were consistently negative in all samples. Conclusion: These results do not support an early role of EBV in the oncogenetic pathogenesis of primary cutaneous CD30+ ALCL.     

Detection of Epstein-Barr virus and human herpesvirus 7 and 8 genomes in primary cutaneous T- and B-cell lymphomas

BACKGROUND: Several studies have investigated the possible involvement of viral agents, particularly herpesviruses, in primary cutaneous lymphoma (PCL). OBJECTIVES: Our aim was to screen for the presence of human herpesvirus 7 (HHV-7) and 8 (HHV-8) genomes in samples of PCL, and to determine if their presence was independent of Epstein-Barr virus (EBV). METHODS: Screening was performed using polymerase chain reaction assay in 64 skin samples from historical lesional tissues with PCL. RESULTS: Only nine cases showed positivity for HHV-7: four of 29 mycosis fungoides (MF), two of four CD30-positive large-cell cutaneous T-cell lymphoma (CTCL), two of 12 follicle centre cutaneous B-cell lymphoma (CBCL) and one of nine marginal zone CBCL. Fifteen cases tested positive for EBV: seven of 29 MF, two of four pleomorphic small/medium sized CTCL, three of three angiocentric CTCL, one of 12 follicle centre CBCL and two of nine marginal zone CBCL. All cases were uniformly negative for HHV-8. No simultaneous positivity was found for EBV and HHV-7. Controls tested negative for all viruses. CONCLUSIONS: The findings indicate that EBV, HHV-7 and HHV-8 seem not to be involved in the pathogenesis of PCL.     

Indolent CD8-positive T-cell lymphoid proliferation of the ear: a report of two cases

The current classification of primary cutaneous T-cell lymphoma (CTCL) of the World Health Organization (WHO) includes primary cutaneous CD8-positive aggressive epidermotropic cytotoxic T-cell lymphoma as a provisional entity awaiting cumulative data. Recent reports identify CD3/CD8-positive clonal T-cell lymphoid proliferations arising in the ear and nose that behave indolently and therefore defy currently established subclassification. Here, we report two cases of clonal CD8-positive/granzyme-B-negative T-cell lymphoid proliferations that arose in the ear and behaved indolently. Collectively, these cases suggest that an additional category of cutaneous indolent CD8-positive T-cell lymphoma may be necessary among the existing classification schemes.     

Detection of Epstein-Barr virus in primary cutaneous amyloidosis

To determine the association of Epstein-Barr virus (EBV) with primary cutaneous amyloidosis (PCA), a retrospective study was conducted on skin tissue from 27 Chinese patients with lichen amyloidosus and macular amyloidosis. In situ hybridization with oligonucleotide probes was used to detect the expression of EBV-encoded RNAs (EBERs). Eleven of 27 cases (40.7%) were found to contain the EBV genome. No EBV genome was detected in the skin of the control groups, including three cases of secondary cutaneous amyloidosis, two cases of primary systemic amyloidosis, and four cases of lichen simplex chronicus. Our study showed no correlation between the presence of EBV in PCA patients and the patients'age, sex, clinical type or severity of the skin lesions. Although our results suggest that EBV may be associated with some cases of PCA, the true aetiological role of EBV in PCA remains unknown.     

Cutaneous peripheral T-cell lymphoma of cytotoxic phenotype mimicking extranodal NK/T-cell lymphoma

Cutaneous peripheral T-cell lymphoma unspecified is a rare neoplasm that is infrequently associated with Epstein-Barr virus (EBV) infection. In contrast, extranodal natural killer (NK)/T-cell lymphoma, although also rare, is known to be strongly associated with EBV and occurs most commonly in the nasal region. We report the case of a 55-year-old male who presented with fever and an indurated cutaneous plaque with ulceration. This cutaneous neoplasm showed diffuse dermal lymphomatous infiltration and tumor necrosis, with neoplastic cells expressing CD2, cytoplasmic CD3 (CD3ε), CD8, CD16, CD30, T-cell intracellular antigen-1, and granzyme B but not CD56, BF1, or T-cell receptor (TCR) δ1. Furthermore, the tumor cells were noted to be diffusely positive for EBV by in situ hybridization. A monoclonal TCR gene rearrangement was demonstrated. The disease showed an aggressive clinical course, and the patient died within 3 weeks of diagnosis without complete staging or chemotherapy. According to the 2005 World Health Organization/European Organization for Research and Treatment of Cancer scheme for cutaneous lymphoma and the 2008 WHO classification for lymphoid neoplasms, our case would have been classified as a nasal type extranodal NK/T-cell lymphoma with T-cell lineage. However, the expressions of CD8 and CD16, in addition to a monoclonal TCR gene rearrangement, are unusual findings in NK/T-cell lymphoma, and we believe such a phenotype/genotype should be more appropriately classified as an EBV-positive peripheral T-cell lymphoma, unspecified with a cytotoxic phenotype. Detailed clinicopathologic and molecular studies of similar cases may shed light on the prognostic impact of NK vs. T-cell lineage on extranodal NK/T-cell lymphomas.     

