Pseudoclonality in cutaneous pseudolymphomas: a pitfall in interpretation of rearrangement studies

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.

No evidence of Borrelia in Cutaneous Infiltrates of B-cell lymphomas with a highly sensitive, semi-nested real time Polymerase chain reaction (PCR) targeting the 5S-23S intergenic spacer region (IGS)

BACKROUND

The role of Borrelia in the development of skin lymphomas has been under discussion for decades. A similar association has been shown for Helicobacter pylori and gastric lymphomas (MALT type). Nevertheless, few molecular studies investigated Borrelia in skin lymphomas and the results are controversial.

METHODS

We analysed 46 formalin-fixed, paraffin-embedded skin specimens of clincopathologically confirmed B-cell lymphomas (15 marginal zone lymphomas; 20 follicular lymphomas; 3 diffuse large B-cell lymphomas; 8 secondary cutaneous infiltrates) taken from 36 patients from Northern Germany, an endemic area for Borrelia. Fifteen pseudolymphomatous lesions of cutaneous Borreliosis served as control. Both groups were examined with a real time (rt) PCR and a semi-nested PCR targeting the 5S-23S intergenic spacer region (IGS). A multiplex PCR was used to investigate B-cell clonality in all lymphomatous infiltrates (Biomed Primers).

RESULTS

With both assays no B. burgdorferi-specific DNA was identified in any of the B-cell lymphomas, while all 15 Borreliosis specimens gave a positive PCR result in the semi-nested PCR protocol, 12 were also positive in the rt PCR (p<.01). All B-cell lymphomas showed monoclonal IgH-Rearrangement. Analysis of cutaneous B-cell lymphomas from available studies including ours (n=334) reveals an Odds ratio < 1.

CONCLUSION

While some previous studies suggested an association between B. burgdorferi and the development of cutaneous B-cell lymphomas in endemic areas, we were unable to confirm this in our patients, despite a highly sensitive Borrelia PCR assay. Our results including meta-analysis of previous studies question the need for antibiotic therapy in patients with cutaneous B-cell lymphomas.

Analysis of clonality in cutaneous B-cell lymphoma and B-cell pseudolymphoma using skin flow cytometry: Comparison of immunophenotyping and gene rearrangement studies

To identify clonal neoplastic cells in skin affected by B-cell lymphoma using skin flow cytometry (FCM) techniques, we investigated light-chain restriction using skin FCM with clonality assessed by polymerase chain reaction and light-chain restriction by in situ hybridization (ISH). We retrospectively analyzed 16 cases of B-cell lymphoma with cutaneous involvement: primary cutaneous diffuse large B-cell lymphoma, leg type (pcDLBCL-LT) (n = 7), DLBCL-not otherwise specified (DLBCL-NOS) (n = 6), primary cutaneous follicle center lymphoma (pcFCL) (n = 1), and follicular lymphoma (n = 2), as well as cutaneous B-cell pseudolymphoma (n = 9). Results of skin FCM light-chain restriction analyses were compared with immunoglobulin H (IgH) gene rearrangement and κ/λ ISH findings. Skin FCM detected light-chain restriction in 11 of 14 B-cell lymphoma patients but none of the B-cell pseudolymphoma patients. The sensitivity of skin FCM for distinguishing B-cell lymphoma and B-cell pseudolymphoma was 79%, and the specificity was 100%. Eleven of 13 B-cell lymphoma patients exhibited gene rearrangement (sensitivity 85%), whereas six of seven pseudolymphoma patients were negative (specificity 86%). ISH was positive in three of 16 B-cell lymphoma cases (sensitivity 19%) but none of the B-cell pseudolymphoma cases (specificity 100%). ISH sensitivity was 29% for pcDLBCL-LT, 17% for DLBCL-NOS, and 0% for pcFCL and follicular lymphoma. Skin FCM therefore appears to be more sensitive than ISH in detecting light-chain restriction in DLBCL and follicular lymphoma, and as sensitive as IgH gene rearrangement analysis in detecting clonality. Skin FCM is thus a promising diagnostic tool for identifying monoclonal neoplastic B-cell populations.

