Histologic mimickers of mycosis fungoides: a review

Preliminary assessment of the accuracy of cutaneous T-cell lymphoma diagnosis through deep sequencing of the TRG gene

BACKGROUND

The diagnostic challenges in early mycosis fungoides (MF) and other cutaneous T-cell lymphomas (CTCLs) persist despite advancements in molecular methods.

OBJECTIVES

To provide a preliminary assessment of next-generation sequencing (NGS) in analysing TRG (T-cell receptor gamma locus) sequences for distinguishing CTCLs from benign inflammatory skin disorders.

METHODS

NGS was used to assess TRG sequences in skin samples from clinicopathologically proven CTCLs and benign inflammatory skin disorders.

RESULTS

Our study analysed skin samples from a total of 36 participants, comprising 22 cases of CTCL, including 14 MF and 8 other CTCLs, alongside 14 cases of benign inflammatory skin disorders. According to LymphoTrack® criteria, monoclonality was detected in 16 (73%) of the 22 patients with CTCL. Specifically, in cases of MF, 10 of 14 (71%) were identified as monoclonal, with all 4 non-monoclonal cases being in the patch stage. For the other cases of CTCL, six of eight displayed monoclonality. Among the 22 patients with CTCL, 10 (45%) had multiple biopsies, with 8 (36%) displaying the same dominant clone across different sites. Among the 14 benign cases, only the case of erythrodermic psoriasis exhibited monoclonality. Our decision tree analysis suggests that a high frequency of the most abundant clone, its ratio to the third most abundant clone and TRG VγI segment usage are effective markers that can help in the diagnosis of CTCL.

CONCLUSIONS

A combination of the clone frequencies and TRG V segment usage may enhance diagnosis of MF and other CTCLs, helping to differentiate them from benign conditions. However, molecular diagnosis for patch-stage MF remains challenging.

Single-cell sequencing delineates T-cell clonality and pathogenesis of the parapsoriasis disease group

BACKGROUND

Mycosis fungoides (MF), the most common cutaneous T-cell lymphoma, is often underdiagnosed in early stages because of similarities with benign dermatoses such as atopic dermatitis (AD). Furthermore, the delineation from what is called "parapsoriasis en plaque", a disease that can appear either in a small- or large-plaque form, is still controversial.

OBJECTIVE

We sought to characterize the parapsoriasis disease spectrum.

METHODS

We performed single-cell RNA sequencing of skin biopsies from patients within the parapsoriasis-to-early-stage MF spectrum, stratified for small and large plaques, and compared them to AD, psoriasis, and healthy control skin.

RESULTS

Six of 8 large-plaque lesions harbored either an expanded alpha/beta or gamma/delta T-cell clone with downregulation of CD7 expression, consistent with a diagnosis of early-stage MF. In contrast, 6 of 7 small-plaque lesions were polyclonal in nature, thereby lacking a lymphomatous phenotype, and also revealed a less inflammatory microenvironment than early-stage MF or AD. Of note, polyclonal small- and large-plaque lesions characteristically harbored a population of NPY+ innate lymphoid cells and displayed a stromal signature of complement upregulation and antimicrobial hyperresponsiveness in fibroblasts and sweat gland cells, respectively. These conditions were clearly distinct from AD or psoriasis, which uniquely harbored CD3+CRTH2+ IL-13 expressing "TH2A" cells, or strong type 17 inflammation, respectively.

CONCLUSION

These data position polyclonal small- and large-plaque parapsoriasis lesions as a separate disease entity that characteristically harbors a so far undescribed innate lymphoid cell population. We thus propose a new term, "polyclonal parapsoriasis en plaque", for this kind of lesion because they can be clearly differentiated from early- and advanced-stage MF, psoriasis, and AD on several cellular and molecular levels.

Mycosis fungoides and Sézary syndrome - Simplifying the approach for dermatologists. Part 1: Etiopathogenesis, clinical features and evaluation

Cutaneous T-cell lymphomas (CTCL) are a heterogeneous group of extranodal non-Hodgkin's lymphomas characterised by a cutaneous infiltration of malignant monoclonal T lymphocytes. While this broad spectrum of disease with its varied etiopathogenesis, clinical features and management options are well characterised, an approach from a dermatologist's perspective is lacking in the literature. We strive to elucidate the approach from a clinician's point of view, especially in respect of clinical examination, investigations, staging and management options that are available in the realm of the dermatologists. This review article is the first part out of the two, covering the etiopathogenesis, clinical features and evaluation.

