F13A1 transglutaminase expression in human adipose tissue increases in acquired excess weight and associates with inflammatory status of adipocytes.

OBJECTIVE: F13A1/FXIII-A transglutaminase has been linked to adipogenesis in cells and to obesity in humans and mice, however, its role and associated molecular pathways in human acquired excess weight have not been explored. METHODS: We examined F13A1 expression and association to human weight gain in weight-discordant monozygotic twins (Heavy-Lean difference (ΔWeight, 16.8 kg ± 7.16 for n = 12). The twin pairs were examined for body composition (by dual-energy X-ray absorptiometry), abdominal body fat distribution (by magnetic resonance imaging), liver fat content (by magnetic resonance spectroscopy), circulating adipocytokines, leptin and adiponectin, as well as serum lipids. Affymetrix full transcriptome mRNA analysis was performed from adipose tissue and adipocyte-enriched fractions from subcutaneous abdominal adipose tissue biopsies. F13A1 differential expression between the heavy and lean co-twins was examined and its correlation transcriptome changes between co-twins were performed. RESULTS: F13A1 mRNA showed significant increase in adipose tissue (p < 0.0001) and an adipocyte-enriched fraction (p = 0.0012) of the heavier co-twin. F13A1 differential expression in adipose tissue (Heavy-Lean ΔF13A1) showed significant negative correlation with circulating adiponectin (p = 0.0195) and a positive correlation with ΔWeight (p = 0.034), ΔBodyFat (0.044) and ΔAdipocyte size (volume, p = 0.012;) in adipocyte-enriched fraction. A whole transcriptome-wide association study (TWAS) on ΔF13A1 vs weight-correlated ΔTranscriptome identified 182 F13A1-associated genes (r > 0.7, p = 0.05) with functions in several biological pathways including cell stress, inflammatory response, activation of cells/leukocytes, angiogenesis and extracellular matrix remodeling. F13A1 did not associate with liver fat accumulation. CONCLUSIONS: F13A1 levels in adipose tissue increase with acquired excess weight and associate with pro-inflammatory, cell stress and tissue remodeling pathways. This supports its role in expansion and inflammation of adipose tissue in obesity.

Evaluation and comparison of staining patterns of factor XIIIa (AC-1A1), adipophilin and GATA3 in sebaceous neoplasia.

BACKGROUND: Reliable nuclear immunohistochemical stains for sebaceous neoplasms have not been readily available. Positive nuclear staining has been reported for GATA3 and factor XIIIa (AC-1A1). We sought to determine the diagnostic utility of these nuclear stains by comparing their staining pattern to adipophilin, a consistently positive cytoplasmic stain. METHODS: Cases with the diagnosis of sebaceous hyperplasia, sebaceous adenoma, sebaceous epithelioma/sebaceoma, sebaceous carcinoma, and nonsebaceous neoplasms (basal cell carcinoma and squamous cell carcinoma) were examined. Intensity and extent of staining of the basal cells and mature sebocytes were evaluated for each stain. RESULTS: Factor XIIIa (AC-1A1) was 87.3% sensitive and 95.1% specific for all sebaceous neoplasms sand showed high inter-observer reliability. Adipophilin was 83.2% sensitive and 87.8% specific. GATA3 was the least sensitive (80.9%) and specific (75.6%) marker. When factor XIIIa was compared against composite staining of all three markers its staining was still uniquely significant (P = .0210). CONCLUSION: Factor XIIIa (AC-1A1) is a sensitive and specific nuclear marker for sebaceous differentiation. Its diagnostic utility exceeds that of adipophilin. Factor XIIIa should be included in the expanding group of immunohistochemical and special stains which can be utilized to aid in the diagnosis of sebaceous neoplasms.

Biphenotypic sinonasal sarcoma: an expanded immunoprofile including consistent nuclear ß-catenin positivity and absence of SOX10 expression.

Biphenotypic sinonasal sarcoma (BSNS) is a recently recognized low-grade sarcoma that exhibits both neural and myogenic differentiation. This unique dual phenotype stems from recurrent rearrangements in PAX3, a transcription factor that promotes commitment along both lineages. While identification of PAX3 rearrangements by fluorescence in situ hybridization (FISH) can confirm a BSNS diagnosis, this assay is not widely available. This study evaluates whether an expanded immunohistochemical panel can facilitate recognition of BSNS without molecular analysis. Eleven cases of BSNS were identified from the surgical pathology archives of two academic medical centers. In 8 cases, the diagnosis was confirmed by FISH using custom probes for PAX3. In 3 cases, FISH failed but histologic and immunophenotypic findings were diagnostic for BSNS. All 11 BSNS (100%) were at least focally positive for S100 as well as calponin and/or smooth muscle actin. In addition, 10 (91%) of 11 expressed nuclear ß-catenin, 8 (80%) of 10 expressed factor XIIIa, 4 (36%) of 11 expressed desmin, and 3 (30%) of 10 expressed myogenin. All 11 tumors were negative for SOX10. While no single marker resolves immunohistochemical overlap between BSNS and its histologic mimickers such as nerve sheath tumors, an extended immunohistochemical panel that includes ß-catenin and SOX10 helps to support the diagnosis of BSNS without the need for gene rearrangement studies.