Clonality testing as complementary tool in the assessment of different patient groups with canine chronic enteropathy

Differentiation between canine chronic enteropathy (CCE) and intestinal lymphoma is a diagnostic challenge as histopathology might fail to yield unequivocal results. Detection of clonal rearrangements of the T-cell-receptor gamma (TCRG) chain and IG heavy chain (IGH) V-J genes offer a useful solution. In this retrospective study, histopathology samples of 35 CCE patients and 7 healthy Beagle dogs underwent clonality testing. Patients suffered either from inflammatory bowel disease (IBD), food responsive diarrhea (FRD) or protein loosing enteropathy secondary to IBD (PLE/IBD). Healthy Beagles served as controls (CO). Canine IBD activity index (CIBDAI) and histopathological WSAVA-grading differed significantly (p<0.001) between groups. CIBDAI improved significantly after appropriate therapy (p < 0.0001). Intestinal biopsies of all CO showed polyclonal patterns for B- and T-cell primers. All samples from CCE patients showed polyclonal patterns for the B-cell primers. Targeting TCRG, 4 patients showed a monoclonal or oligoclonal pattern of the lymphocytic infiltrates in the duodenum and/or colon. Clinical improvement was observed in all dogs. Although a small cell lymphoma cannot be excluded in view of the short follow up duration, a false positive result, in the sense of a canonical rearrangement or unspecific amplification due to a antigenic stimulation in a non-neoplastic inflammatory process is possible.

Next-generation sequencing of immunoglobulin gene rearrangements for clonality assessment: a technical feasibility study by EuroClonality-NGS

One of the hallmarks of B lymphoid malignancies is a B cell clone characterized by a unique footprint of clonal immunoglobulin (IG) gene rearrangements that serves as a diagnostic marker for clonality assessment. The EuroClonality/BIOMED-2 assay is currently the gold standard for analyzing IG heavy chain (IGH) and κ light chain (IGK) gene rearrangements of suspected B cell lymphomas. Here, the EuroClonality-NGS Working Group presents a multicentre technical feasibility study of a novel approach involving next-generation sequencing (NGS) of IGH and IGK loci rearrangements that is highly suitable for detecting IG gene rearrangements in frozen and formalin-fixed paraffin-embedded tissue specimens. By employing gene-specific primers for IGH and IGK amplifying smaller amplicon sizes in combination with deep sequencing technology, this NGS-based IG clonality analysis showed robust performance, even in DNA samples of suboptimal DNA integrity, and a high clinical sensitivity for the detection of clonal rearrangements. Bioinformatics analyses of the high-throughput sequencing data with ARResT/Interrogate, a platform developed within the EuroClonality-NGS Working Group, allowed accurate identification of clonotypes in both polyclonal cell populations and monoclonal lymphoproliferative disorders. This multicentre feasibility study is an important step towards implementation of NGS-based clonality assessment in clinical practice, which will eventually improve lymphoma diagnostics.

A review of canine B cell clonality assays and primer set optimization using large-scale repertoire data

Several molecular clonality assays have been developed to assess canine B cell proliferations. These assays were based on different sequence data, utilized different assay designs and employed different testing strategies. This has resulted in a complex body of literature and complicates evidence-based selection of primer sets. In addition, further refinement of primer sets is difficult because it is unknown how well current primer sets cover the expressed sequence repertoire. The objectives of this study were 1) to provide an overview of published IGH clonality assays that highlights key differences in assay design and testing strategy and 2) to propose a novel method for optimizing primer sets that leverages large-scale sequencing data. A review of previously published assays highlighted confounding factors that hamper a direct comparison of performance metrics between studies. These findings illustrate the need for a multi-institutional effort to harmonize veterinary clonality testing. A novel in silico analysis of primer sequences using a large dataset of expressed sequences identified shortfalls of existing primer sets and was used to guide primer optimization. Three optimized primer sets were tested and yielded qualitative sensitivity values between 80-90%. The qualitative sensitivity ranged from 1% to over 50% and was dependent on the size of the neoplastic clone and the sample DNA used. These findings illustrate that inclusion of high-throughput sequencing data for primer design can be a useful tool to guide primer design and optimization. This strategy could be applied to other antigen receptor loci or species to further improve veterinary clonality assays.