Cell adhesion molecule 1 expression in mycosis fungoides versus parapsoriasis versus inflammatory dermatosis: an immunohistochemical comparative study

Cell adhesion molecule 1 (CADM1) is one of the immunoglobulin super family adhesion molecules, that is proposed to contribute in the pathogenesis of various types of cutaneous T-cell lymphoma, including mycosis fungoides (MF). In this work, we decided to examine the immunohistochemical expression of CADM1 in MF specimens compared to premycotic parapsoriasis, benign inflammatory dermatosis and normal control skin specimens. 125 participants were enrolled (50 MF, 25 parapsoriasis, 25 inflammatory dermatosis, and 25 healthy controls). Patients were selected from the Outpatient Clinic of Dermatology and Venereology Department, Tanta University Hospitals. From all, 4 mm punch skin biopsies were taken and examined for CADM1 immunohistochemical expression. The current study revealed statistically significant upregulation of CADM1 expression in MF specimens in comparison to parapsoriasis, inflammatory dermatosis, and normal control specimens. Additionally, there was statistically significant positive correlation between CADM1 expression and progression of TNMB staging of MF disease. Therefore, it is possible to recommend CADM1 as a beneficial diagnostic immunohistochemical marker for differentiation between early stages of MF and both the premycotic parapsoriasis and benign inflammatory dermatosis. Moreover, it may be of value in early detection of neoplastic transformation of parapsoriasis as well as in assessment of MF progression.

Interface change in early mycosis fungoides: A potential mimicker of benign dermatoses

BACKGROUND

Histopathologic features of interface dermatitis can occasionally be seen in mycosis fungoides (MF), particularly in early patch-stage disease.

MATERIALS AND METHODS

We identified six patients with MF whose early biopsy specimens showed such prominent interface dermatitis that a benign diagnosis was favored. All subsequent specimens were reviewed for these patients, and the histopathologic evolution of disease was documented. Immunohistochemistry (IHC) for CD2, CD3, CD4, CD5, CD7, CD8, CD30, and CD123 was performed retrospectively. Educational archives were reviewed to assess the incidence of interface dermatitis in biopsies otherwise diagnostic of MF.

RESULTS

A spectrum of vacuolar and lichenoid patterns of interface change was observed in this series of six patients eventually diagnosed as having MF, and was seen as a recurring pattern in multiple specimens over time. In retrospect, findings described in early MF such as lining up of lymphocytes along the dermal-epidermal junction within the basal layer, papillary dermal fibrosis, and intraepidermal lymphocyte atypia could be appreciated to varying degrees in the confounding specimens. CD123 was negative in all cases, putatively excluding a connective tissue disease (CTD). None of the early biopsies showed loss of pan-T antigens CD2, CD5, and CD7. Forty-six of 164 cases (28%) of MF in an archival study set showed varying degrees of interface dermatitis in the setting of otherwise diagnostic changes of MF.

CONCLUSIONS

Early MF can show prominent interface change and mimic inflammatory dermatoses. Histopathologic clues suggestive of MF should be carefully assessed, and IHC for CD123 may be helpful in distinguishing MF from CTD. Repeat biopsies over time may be necessary to arrive at a definitive diagnosis, in conjunction with ancillary studies and strong clinicopathologic correlation.

The Value of Immunohistochemical Expression of TOX, ICOS, and GATA-3 in the Diagnosis of Mycosis Fungoides

BACKGROUND

Mycosis fungoides (MF) is considered the commonest type of cutaneous T-cell lymphoma representing about 50% of all primary cutaneous lymphomas. Differentiation between MF and another inflammatory dermatitis (BIDs) is important to ensure proper management.

AIM

We aimed to evaluate the immunohistochemical expression of T OX, ICOS, and GATA binding protein 3 (GATA-3) in early stages MF (stage IA and IB) to establish their diagnostic value and to guide the use of inhibitors in the treatment of cutaneous T-cell lymphomas.