牛痘样水疱病样皮肤淋巴瘤与慢性活动性EB病毒感染的关系

目的 报道6例牛痘样水疱病样皮肤淋巴瘤,并研究其与慢性活动性EB病毒感染的关系.方法 临床病理分析、皮损免疫组织化学染色、血清学分析、EB病毒编码RNA原位杂交、外周血EB病毒DNA测定.结果 6例患者皮损均为反复发作的丘疹、丘疱疹、坏死、痘疮样瘢痕,其中4例还伴有程度不同的颜面、手足水肿.所有患儿均有长期间断发热等症状.皮损病理可见表皮多房性水疱,真皮全层大量淋巴细胞浸润,细胞形态异形,可见病理分裂象.4例皮损病理免疫组化染色,可见大量CD56阳性细胞,散在的CD3和CD45RO阳性细胞,T细胞内抗原-1和粒酶B染色阳性,诊断为牛痘样水疱病样皮肤NK/T细胞淋巴瘤;2例组化染色CD3和CD45RO阳性,CD56阴性,诊断为牛痘样水疱病样皮肤T细胞淋巴瘤.6例皮损均可见EB病毒编码RNA原位杂交阳性肿瘤细胞,血清学检查EB病毒衣壳抗原IgG抗体滴度升高,其中2例滴度为1:5120,2例为1:2560,2例为1:1280;2例患者外周血EB病毒DNA拷贝数高于正常.6例患儿均证实患有慢性活动性EB病毒感染.结论 牛痘样水疱病样皮肤淋巴瘤主要表现为颜面手足肿胀、水疱、痘疮样瘢痕,病理表现主要为真皮异形淋巴细胞浸润和血管中心坏死,免疫表型以NK/T型多见.慢性活动性EB病毒感染与该型淋巴瘤发病密切相关.     

Blastic natural killer cell and extranodal natural killer cell-like T-cell lymphoma presenting in the skin: report of six cases from the UK

BACKGROUND: Some lymphomas express natural killer (NK)-cell markers such as the neural cell adhesion molecule, which is recognized by the CD56 antibody. These lymphomas may present in the skin, but do not represent a homogeneous group. The new World Health Organization classification of lymphoma/leukaemia recognizes several types of NK/T-cell neoplasm, including blastic NK-cell lymphoma, which characteristically presents with cutaneous lesions. OBJECTIVES: To describe the clinical, pathological and molecular features in six cases of CD56+ lymphoma with cutaneous presentation. METHODS: The clinical, histopathological and immunophenotypic features of six patients were reviewed. In addition, in situ hybridization (ISH) to identify Epstein-Barr virus (EBV) mRNA, and polymerase chain reaction analysis to identify the presence of a clonal population of T cells or B cells were performed on lesional skin. RESULTS: All patients presented with widespread nodules and plaques, which in five cases were a characteristic purple colour. Four patients developed disseminated disease, three with neurological involvement. These four patients died between 14 and 46 months following diagnosis (median 30 months). In four of six cases the histopathological and immunohistological features were in keeping with a blastic NK-cell lymphoma. No clonal immunoglobulin heavy chain (IgH) or T-cell receptor (TCR) gene rearrangement was detected in the four cases consistent with an origin from NK cells. A further case fitted the criteria for an extranodal NK/T-cell lymphoma of nasal type and was also the only case to show evidence of EBV mRNA by ISH. A clonal T-cell population was identified in the final case. This patient also exhibited molecular evidence of a clonal B-cell population and a t(14;18) translocation confirmed by sequence analysis. CONCLUSIONS: Our data confirm that NK-cell lymphomas presenting in the skin are a heterogeneous group, and that in the U.K., blastic NK-cell lymphoma is more common than extranodal NK/T-cell lymphoma of nasal type. These lymphomas pursue an aggressive course, with rapid development of disseminated disease, and resistance to chemotherapy. Detailed immunophenotyping is needed to distinguish the different types. Our molecular data indicate that blastic NK-cell lymphoma cases lack clonal TCR/IgH gene rearrangements consistent with an NK-cell origin. Our ISH findings indicate that EBV plays a pathogenetic role only in extranodal NK/T-cell lymphoma of nasal type.     