Immunohistochemical Profiling of Canine Intestinal T-Cell Lymphomas

Human enteropathy-associated T-cell lymphoma (EATL) is classified into 2 distinct subgroups based on their phenotypes (type I and type II). Canine intestinal T-cell lymphoma can be morphologically classified into large and small cell lymphomas (LCL and SCL, respectively). Their association with human EATL or immunohistochemical and biological features has not been well characterized. In this study, the immunohistochemical profiles of 17 cases of LCL and 33 cases of SCL were evaluated with markers used for human EATL classification. Morphologically, LCL was characterized by sheet-like proliferation of large to moderately sized neoplastic lymphocytes, with scant clear cytoplasm and pleomorphic, irregularly shaped nuclei containing distinctive nucleoli and scattered chromatin. In contrast, SCL was characterized by the proliferation of monomorphic small neoplastic lymphocytes, accompanied by infiltration of nonneoplastic plasma cells. Interestingly, 8 cases demonstrated mixed LCL and SCL morphologies. Granular cytoplasmic expression of granzyme B was observed in most LCL and SCL cases. Membranous expression of CD56 was demonstrated in only 2 of 17 LCL and 0 of 33 SCL cases. Coexpression of CD20 by neoplastic T cells was observed in more SCL cases (16/33; 48%) than LCL cases (1/17; 6%). The CD56-positive cells in 2 cases were negative for CD20. Although canine LCL shares common features with human EATL type I, canine SCL cells and human EATL type II differ in their immunophenotype. Canine intestinal T-cell lymphoma had a homogeneous immunophenotype regardless of cell morphology. The findings of this study may indicate large cell transformation of SCL rather than 2 distinct entities.

Primary cutaneous B-cell lymphoma: narrative review of the literature

Primary cutaneous B-cell lymphomas comprehend a group of lymphoproliferative disorders characterized by being monoclonal proliferations of B-cell primarily involving the skin. Despite being recognized as autonomous and distinct clinico-pathologic entities since the late 80s, their classification is still an ongoing matter of debate. At the moment, WHO classification recognizes three disorders: primary cutaneous marginal zone lymphoma, primary cutaneous follicle center lymphoma and primary cutaneous diffuse large b-cell lymphoma (leg type). Primary cutaneous diffuse large b-cell lymphoma (other) has been used to define rare cases which show histologically an infiltrate with diffuse pattern composed by large b-cell, but not fitting with criteria for follicle center lymphoma nor for primary cutaneous diffuse large b-cell lymphoma (leg type). Aim of this review was to briefly describe all recognized and provisional entities included in the primary cutaneous b-cell lymphomas and to discuss recent acquisitions that may influence their future classifications.

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.

IgA Antibodies Against Gliadin and Tissue Transglutaminase in Dogs With Chronic Enteritis and Intestinal T-Cell Lymphoma

Molecular clonality analysis of T-cell receptor (TCR) genes for diagnosing T-cell lymphoma is widely used in veterinary medicine. However, differentiating chronic enteritis (CE) from intestinal lymphoma is challenging because of the incompatibility between histopathologic and clonality analysis results. On the basis of findings that canine intestinal T-cell lymphoma and celiac disease share some common features, we conducted serologic examinations in combination with histopathologic and T-cell receptor clonality analyses in 48 dogs diagnosed with either CE or intestinal lymphoma. Immunoglobulin A (IgA) and immunoglobulin G (IgG) antibodies against gliadin and tissue transglutaminase (tTG) were quantitatively measured using ELISA. The conditions were classified according to the histopathologic diagnosis, clonality analysis, and combined histopathologic/clonality analysis. Histopathologic analysis showed that dogs with intestinal lymphoma were likely to have high levels of serum IgA antibodies against gliadin and tTG, and serum IgG antibodies against tTG. No correlation between the diagnosed groups and control group was observed in the results of the clonality analysis and histopathologic/clonality analysis. It is interesting that dogs with intestinal lymphoma had a higher serum IgA titer against gliadin and tTG than did dogs with CE. These results suggest an association between repetitive inflammatory stimulation by gliadin peptides and subsequent intestinal lymphoma in dogs.