MATERIALS AND METHODS

A retrospective study of 75 skin paraffin blocks (punch biopsy) 40 cases of MF and 35 cases of eczematous dermatitis as a group representing other inflammatory dermatitis were retrieved from archives of the pathology department of our University, during the period from October 2017 to May 2021.

RESULTS

About 98% and 90% of patients in the MF group had positive T OX and ICOS, while 70% of them had positive GATA-3. High expression of T OX, ICOS, and GATA-3 was associated with higher stages.

CONCLUSIONS

T OX is considered a diagnostic marker for early MF. The importance of identifying novel markers in MF expressed by immunohistochemistry, such as ICOS, has been established. According to our results, GATA-3 could be used as an accessory marker in the diagnosis of MF when combined with T OX and ICOS in a panel.

Updates and Proposed Diagnostic Approach to Psoriasiform Dermatoses

Psoriasiform dermatoses represent a wide array of skin diseases commonly encountered by clinicians and pathologists. While they may present a diagnostic challenge, thorough observation coupled with proper interpretation of subtle additional clinical or histopathologic features provide clues to the correct diagnosis. In this review, we provide updates on emerging entities and develop a systemic approach to establish the pathologic diagnosis, with emphasis on the importance of clinicopathologic correlation.

Mass Cytometric Analysis of Early-Stage Mycosis Fungoides

Mycosis fungoides (MF) is the most common subtype of cutaneous T-cell lymphoma. Early-stage disease is characterized by superficial infiltrates of small- to medium-sized atypical epidermotropic T lymphocytes that are clonal related. Nevertheless, the percentage of atypical T cells is low with many admixed reactive immune cells. Despite earlier studies, the composition and spatial characteristics of the cutaneous lymphocytic infiltrate has been incompletely characterized. Here, we applied mass cytometry to profile the immune system in skin biopsies of patients with early-stage MF and in normal skin from healthy individuals. Single-cell suspensions were prepared and labeled with a 43-antibody panel, and data were acquired on a Helios mass cytometer. Unbiased hierarchical clustering of the data identified the major immune lineages and heterogeneity therein. This revealed patient-unique cell clusters in both the CD4⁺ and myeloid cell compartments but also phenotypically distinct cell clusters that were shared by most patients. To characterize the immune compartment in the tissue context, we developed a 36-antibody panel and performed imaging mass cytometry on MF skin tissue. This visualized the structure of MF skin and the distribution of CD4⁺ T cells, regulatory T cells, CD8⁺ T cells, malignant T cells, and various myeloid cell subsets. We observed clusters of CD4⁺ T cells and multiple types of dendritic cells (DCs) identified through differential expression of CD11c, CD1a, and CD1c in the dermis. These results indicated substantial heterogeneity in the composition of the local immune infiltrate but suggest a prominent role for clustered CD4-DC interactions in disease pathogenesis. Probably, the local inhibition of such interactions may constitute an efficient treatment modality.

Baby Wet Wipes: An Unusual Culprit of Lymphomatoid Contact Dermatitis Mimicking Mycosis Fungoides

ABSTRACT

Lymphomatoid contact dermatitis (LCD) is a rare, benign pseudolymphoma with clinicopathologic features of both allergic contact dermatitis and cutaneous T-cell lymphoma (CTCL). In this article, we report a fascinating case of LCD secondary to chronic baby wet wipe use with clinical features of allergic contact dermatitis and histopathologic changes of mycosis fungoides, a subtype of CTCL. We argue that LCD should be added to the list of mimickers of mycosis fungoides, a subtype of CTCL.