Histopathologic characteristics of scleromyxedema: A study of a series of 34 cases.

BACKGROUND: Few histologic studies describe the histopathologic aspects of scleromyxedema. OBJECTIVE: We sought to describe the histopathologic and immunohistochemical features of scleromyxedema in a large series of patients. METHODS: We studied all the cases with scleromyxedema diagnosed between 2000 and 2014 at participating centers. Sections with hematoxylin-eosin and special stains were examined. Immunohistochemistry for CD3, CD4, CD8, CD20, CD68, and factor XIIIa was performed in 10 cases. RESULTS: A total of 44 skin biopsy specimens from 34 patients were reviewed. Two different histopathologic patterns were observed: the classic microscopic triad (dermal mucin deposition, fibroblast proliferation, fibrosis) was identified in 34 specimens, whereas an interstitial granuloma annulare-like pattern was found in 10 specimens. A superficial perivascular infiltrate with T lymphocytes was found in all specimens whereas an interstitial proliferation of CD68(+) epithelioid cells was identified in the 10 specimens with an interstitial granuloma annulare-like pattern. Elastic fibers were largely lost, explaining the redundant folds of the disease. LIMITATIONS: This was a retrospective study. CONCLUSIONS: Scleromyxedema shows 2 histopathologic patterns, including the classic type with the microscopic triad of mucin, fibroblast proliferation and fibrosis, and an interstitial granuloma annulare-like pattern. Recognition of these histologic presentations expands the spectrum of scleromyxedema and highlights the difficulty in diagnosing this disabling condition in the absence of a clinicopathological correlation.

[About a case of calcifying fibrous tumor of the pleura]. / À propos d'un cas de tumeur calcifiante de la plèvre.

Calcifying fibrous tumor is a rare soft tissue benign tumor (OMS 2002). Some pleural localisations are described, which affect slightly older individuals than the other soft tissue forms. The calcifying fibrous tumor is included in the 2004 World Health Organization classification of pleural tumors. A pleural tumor located in the right inferior pulmonary lobe is diagnosed in a 59-year-old man. This pleural tumor is macroscopically well-circumscribed. Histologically, the rare spindle tumoral cells are located between bundles of a collagenous tissue, sometimes hyalinized, with psammomatous or dystrophic calcifications. The tumoral cells have a fibrohistiocytic origin. They stain positively for antibodies against vimentin, factor XIIIa, CD68, CD163, CD34. Antibodies against smooth muscle actin, desmin, PS100, ALK1 and EBV are negative. Main differencial diagnoses are other benign pleural tumors (solitary fibrous tumor, inflammatory myofibroblastique tumor), some malignant tumors (desmoplastic malignant pleural mesothelioma) and pleural pseudotumors (calcified pleural plaques, chronic fibrous pleuritis, amylose, hyalinizing granuloma). Our case is the 15th pleural calcifying fibrous tumor being reported.

Dermal dendrocytes FXIIIa+ are essential antigen-presenting cells in indeterminate leprosy.

Indeterminate leprosy (IL) is the early phase of Hansen disease and reword (APCs). Langerhans cells and dermal dendrocytes FXIIIa positive (DDFXIIIa) are the major APCs in the skin and can be identified by the expression of CD1a and FXIIIa, respectively, by immunohistochemical techniques. Plasmacytoid dendritic cells (PDCs) are another type of dermal dendrocytes with a questionable antigen-presenting function and can be highlighted by anti-CD123 expression. To our knowledge, there are no studies evaluating DDFXIIIa and PDC in IL. The purpose was to investigate the involvement of these cells in the pathogenesis of IL. The authors performed a retrospective study on 18 cases of IL (10 confirmed and 8 suspected) to investigate expression of FXIIIa, CD1a, and CD123. The results were compared with normal skin (for CD1a and FXIIIa only). A higher amount of FXIIIa-positive cells (P , 0.05) in confirmed and suspected IL cases was noted when comparing with normal skin. However, CD1a showed no quantitative differences in the epidermis of IL lesions when comparing with normal skin and CD123 expression was negligible. Based on these findings, the authors postulate that Langerhans cells and PDCs do not have a major role in IL and that DDFXIIIa may be the main APCs in IL. Further study is required to establish this.