A Literature Revision in Primary Cutaneous B-cell Lymphoma

The term “Primary Cutaneous B-Cell Lymphoma” (PCBCL) comprehends a variety of lymphoproliferative disorders characterized by a clonal proliferation of B-cells primarily involving the skin. The absence of evident extra-cutaneous disease must be confirmed after six-month follow-up in order to exclude a nodal non-Hodgkin's lymphoma (NHL) with secondary cutaneous involvement, which may have a completely different clinical behavior and prognosis. In this article, we have summarized the clinico-pathological features of main types of PCBCL and we outline the guidelines for management based on a review of the available literature.

Drug-induced pseudo-Sezary syndrome: a case report and literature review

Pseudo-Sezary syndrome is a benign lymphoproliferative disorder, which clinically and pathologically mimics true Sezary syndrome. In this article, a case of pseudo-Sezary syndrome and review the literature has been reported. The patient was a 51-year-old man who developed erythroderma and palmoplantar keratoderma. The patient's medication history included fosinopril and combination metoprolol/hydrochlorothiazide. Flow cytometry showed a population of 2500 "Sezary-like" CD4726 T cells per microliter in the peripheral blood. Skin biopsy showed numerous atypical lymphocytes with epidermotropism, and there was matching dominant T-cell clonality in the skin and peripheral blood. After stopping all antihypertensive medications, the eruption resolved in its entirety.

Evaluating breast lymphoplasmacytic infiltrates: a multiparameter immunohistochemical study, including assessment of IgG4

Lymphoplasmacytic infiltrates in the breast, a modified skin appendage, include lymphocytic lobulitis, other nonspecific benign proliferations, and mucosa-associated lymphoid tissue (MALT)-type lymphoma. Distinguishing these entities, all of which may be B-cell rich and may have associated sclerosis, can be difficult. In addition, the proportion that represents IgG4-related disease is unknown, and the similarity of MALT lymphomas to primary cutaneous marginal zone lymphoma is uncertain. To address these questions, the clinical, histologic, and immunohistochemical features of 50 benign and malignant breast lymphoplasmacytic infiltrates (10 lymphocytic lobulitis, 1 granulomatous, 19 not otherwise specified, 20 MALT lymphomas) were evaluated. Compared with the MALT lymphomas, benign cases had a less dense infiltrate (P < .001), fewer but more histologically apparent germinal centers (P < .001), and more marked fibrosis (P < .0001). Greater than 60% B cells were present in 23% (7/30) benign cases versus 75% (15/20) MALT lymphomas (P = .0003). Plasma cells were predominantly IgG+ in 83% (24/29) benign cases and predominantly IgM+ in 73% (14/19) MALT lymphomas (P < .0001). None of the benign cases had greater than 50 IgG4+ plasma cells/high-power field, and only 1 lymphocytic lobulitis case had an IgG4/IgG ratio exceeding 40% and no clinical evidence for extramammary IgG4-related disease. Although there may be some overlapping features, routine histopathology together with limited immunohistochemical stains can distinguish benign from neoplastic lymphoplasmacytic infiltrates in the breast. Despite frequent sclerosis, the breast is not a common site of unrecognized IgG4-related sclerosing disease. Although there are similarities, breast MALT lymphomas can be separated from cutaneous marginal zone lymphoma.

Association between lymphocyte antigen receptor gene rearrangements and histopathological evaluation in canine chronic enteropathy

Although definitive diagnosis of chronic enteropathy (CE) and gastrointestinal (GI) lymphoma requires histopathological evaluation of the GI tract, these conditions are often still difficult to differentiate from each other. Polymerase chain reaction (PCR) for antigen receptor gene rearrangements (PARR) has been applied recently as an adjunctive for diagnosis of lymphoid tumors; however, its clinical value in canine CE and GI lymphoma remains unclear. The purpose of this study was to investigate the relationship between PARR and histopathological diagnosis, degree of enteritis or lymphoma, and long-term prognosis in dogs, in order to evaluate the clinical significance of PARR. Endoscopic biopsy specimens obtained from 96 dogs with chronic enteritis (mild, n=14; moderate, n=20; marked, n=62) and 21 dogs with GI lymphoma were used. Clonality was observed in 51% of the animals with chronic enteritis; interestingly, it was found in 29% of those with only mild enteritis. In dogs with marked enteritis, the rate of PARR was higher in those with lymphocyte epitheliotropism than in those without epitheliotropism. The sensitivity of PARR in animals with GI lymphoma was 76%. There was no significant prognostic difference between chronic enteritis with or without clonal rearrangements. In contrast, dogs histopathologically diagnosed with marked enteritis had a significantly shorter survival time than did those with mild or moderate enteritis. While the significance of PARR in the diagnosis of GI lymphoma remains uncertain, the pathological roles of clonally expanding lymphocytes in canine CE should be investigated further.