Cutaneous T-cell lymphoma in erythrodermic cases may be suspected on the basis of scalp examination with dermoscopy

Erythrodermic variants of cutaneous T-cell lymphoma (CTLC) are one of the case of erythroderma. The aim of the study was to assess the value of scalp dermoscopy in differentiation between erythrodermic CTCL, psoriasis, and atopic dermatitis. A total of 76 patients were included into the study (16 patients with erythrodermic CTCL, 20 patients with psoriatic erythroderma, 20 with erythrodermic atopic dermatitis, and 20 healthy volunteers). The most common trichoscopic features of erythrodermic CTCL were: numerous pili torti, numerous broken hairs, white thick interfollicular bands, and patchy hyperpigmentation of the background. They were observed in 81% (13/16), 75% (12/16), 56% (9/16), and 37.5% (6/16) of patients with CTCL, respectively (p < 0.001). Other specific features of erythrodermic CTCL were 8-shaped hairs (19%; 3/16) and visible anagen bulbs (12.5%; 2/16) (p < 0.05 and p = 0.052, respectively). The most common vascular pattern of erythrodermic CTCL was perifollicular arrangement of glomerular (50%; 8/16; p < 0.001) or linear vessels (31%; 5/16; p < 0.05). Follicular spicules-like scaling was pathognomonic for erythrodermic CTCL (12%, 2/16) although its presence did not reach statistical significance (p = 0.052). In conclusion, the characteristic trichoscopic findings of erythrodermic CTCL are numerous pili torti, eight-shaped hairs, thick white interfollicular bands, color heterogeneity of the background and perifollicular arrangement of vessels.

Is it mycosis fungoides? A comprehensive guide to reaching the diagnosis and avoiding common pitfalls

Mycosis Fungoides (MF) is known as 'the great mimicker' due to its capacity to emulate several dermatoses, both in the clinic and on histology. This often leads to the diagnosis being missed or delayed, which consequently leads to poorer prognosis. For a timely diagnosis, it is crucial that the physician is aware of the various clinical and histological presentations of MF, as well as the proper diagnostic protocols. In the current review, we concisely encapsulate all the variants of MF as well has the conditions it mimics clinically and histologically. Through this, we aim to provide clinicians with a holistic picture of MF and help them determine when to suspect this disease and steps to take in order to nail the diagnosis.

A case of cutaneous extranodal natural killer/T-cell lymphoma clinically and histopathologically mimicking interface dermatitis

Extranodal natural killer/T-cell lymphoma (ENKTL) is a rare but aggressive cancer characterised by angiocentric and angiodestructive infiltration by NK-cells, or cytotoxic T-cell types. Histopathologically, ENKTL shows a multinodular or diffuse infiltration localised to vascular structures, resulting in angiodestruction and necrosis. We present a patient with an initially suspected diagnosis of benign interface dermatitis with a differential diagnosis of mycosis fungoides that was later found to be an aggressive extranodal natural killer/T-cell lymphoma of a nasal type and with a dismal prognosis.

Histopathologic features distinguishing secondary syphilis from its mimickers

BACKGROUND

Syphilis is often misdiagnosed clinically, and biopsies might be required.

OBJECTIVE

To determine histopathologic features that distinguish secondary syphilis from pityriasis lichenoides (PL), pityriasis rosea (PR), and early mycosis fungoides (MF).

METHODS

Histopathologic features of 100 cases of syphilis, 110 cases of PL, 72 cases of PR, and 101 cases of MF were compared.

RESULTS

Elongated rete ridges and interstitial inflammation favor syphilis over PL (likelihood ratios 3.44 and 2.72, respectively), but no feature reliably distinguishes between them. Secondary syphilis and PR can be distinguished by neutrophils in the stratum corneum, plasma cells, interface dermatitis with lymphocytes and vacuoles, and lymphocytes with ample cytoplasm. Plasma cells and lymphocytes with ample cytoplasm are rare in early MF and can be used as distinguishing features.

CONCLUSIONS

Histopathologic features characteristic of syphilis can be seen in PL, PR, and early MF. Distinguishing syphilis from PL can be difficult histologically, and a high index of suspicion is required. Although elongation of rete and interstitial inflammation favor syphilis, plasma cells (historically considered a significant feature of syphilis) are often encountered in PL. Vacuolar interface dermatitis with a lymphocyte in every vacuole is considered characteristic of PL, but this feature appears to be more common in syphilis.