Tissue immunostaining for factor XIIIa in dermal dendrocytes of pityriasis alba skin lesions.

BACKGROUND: Pityriasis alba affects 1% of the world population and about 9.9% of the children in Brazil. However, its etiology remains uncertain. OBJECTIVE: The objective of the present study was to evaluate the immunoexpression of factor XIIIa in dermal dendrocytes of skin lesions of pityriasis alba. METHOD: Twenty patients with pityriasis alba and 20 patients with atopic dermatitis underwent biopsy. The dermal dendrocytes marked by factor XIIIa were counted by means of immunohistochemical analysis. RESULTS: The mean amount of dermal dendrocytes found in the patients with pityriasis alba was 2, whereas in the patients with atopic dermatitis it was 4, with a statistically significant difference between them. A cutoff point of 3 cells/square inch was established to differentiate pityriasis alba from atopic dermatitis, with 80% sensibility and 90% specificity. CONCLUSION: We believe that pityriasis alba and atopic dermatitis should be considered different clinical forms within the spectrum of atopic disease, in which sun radiation plays an important role by modulating the progression of the disease.

Tissue immunostaining for factor XIIIa in dermal dendrocytes of pityriasis alba skin lesions

BACKGROUND: Pityriasis alba affects 1% of the world population and about 9.9% of the children in Brazil. However, its etiology remains uncertain. OBJECTIVE: The objective of the present study was to evaluate the immunoexpression of factor XIIIa in dermal dendrocytes of skin lesions of pityriasis alba. METHOD: Twenty patients with pityriasis alba and 20 patients with atopic dermatitis underwent biopsy. The dermal dendrocytes marked by factor XIIIa were counted by means of immunohistochemical analysis. RESULTS: The mean amount of dermal dendrocytes found in the patients with pityriasis alba was 2, whereas in the patients with atopic dermatitis it was 4, with a statistically significant difference between them. A cutoff point of 3 cells/square inch was established to differentiate pityriasis alba from atopic dermatitis, with 80% sensibility and 90% specificity. CONCLUSION: We believe that pityriasis alba and atopic dermatitis should be considered different clinical forms within the spectrum of atopic disease, in which sun radiation plays an important role by modulating the progression of the disease. .

Detection of factor XIII-A is a valuable tool for distinguishing dendritic cells and tissue macrophages in granuloma annulare and necrobiosis lipoidica.

BACKGROUND: Factor XIII subunit A (FXIII-A) is used as a diagnostic marker in a wide range of dermatological diseases ranging from inflammatory lesions to malignancies, although neither the cell types responsible for its expression nor the mechanism(s) resulting in its local accumulation in pathological conditions have been characterized. OBJECTIVE: In this study, we aimed to gain information on the cells showing an immunohistochemical reaction for FXIII-A and answer the question whether macrophages and/or dendritic cells are labelled for FXIII-A. METHODS: We carried out our studies on samples of granuloma annulare (GA) and necrobiosis lipoidica (NL), the prime examples for granulomatous skin lesions with a non-infectious background in which extracellular matrix remodelling is a key feature without any sign of malignant transformation. We used markers for macrophages and dendritic cells in combination with the detection of FXIII-A in double labelling immunohistochemical reactions. RESULTS: We demonstrated that FXIII-A positivity clearly distinguishes macrophages (CD163+/FXIII-A+) from dendritic cells (CD11c+/FXIII-A-) not only in the normal dermis as previously described by Zaba et al. (J Clin Invest 2007; 117: 2517-2525) but also in the pathological conditions of GA and NL. Detecting the expression of DC-SIGN/CD209 and mannose receptor molecules on FXIII-A+ macrophages we confirmed that FXIII-A is expressed in the alternatively activated macrophages. However, while DC-SIGN/CD209 was invariably expressed on FXIII-A+ cells both in normal and pathological conditions of GA/NL (98.7% vs. 93.5/96%), mannose receptor was only partially coexpressed with FXIII-A (94.8% vs. 74.7/52.2%), suggesting that FXIII-A+ macrophages do not represent a homogenous population. CONCLUSIONS: FXIII-A selectively marks macrophages and distinguishes them from dendritic cells. The presence of FXIII-A is not a disease-specific marker but indicates a possible common mechanism of macrophage activation in various dermatological diseases.