Detection of immunoglobulin light-chain restriction in cutaneous B-cell lymphomas by ultrasensitive bright-field mRNA in situ hybridization

BACKGROUND

Detection of immunoglobulin light-chain restriction is important in the diagnosis of B-cell non-Hodgkin lymphoma (B-NHL). Flow-cytometry, commonly used to evaluate light-chain restriction, is impractical to be used in cutaneous specimens. Immunohistochemical and conventional chromogenic in situ hybridization (CISH) methods on formalin-fixed-paraffin-embedded (FFPE) tissue lack sufficient sensitivity to detect low-level light-chain expression in B-NHL without plasmacytic differentiation. Ultrasensitive bright-field mRNA-ISH (BRISH) for in situ light-chain detection in cutaneous B-NHL has been assessed.

DESIGN

Kappa/lambda mRNA was detected using two-color BRISH (RNAscope 2xPlex, Advanced Cell Diagnostics) on 27 FFPE skin biopsies and excisions from patients with available B-cell PCR clonality studies: 16 clonal B-cell lesions (6 follicle center lymphoma, 5 marginal zone lymphoma, 3 large B-cell lymphoma, and 2 other) and 11 non-clonal B-cell proliferations.

RESULTS

BRISH was successful in 15/16 clonal B-cell lesions and 11/11 non-clonal proliferations. Light-chain restriction was detected in 15/15 clonal lesions and in 1/11 non-clonal proliferations (96.1% overall concordance with clonality PCR). In 4/5 marginal zone lymphomas, light-chain restriction was detected as strong monotypic mRNA expression in a B-cell subset, consistent with plasmacytic differentiation.

CONCLUSION

Ultrasensitive BRISH can successfully detect light-chain restriction in B-NHL from FFPE skin specimens and may be a useful adjunct ancillary tool in cases not resolved by CISH or immunohistochemical methods.

Cutaneous lymphomas: an update. Part 2: B-cell lymphomas and related conditions

: Primary cutaneous B-cell lymphomas (PCBCL) are the second most common form of primary cutaneous lymphomas and account for approximately 25%-30% of all primary cutaneous lymphomas. Both forms of low-grade malignant PCBCL, primary cutaneous follicle center lymphoma (PCFCL) and primary cutaneous marginal zone lymphoma of mucosa-associated lymphoid tissue-type (MALT lymphoma) (PCMZL) represent the vast majority of PCBCL and show an indolent slowly progressive course and an excellent prognosis despite a high recurrence rate. Genetic analysis indicates that PCMZL differ from other forms of extranodal MALT lymphomas. The more common class-switched and the non-class-switched form of PCMZL can be distinguished as two distinctive subsets that differ in the cellular composition, IgM expression, and biological behavior with extracutaneous involvement found in the non-class-switched form. Recently, unusual clinical and histological forms of PCMZL and PCFCL manifesting with miliary or agminated lesions have been described that are diagnostically challenging. In contrast to PCMZL and PCFCL, primary cutaneous diffuse large B-cell lymphoma, leg type, and other rare forms of large B-cell lymphomas such as intravascular large B-cell lymphoma have an unfavorable prognosis. There is an emerging group of Epstein-Barr virus (EBV)-driven B-cell lymphoproliferations including posttransplant lymphoproliferative disorders and mucocutaneous ulcer occurring in immunocompromised patients and EBV-associated diffuse large B-cell lymphoma of the elderly arising in the setting of senescence-linked immunodeficiency. This review reports on recent findings expanding the spectrum of clinicopathological features, differential diagnostic aspects, and the pathogenesis of PCBCL and discusses the group of EBV-associated B-cell lymphoproliferations involving the skin.