CD30-positive cutaneous T-cell lymphoma with concurrent solid tumour

Extranodal CD30+ T-cell lymphomas seldom carry classical t(2;5) translocation and are usually anaplastic large cell lymphoma kinase protein negative. They cover a wide spectrum of histological and clinical behaviour. The prognosis of CD30+ cutaneous T-cell lymphoma (CTCL) is good in the absence of nodal primary or disseminated disease. These lesions can undergo spontaneous regression, and overlap with the group of lesions of lymphomatoid papulosis. Although an increased incidence of solid tumours has been reported in patients with CD30+ non-Hodgkin lymphoma of the skin, reports of concurrent malignancies are rare in CD30+ CTCL. We report two patients with CD30+ CTCL who, respectively, had concurrent disseminated gastric carcinoma and bilateral ovarian teratoma. Despite an aggressive clinical and histological appearance, both cases ran favourable clinical courses. The CTCL responded completely to chemotherapy in one patient, who eventually succumbed to gastric cancer. In the other patient, lesions regressed spontaneously after bilateral oophorectomy. A possible relationship between the lymphoma and the solid tumours is discussed.     

Regressing cutaneous lymphomas of T-cell and B-cell lineage

We report two cases of regressing cutaneous lymphoma. The first case is a CD30-positive T-cell lymphoma with immunogenetic evidence of clonality. The second case is a diffuse large-cell non-Hodgkin's lymphoma of B-cell lineage in which clonality was established by immunogenetic analysis and in situ hybridization for light-chain mRNA.     

Nasal‐type extranodal natural killer/T‐cell lymphoma presenting with extensive leg ulcers

Primary cutaneous T‐cell lymphomas are rare and can be difficult to classify precisely. We present a case of extranodal natural killer (NK)/T‐cell lymphoma in a previously healthy, immunocompetent man who presented with extensive necrotic leg ulcers and disseminated skin nodules. Immunohistochemical studies revealed that the tumour cells were positive for CD3, CD30, granzyme B and T‐cell intracellular antigen‐1, and negative for CD5 and CD56, with positive staining for Epstein–Barr virus (EBV) RNA on in situ hybridization. A diagnosis of extranodal NK/T‐cell lymphoma was made, based on the presence of cytotoxic granules and positive EBV RNA staining. The patient was treated with a regimen of chemotherapy comprising corticosteroids, intravenous methotrexate, ifosphamide, L‐asparginase and etoposide with initial response.     

Detection of Epstein-Barr virus genome in primary cutaneous T and B cell lymphomas and pseudolymphomas

The Epstein-Barr virus (EBV) genome has recently been identified in Hodgkin's disease (HD) and nodal non-Hodgkin's lymphomas (NHL). In order to elucidate the possible aetiopathogenetic role of EBV in benign and malignant lymphoproliferative disorders we investigated skin specimens from 24 patients with a primary cutaneous lymphoproliferative disorders (10 T-cell lymphomas 6 B-cell lymphomas and 8 pseudolymphomas) and from 22 normal individuals for the presence of EBV DNA using the polymerase chain reaction (PCR) technique and in situ hybridization (ISH) on formalin-fixed paraffin-embedded tissue sections. EBV DNA was identified by PCR in one of two cases of mycosis fungoides, in one of seven cases of pleomorphic T-cell lymphomas, in one case of centro-blastic (CB) lymphoma of six B-cell lymphomas, and in three of eight pseudolymphomas. The EBV genome was also found in 2 of 22 specimens of normal skin. The small EBV-encoded nuclear RNAs, EBERs, were not detected in any PCR-positive sample by ISH. Based on our PCR and ISH findings, EBV does not seem to play a significant role in the development of cutaneous lymphomas.     