Immunohistochemical markers in fibrohistiocytic lesions: factor XIIIa, CD34, S-100 and p75.

BACKGROUND: The distinction between dermatofibroma (DF), dermatofibrosarcoma protuberans (DFSP), and other benign and malignant cutaneous spindle cell lesions frequently requires immunohistochemical staining. CD34 and factor XIIIa are the most commonly used immunostains; however, they may exhibit aberrant expression and introduce the potential for misdiagnosis. There is some data supporting that p75 and S100A6 may be additional helpful immunohistochemical markers. METHODS: We undertook a large case series examining the use of CD34 and factor XIIIa as well as p75 and S100A6 in DF, cellular DF, DFSP, indeterminate fibrohistiocytic lesion, and scar. RESULTS: As expected, CD34 stained DFSP, although it was usually negative in DF. Factor XIIIa was generally positive in DF and negative in DFSP. There were exceptions in both cases of DF and DFSP. S100A6 was routinely negative in all entities studied. P75 was negative in all cases except DFSP, approximately half of which showed weak and/or patchy positivity. CONCLUSIONS: We conclude that to date, CD34 and factor XIIIa remain the most reliable immunohistochemical markers for DF and DFSP.

Interferon-γ, interleukins-6 and -4, and factor XIII-A as indirect markers of the classical and alternative macrophage activation pathways in chronic periodontitis.

BACKGROUND: Macrophages account for 5% to 30% of the inflammatory infiltrate in periodontitis and are activated by the classic and alternative pathways. These pathways are identified by indirect markers, among which interferon (IFN)-γ and interleukin-6 (IL)-6 of the classic pathway and IL-4 of the alternative pathway have been studied widely. Recently, factor XIII-A (FXIII-A) was reported to be a good marker of alternative pathway activation. The aim of this study is to determine the macrophage activation pathways involved in chronic periodontitis (CP) by the detection of the indirect markers IFN-γ, IL-6, FXIII-A, and IL-4. METHODS: Biopsies were taken from patients with CP (n = 10) and healthy individuals (n = 10) for analysis of IFN-γ, IL-6, IL-4, and FXIII-A by Western blot (WB), immunohistochemistry (IHC), and enzyme-linked immunosorbent assay (ELISA). The same biopsies of healthy and diseased gingival tissue were used, and the expressions of these markers were compared between healthy individuals and those with CP. RESULTS: The presence of macrophages was detected by CD68+ immunohistochemistry and their IFN-γ, IL-6, IL-4, and FXIII-A markers by WB, IHC, and ELISA in all samples of healthy and diseased tissue. IL-6, IL-4, and FXIII-A were significantly higher in patients with CP, whereas FXIII-A was higher in healthy individuals. CONCLUSION: The presence of IFN-γ, IL-6, IL-4, and FXIII-A in healthy individuals and in patients with CP suggests that macrophages may be activated by both classic and alternative pathways in health and in periodontal disease.

[Fibrous papules of the face: a retrospective anatomoclinical study of 283 cases]. / Papules fibreuses du visage: une étude anatomo-clinique rétrospective de 283 cas.

BACKGROUND: Fibrous papules of the face are frequent benign lesions seen in the nasal and perinasal region. Their clinical aspect is indistinct and the histological signs are sometimes mild or possibly misleading in the case of atypical forms. We carried out a retrospective study of 283 fibrous papules diagnosed at our histology laboratory. The goal of this study was to characterize this type of frequent but occasionally unrecognized lesion. PATIENTS AND METHODS: We performed a retrospective study of fibrous papules of the face diagnosed in the dermatopathology laboratory of our dermatology centre between January 2002 and December 2011. The study concerned the clinical information noted in the examination request and the morphological abnormalities seen at optical microscopy. An immunohistological study of factor XIIIa was performed in selected cases. RESULTS: The fibrous papules of the face came from 129 men and 154 women aged between 18 and 90 years (mean: 46 years). Two hundred and thirty-seven (83.7%) lesions were taken from the nasal region and none were taken from anywhere other than the face. The clinically mentioned diagnoses varied. A diagnosis of fibrous papule of the face was stated in 42% of cases, and the main differential diagnoses were nevus (stated in 34% of cases) and basal cell carcinoma (stated in 14% of cases). The fibrous papules were classic in 85.5% of cases. We observed 6 variants of fibrous papule: hypercellular, inflammatory, pleomorphic, pigmented, clear-cell and granular-cell types. Immunohistochemistry of factor XIIIa was positive in all cases except clear-cell fibrous papules. DISCUSSION: This study shows that despite their frequency, these lesions often go unrecognized, since the hypothesis of a fibrous papule of the face was mentioned in fewer than 50% of cases at the time of biopsy. Diagnosis is often made by the histopathologist, who may be misled by some rare types. The principal differential diagnoses are nevus and basal cell carcinoma, thus warranting methodical histological analysis of all pieces.