Hodgkin's lymphoma in a patient on adalimumab treatment for psoriasis

Adalimumab is a human monoclonal antibody which targets tumor necrosis factor (TNF)-alpha. It is produced by recombinant DNA technology, using a mammalian cell expression system and is widely-known to treat a number of immune-mediated conditions, including psoriasis. There has been a growing concern regarding the possible association between TNF-alpha inhibitors and malignancy. In this case report, we describe the case of a 20-year-old woman, known to have been suffering from chronic plaque psoriasis for 12 years, and who developed Hodgkin's lymphoma within five weeks of beginning adalimumab treatment.

An uncommon diagnosis for a recurrent erythematous patch in a paediatric patient

A 14-year-old girl presented with a circular erythematous patch over the left buttock for approximately 10 years, with ongoing ulceration and papules developing over the last 4 years. Punch biopsies were taken within and above the patch for diagnosis. Both revealed marked inflammatory infiltrates with atypical, irregular lymphocytes and increased mitosis. Immunostaining revealed CD8 positivity and a pan T helper cell phenotype. T cell receptor gene rearrangement analysis showed T cell clonality in both biopsies. These findings were consistent with mycosisfungoides and associated lymphomatoid papulosis. Both are rare conditions but have been associated in 5%-20% of cases. A definitive association has not yet been established; however, T cell monoclonality shows 50%-60% share a common origin. Management options are extensive with no one treatment showing superiority. Our patient received low-dose radiotherapy with good outcomes, but subsequently required further radiotherapy.

Lichenoid Dermatitis of the Vulva: Diagnosis and Differential Diagnosis for the Gynecologic Pathologist

Inflammatory processes affecting the vulva may present a unique challenge due to location specific changes. Different factors are behind the intricacy in the presentation of vulvar dermatoses. First, the vulva is lined by different epithelia (hair-bearing keratinized epithelium, modified mucosa, and mucosa). Furthermore, among other factors, this organ is exposed to friction, occlusion, and trauma. Lastly, as there is a tendency to look for health care advice at an advanced stage of the disease, the lesion may be modified by secondary changes due to self-treatment. This article describes the clinical presentation and pathologic features of vulvar dermatoses with a lichenoid pattern and highlights practical points for their diagnoses.

Fulminant Mycosis Fungoides with Tissue Eosinophilia: A Unique Presentation of Two Cases with Acro-Periorbital Ulceration and An Aggressive Clinical Course

We describe two unique cases of fulminant mycosis fungoides with remarkably similar and aggressive clinical courses resulting in death. Both cases demonstrated ulcerated palmar and periorbital plaques and marked tissue eosinophilia, which was confirmed by T-cell receptor γ chain gene rearrangement studies to display identical monoclonality at temporally and anatomically distinct sites. Dense eosinophilic infiltrates on biopsy led to misdiagnosis of inflammatory dermatoses in both instances.

While mycosis fungoides may be challenging to diagnose histologically, the presence of eosinophils in progressive disease may herald a poor prognosis and should not exclude the diagnosis.

Defining the mimics and clinico-histological diagnosis criteria for mycosis fungoides to minimize misdiagnosis

Background

Mycosis fungoides (MF) is a significant diagnostic challenge; it has various differential diagnosis especially at an early stage. Our aim was to describe mimics of MF clinically and histologically, and to define significant diagnostic criteria of the disease.

Methods

This was a retro-prospective cohort of 370 patients in whom the diagnosis of MF was suspected clinically.

Results

MF was histologically confirmed in 15.4% of cases and rejected in 84.5%. Other identified histologically diagnosis were eczema, psoriasis; nonspecific dermatitis, lichen, lupus; pseudolymphoma, parapsoriasis and toxidermia. 4 patients with palmoplantar MF were wrongly treated as eczema, and 10 patients with psoriasiform MF were initially treated as psoriasis. We also described the clinical, histological and immunohistochemistry diagnostic criteria for distinguishing MF from benign dermatosis.

Conclusions

Misdiagnosis of MF was a real problem for this study, because it shared common clinical and histological characteristics with other inflammatory diseases like eczema and psoriasis. Therefore, defining significant clinico-histological diagnosis criteria of MF would be of great help and would increase the accuracy of the diagnosis.