Ultrasensitive RNA in situ hybridization for detection of restricted clonal expression of low-abundance immunoglobulin light chain mRNA in B-cell lymphoproliferative disorders

OBJECTIVES

To assess the feasibility of using a novel ultrasensitive bright-field in situ hybridization approach (BRISH) to evaluate κ and λ immunoglobulin messenger RNA (mRNA) expression in situ in B-cell non-Hodgkin lymphoma (NHL).

METHODS

A series of 110 semiconsecutive clinical cases evaluated for lymphoma with historic flow cytometric (FCM) results were assessed with BRISH.

RESULTS

BRISH light chain restriction (LCR) results were concordant with FCM in 108 (99%) of 109 evaluable cases. Additional small B-cell lymphoma cohorts were successfully evaluated.

CONCLUSIONS

BRISH analysis of κ and λ immunoglobulin mRNA expression is a sensitive tool for establishing LCR in B-cell NHL when FCM results are not available.

Clonality testing of malignant lymphomas with the BIOMED-2 primers in a large cohort of 1969 primary and consultant biopsies

The introduction of the BIOMED-2 primers allowed for reliable comparisons of clonality testing data of malignant lymphomas from different laboratories. This study undertook a retrospective analysis of a large cohort of cases; 1862 cases involved the immunoglobulin heavy chain locus (IGH VH-JH), and 1527 cases involved the T cell receptor gamma locus (TCRG). We confirmed previously published clonality rates in various B cell, T cell, and Hodgkin lymphoma cases. In reactive lesions, clonality for the IGH locus was frequently accompanied by additional polyclonal background. Clonality for TCRG was found in a subgroup of diffuse large B cell lymphomas. On closer morphologic inspection, seven cases appeared to have arisen from an underlying peripheral T-cell lymphoma. Five cases with monoclonal TCRG rearrangements, originally diagnosed as Hodgkin lymphomas, were reclassified as T-cell lymphomas. TCRG clonality was very rarely only observed in Hodgkin lymphoma. In case of clear TCRG clonality a T-cell neoplasia must be ruled out on morphological grounds. By careful examination of the rearrangement patterns, including an assessment of a co-amplified polyclonal background, clonality testing provides a powerful tool which in concert with morphologic and immunohistochemical parameters can lead to a firm diagnosis.

Origin Use of CD4, CD8, and CD1a Immunostains in Distinguishing Mycosis Fungoides from its Inflammatory Mimics: A Pilot Study

Patch-stage/early mycosis fungoides (MF) is difficult to differentiate from benign dermatoses, despite several robust histologic criteria. Most studies include advanced lesions and data about early disease is limited.

Objectives:

(1) To compare the CD4:CD8 ratio in patch-stage MF versus inflammatory mimics. (2) To study patterns of CD1a expression in the epidermis and dermis in the two groups.

Materials and Methods:

Twenty cases each of early MF and inflammatory dermatoses were selected. The diagnoses were established after clinicopathologic correlation, repeat biopsies, and follow-up. The inflammatory group included pityriasis lichenoides chronica, actinic reticuloid, lichenoid purpura, and various psoriasiform dermatoses. Immunohistochemistry was done for CD4, CD8, and CD1a. Epidermal CD4, CD8 cells were quantified and CD1a was graded semi-quantitatively in the epidermis and dermis.

Results:

The average CD4:CD8 ratio was 4.2 in MF (range: 1-16.8), and 0.9 in inflammatory diseases (range: 0.43-5), which was statistically significant (P < 0.0001). None of the MF cases had a ratio <1. Four cases of pityriasis lichenoides chronica had a ratio >1. CD1a cells had a continuous or confluent epidermal pattern in almost all cases of MF, while they occurred as small or large groups in the dermis. In inflammatory dermatoses, there were either isolated or scattered CD1a+ cells in both epidermis and dermis.

Conclusions:

Elevated CD4:CD8 ratio favors MF. But there is an overlap in the lower range with pityriasis lichenoides chronica. These cases require good clinicopathologic correlation and follow-up. Patterns of CD1a expression are more reliable. Immunostains buttress morphology and are a valuable addition.