Rearranged T-cell receptor gene and positive Epstein-Barr virus-encoded nuclear RNA in an extranodal NK/T-cell lymphoma with cutaneous manifestation only: case study

Natural killer (NK)/cytotoxic T-cell lymphoma, a new type of cutaneous neoplasm, has been described recently in the World Health Organization/European Organization for Research and Treatment of Cancer classification for cutaneous lymphomas. We report an 11-year-old boy who had had erythematous plaques and blisters on his face and hands for 4 years and infiltrating plaques and necrosis on his extremities for 4 months. Routine clinical and laboratory examinations found no primary nasal involvement. Biopsies taken from nasal mucosa and skin showed that the tumour only involved dermis and subcutaneous tissue, and the infiltrated lymphohistiocytic tumour cells were CD56+, TIA+, CD45RO+ and CD30+. In situ hybridization for EBV-encoded nuclear RNA was positive. Clonal T-cell receptor-gamma2 gene rearrangement was positive. A diagnosis of extranodal NK/T-cell lymphoma, nasal type, was made. This is a rare case, with slow course and survival for >51 months with the presentation only occurring in the skin.     

Relative frequency of the different types of cutaneous T cell and natural killer cell lymphomas in Korea based on the proposed WHO classification and the EORTC classification

The R.E.A.L. classification was largely adopted recently by the proposed WHO classification. The usefulness of this classification in cutaneous T cell and natural killer (NK) cell lymphomas in Korea was evaluated compared to that of the European Organization for Research and Treatment of Cancer (EORTC) classification. Overall, 78 patients with cutaneous T cell and NK cell lymphomas were diagnosed in Asan Medical Center in the 1990's. The clinical records, slides of H&E and immunohistochemical stainings were reviewed. By the proposed WHO classification, mycosis fungoides (20 cases), lymphomatoid papulosis (13 cases), nasal type NK/T-cell lymphoma (10 cases), CD30+ anaplastic large cell lymphoma (8 cases), subcutaneous panniculitis-like T-cell lymphoma (6 cases), peripheral T-cell lymphoma, unspecified (3 cases), Sézary syndrome (1 case) and blastic NK cell lymphoma (1 case) comprised the primary cases. Secondary or undetermined cases included peripheral T-cell lymphoma, unspecified (10 cases), nasal type NK/T-cell lymphoma (5 cases), and angioimmunoblastic T-cell lymphoma (1 case). EORTC classification for cutaneous T cell and NK cell lymphomas did not include nasal and nasal type NK/T-cell lymphomas, unspecified non-pleomorphic T-cell lymphoma, undetermined cases among primary or secondary ones and some rare types of skin lymphomas which can be classified by WHO. The WHO classification is more useful for skin lymphomas in Korea since it encompassed all the various types of skin T cell and NK cell lymphomas in Korea.     

Expression of Fas and Fas-ligand in primary cutaneous T-cell lymphoma (CTCL): association between lack of Fas expression and aggressive types of CTCL

BACKGROUND: Fas (CD95; APO-1) is a transmembrane protein that mediates apoptosis upon cross-linking with Fas-ligand (Fas-L). Interaction of Fas-L expressed by cytotoxic T cells with Fas-expressing tumour cells plays an important part in antitumour immune responses. OBJECTIVES: We aimed to investigate Fas and Fas-L expression in frozen and paraffin-embedded material from a large group of patients with cutaneous T-cell lymphoma (CTCL). METHODS: Immunostaining with monoclonal antibodies against Fas and Fas-L was performed in material from 23 patients with mycosis fungoides (MF), 10 with lymphomatoid papulosis (LyP), 10 with CD30-positive primary cutaneous large T-cell lymphoma (LTCL) and nine with CD30-negative LTCL. The results were correlated with the type and stage of CTCL and clinical features. RESULTS: Expression of Fas by the large majority of the neoplastic T cells was observed in 15 of 15 cases of plaque-stage MF, 10 of 10 cases of LyP and 10 of 10 cases of CD30-positive LTCL, but only in four of 12 cases of tumour-stage MF and two of nine cases of CD30-negative LTCL. In three of four MF patients in whom both plaques and tumours could be studied, a significant decrease in Fas expression was observed with progression from plaque-stage to tumour-stage disease. Fas-L was expressed by > 50% of the neoplastic T cells in 46 of 56 biopsies, and no clear relationship with type of CTCL and clinical behaviour was observed. CONCLUSIONS: This study demonstrates loss of Fas expression in aggressive types of CTCL, but not in indolent types of CTCL. These data suggest that loss of Fas receptor expression may be one of the mechanisms that allow tumour cells to escape an effective immune response, and may contribute to the unfavourable prognosis of some types of CTCL.