Selected Inflammatory Imitators of Mycosis Fungoides: Histologic Features and Utility of Ancillary Studies

Mycosis fungoides is the most common primary cutaneous lymphoma; however, it remains a significant diagnostic challenge, in part because of the overlap with several inflammatory dermatoses. Despite advances in immunohistochemistry and molecular diagnostics, false-positive, false-negative, and indeterminate diagnoses are not uncommon. In most cases, the overall balance of morphologic, immunophenotypic, and genetic features must be considered carefully because there are few sensitive and specific clues to the diagnosis. Moreover, an appropriate clinical presentation is essential to the diagnosis and helps to favor or exclude inflammatory/reactive processes. Herein, we discuss 3 important inflammatory dermatoses that may closely simulate mycosis fungoides, and we review the use of ancillary studies in these challenging cases.

Mimics of cutaneous lymphoma: report of the 2011 Society for Hematopathology/European Association for Haematopathology workshop

The Society for Hematopathology and European Association for Haematopathology workshop, from October 27 to 29, 2011, in Los Angeles, CA, exhibited many exemplary skin biopsy specimens with interesting inflammatory changes mimicking features of cutaneous lymphoma. This article reviews features observed in cutaneous lymphoid hyperplasia, cutaneous drug reactions, lupus-associated panniculitis, pityriasis lichenoides, hypereosinophilic syndrome, histiocytic necrotizing lymphadenitis, traumatic ulcerative granuloma with stromal eosinophils, and pigmented purpuric dermatosis, as well as a brief review of the pertinent literature and discussion of submitted conference cases. For the pathologist, it is important to be aware of diagnostic pitfalls as well as the limitations of ancillary testing (eg, clonality studies). Finally, correlation with total clinical information, good communication with clinical colleagues, close clinical follow-up with rebiopsy, and prudent use of laboratory studies are vital and will likely offer the best path toward a correct diagnosis.

Mycosis fungoides and Sézary syndrome: clinical, histopathological and immunohistochemical review and update

This paper reviews the diagnostic and classificatory concepts of mycosis fungoides and Sézary syndrome in light of the latest normative publications. It describes the great variability of the clinical expression of mycosis fungoides in its early stages as well as the histopathological and immunohistochemical aspects that help with diagnosis. The diagnostic criteria required for characterizing Sézary syndrome and the staging system used for both mycosis fungoides and Sézary syndrome are described.

Current knowledge in inflammatory dermatopathology

The complex and fascinating spectrum of inflammatory skin disease, and the comprehension of it, is ever expanding and evolving. During the first decade of the 21st century, numerous advances in the understanding of inflammatory disease mechanisms have occurred, particularly in psoriasis and atopic dermatitis. Continuation of this trend will assure a future in which molecular tests for biomarkers of immediate clinical relevance are used in routine patient care, not only for diagnosis but also for prognosis and management. This article focuses on selected recent or noteworthy developments that are clinically relevant for the histologic diagnosis of inflammatory skin diseases.

Dermoscopy of early stage mycosis fungoides

BACKGROUND

Early stage mycosis fungoides (MF) is difficult to be clinically differentiated from chronic dermatitis (CD) in a high proportion of patients. Dermoscopy is a rapid, cheep, non-invasive and widely used method for the evaluation of skin tumours and, recently, of inflammatory skin diseases, as well.

OBJECTIVE

To describe the dermoscopic pattern of early stage MF and compare it with the dermoscopic features observed in CD.

METHODS

This was a retrospective study. Dermoscopic images of lesions that were clinically equivocal between MF and CD were evaluated for the presence of predefined morphologic criteria. Diagnosis had been histopathologically and immunohistochemically confirmed in all cases. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated for predefined dermoscopic criteria in relation to the diagnosis of mycosis fungoides.

RESULTS

A total of 67 dermoscopic images were selected for dermoscopic evaluation. Mycosis fungoides lesions exhibited a characteristic dermoscopic pattern consisting of fine short linear vessels (sensitivity 93.7%, specificity 97.1%) and orange-yellowish patchy areas (sensitivity 90.6%, specificity 99.7%). A characteristic vascular structure resembling spermatozoa was also found to be highly specific for the diagnosis of mycosis fungoides. CD was typified by a different dermoscopic pattern, usually consisting of dotted vessels.