A case of Borrelia-associated cutaneous pseudolymphoma in a horse

This case report describes a 10-year-old horse that developed multiple dermal papules over the right masseter area following removal of a tick from the same site 3 months earlier. Histological examination of a biopsy from a papule was suggestive of either a T-cell-rich B-cell lymphoma or cutaneous lymphoid hyperplasia, a form of pseudolymphoma sometimes associated with a tick bite. Positive serological testing and PCR of the biopsy sample for Borrelia in conjunction with immunohistochemical testing of the skin biopsy, the clinical history and response to treatment with doxycycline strongly supported the diagnosis of Borrelia-associated cutaneous pseudolymphoma.

A simple and efficient method for DNA extraction from skin and paraffin-embedded tissues applicable to T-cell clonality assays

PCR-based clonality assay of rearranged T-cell receptor genes gamma and beta (TCRG and TCRB) in a number of cases could be essential to discriminate between cutaneous T-cell lymphomas and reactive lymphoproliferative lesions in the skin. However, extraction of good-quality DNA from skin specimens (especially formalin-fixed paraffin-embedded) remains a challenge. Common procedures, being labour-intensive and time-consuming and requiring toxic solvents such as phenol and chloroform, still may end up with DNA sample of insufficient quality. We herewith present a simple and efficient method for DNA isolation based on ammonia extraction of tissue, followed by neutralization and simultaneous salting out of proteins with acetic acid. We have analysed 30 samples - 24 fresh (16 skin, two spleen and six lymph node) and six paraffin-embedded. Standard procedure (proteinase K digestion, followed by phenol/chloroform extraction) has been carried out simultaneously. We observed good PCR signal for TCRG rearrangements in 30 samples processed with the new protocol and only in 20 extracted with proteinase K/phenol/chloroform. For TCRB, the success rate was 29 of 30 with the new protocol, compared to 11 of 30 with conventional protocol. The proposed method of DNA extraction should improve the value of T-cell clonality assay, because insufficient DNA quality and quantity may bias analysis towards monoclonality and therefore cause false-positive results.

Comparison of BIOMED-2 versus laboratory-developed polymerase chain reaction assays for detecting T-cell receptor-gamma gene rearrangements

Detecting clonal T-cell receptor (TCR)-gamma gene rearrangements (GRs) is an important adjunct test for diagnosing T-cell lymphoma. We compared a recently described assay (BIOMED-2 protocol), which targets multiple variable (V) gene segments in two polymerase chain reaction (PCR) reactions (multi-V), with a frequently referenced assay that targets a single V gene segment in four separate PCR reactions (mono-V). A total of 144 consecutive clinical DNA samples were prospectively tested for T-cell clonality by PCR using laboratory-developed mono-V and commercial multi-V primer sets for TCR-gamma GR. The combination of TCR-beta, mono-V TCR-gamma and multi-V TCR-gamma detected more clonal cases (68/144, 47%) than any individual PCR assay. We detected clonal TCR-beta GR in 47/68 (69%) cases. Using either mono-V or multi-V TCR-gamma primers, the sensitivities for detecting clonality were 52/68 (76%) or 51/68 (75%). Using both mono-V and multi-V TCR-gamma primers improved the sensitivity for detecting clonality, 60/68 (88%). Combining either mono-V or multi-V TCR-gamma primers with TCR-beta primers also improved the sensitivity, 64/68 (94%). Significantly, TCR-gamma V11 GRs could only be detected using the mono-V-PCR primers. We conclude that using more than one T-cell PCR assay can enhance the overall sensitivity for detecting T-cell clonality.

[What's new in clinical dermatology]

This selection reviews several topics in the news: - in internal medicine, the cardiovascular and pulmonary risk factors in progressive systemic sclerosis (circulating lupus anticoagulant, smoking, NT-pro BNP marker); the relations between lupus erythematous and polymorphic light eruption, or Jessner-Kanof syndrome; the diagnostic score of autoinflammatory syndromes; and the dysmetabolism syndrome of psoriasis; - in infectious diseases, the return of epidemic typhus; the emergence of TIBOLA rickettsiosis; the development of methicillin-resistant Staphylococcus aureus strains in both the nosocomial and community settings; and finally news on herpes group viral infections.