CONCLUSIONS

These observations provide a first indication that early stage MF exhibits a characteristic dermoscopic pattern which is different from CD. Prospective studies with long term follow-up are needed to determine the value of these dermoscopic criteria in the differentiation between the two entities in the daily routine.

Hypopigmented mycosis fungoides in type v skin: a report of 5 cases

Five patients with type V skin were studied to describe the clinical manifestations, pathological features, and treatment response in hypopigmented mycosis fungoides (HMF). The mean age of patients was 22.4 years at diagnosis, with a mean of 36 months of diagnostic delay. Two were children aged 11 and 13 years. Skin patches were limited to sunlight-covered body areas. In tropical climate, exposure to natural sunlight possibly cured the lesions on sun-exposed areas at early stage of onset. HMF may frequently be misinterpreted as eczema, vitiligo, or progressive macular hypomelanosis clinically and histopathologically as seen in our case series.

Cutaneous involvement by colonic extranodal NK/T-cell lymphoma mimicking mycosis fungoides: a case report*

We report a 51-year-old woman with cutaneous involvement by extranodal NK/T-cell lymphoma (TCL) of the colon that microscopically mimicked mycosis fungoides (MF). She had a history of fever of unknown origin for 2 months and then developed multiple erythematous papules on her trunk and extremities. A skin biopsy revealed superficial infiltration by atypical small to medium-sized lymphocytes with epidermotropism and Pautrier collections. Immunohistochemical studies showed expression of CD3 and TIA-1 with lack of expression (double negative) of CD4 and CD8. Initially, we reported the diagnosis as MF, cytotoxic variant. Thereafter, computerized tomography scan incidentally identified a colonic mass. A colonic biopsy revealed infiltration of atypical lymphoid cells with the same morphology and immunophenotype as those found in the skin. Additionally, CD56 and Epstein-Barr virus-encoded RNA in situ hybridization in both skin and colonic biopsies were diffusely positive. Thus, extranodal NK/TCL was diagnosed. Delta T-cell receptor (TCR) gene rearrangement was documented in the skin biopsy by polyacrylamide gel electrophoresis and fluorescence capillary gel electrophoresis methods. There was no TCR gene rearrangement detected in the colonic biopsy. Unfortunately, the patient died within 2 months of diagnosis.

Extragenital lichen sclerosus et atrophicus mimicking cutaneous T-cell lymphoma: report of a case

Early lesions of lichen sclerosus et atrophicus (LSA) may present as a mild lichenoid tissue reaction, occasionally together with basilar epidermotropism, mimicking early cutaneous T-cell lymphoma, mycosis fungoides (MF) variant. We report a case of extragenital LSA in which both histological patterns were present in the same clinically homogenous and stable lesion. A 27-year-old man presented with a history of white atrophic plaques on the trunk. A biopsy of an abdominal lesion revealed epidermal thinning, a superficial perivascular lymphoid cell infiltrate with focal epidermotropism, mild nuclear atypia and perinuclear halos. Immunophenotyping showed decreased CD5 and CD7, with a slight predominance of CD8-positive T-lymphocytes. All these changes were suggestive of MF. However, a repeat biopsy 3 months later from the same stable plaque revealed features diagnostic of LSA. LSA mimicking early MF histologically has been reported in genital skin. Conversely, MF may clinically and histopathologically resemble LSA. With gene rearrangement studies, clonal proliferation may not be detected in early MF but has been reported to occur in LSA. Awareness of the histopathologic spectrum of LSA within a stable plaque is important to avoid a potential diagnostic pitfall, and should prompt a repeat biopsy.

Pagetoid reticulosis (Woringer-Kolopp disease)

Pagetoid reticulosis (Woringer-Kolopp disease) is a rare subtype of cutaneous CD8-positive T-cell lymphoma. A 41-year-old man presented with a 7-year history with a slowly progressive erythematous plaque on his right buttocks. With the working diagnosis of psoriasis, he was treated with topical corticosteroids which produced no improvement. Histological examination showed an epidermotropic T-cell lymphoma with predominance of CD8- vs.CD4-positive lymphocytes. Based on the clinical picture and the histological findings, we diagnosed pagetoid reticulosis. Excision of the plaque and cream PUVA photo-chemotherapy produced long-term remission.