Dermal dendritic cell population and blood vessels are diminished in the skin of systemic sclerosis patients: relationship with fibrosis degree and disease duration.

Recent studies have suggested that the number of dermal dendritic cells is altered in the skin of patients with scleroderma and that these cells may have an important role in the pathogenesis of this disease. There is also a belief that insufficient blood flow to the affected organs may also be responsible for the disease. Our aim was to quantify CD34+ cells, factor XIIIa cells, and blood vessels in the skin of patients with systemic sclerosis and to correlate these data with fibrosis degree and duration of disease. Paraffin-embedded skin sections from patients with systemic sclerosis and from healthy subjects were immunolabelled with antibodies against CD34+ and factor XIIIa. Cells and blood vessels were quantified in the papillary and reticular dermis. Both, the number of CD34+ cells and factor XIIIa cells in the skin of patients with systemic sclerosis were reduced. The reduction of these cell types preceded the appearance of intense fibrosis, suggesting that fibrosis is not responsible of this phenomenon. Blood vessel volume and surface density were also reduced in the skin of systemic sclerosis patients. This reduction was also noted early in the evolution of the disease. Our results suggest that CD34+ cells and factor XIIIa cells may contribute to normal regulation of extracellular matrix assembly. We confirmed the observation that capillary density is diminished in scleroderma skin.

Presencia de marcadores de las vías de activación de los macrófagos en periodontitis crónica / Presence of markers of activation pathways of macrophages in chronic periodontitis

La periodontitis crónica es una patología infecciosa, causada por un complejo de especies bacterianas, que afecta principalmente los tejidos de inserción de los dientes. La respuesta inmune-inflamatoria producida se caracteriza por la presencia de un infiltrado inflamatorio, en el cual los macrófagos representan entre 5 al 30 por ciento. Es sabido que los macrófagos se activan mediante dos vías: Clásica y Alterna, caracterizadas por la presencia de marcadores indirectos: IFN-y e IL-6 para la vía clásica e IL-4 para la vía alterna, ampliamente abordados. Recientemente, se ha descrito a la subunidad A del factor XIII de la coagulación (FXIII-A) como un buen marcador de la vía alterna. El objetivo de este estudio consiste en determinar la presencia de IFN-y, IL-6, FXIII-A e IL-4 como marcadores de las vías de activación de los macrófagos, en pacientes con periodontitis crónica. Para tal efecto, se realizó inmunohistoquímica y Western-Blot para los cuatro marcadores junto a CD-68, marcador de macrófagos, en 18 biopsias de tejido periodontal sano y 18 con periodontitis crónica. Se detectó la presencia de IFN-y, IL-6, IL-4 y FXIII-A junto a CD68+, en todas las muestras de pacientes sanos y con periodontitis. Los resultados obtenidos sugieren que al estar presente IFN-y, IL-6, IL-4 y FXIII-A, los macrófagos se activarían a través de ambas vías, lo cual, produciría una respuesta tanto proinflamatoria (Th1) como antinflamatoria (Th2). Son necesarios más estudios para determinar si existe una vía preferencial de activación.

Periodontitis is a chronic infectious disease caused by a bacterial species complex, which affects mainly the insertion tissues of the teeth. The immune-inflammatory response produced is characterized by an inflammatory infiltrate in which macrophages represent between 5 to 30 percent. It is known and has been widely discussed that macrophages are activated in two ways: Classical and Alterna, characterized by the presence of indirect markers: IFN-y and IL-6 for the classical pathway and IL-4 for the alternative pathway. Recently the subunit A of the clotting factor XIII (FXIII-A) has been described as a good marker of the alternative pathway. The objective of this study is to determine the presence of IFN-y, IL-6, IL-4 and FXIII-A as markers of the macrophage activation pathways in patients with chronic periodontitis. To this end, we performed immunohistochemistry and Western blot for the four markers with CD68 macrophage marker, in 18 healthy periodontal tissue biopsies and 18 with chronic periodontitis. We detected the presence of IFN-y, IL-6, IL-4 and FXIII-A with CD68 +, in all samples of healthy patients and periodontitis. The results suggest that when present, IFN-y, IL-6, IL-4 and FXIII-A, activate macrophages through both routes, which would produce a proinflammatory response (Th1) as antiinflammatory (Th2). Further studies are necessary to determine whether there is a preferential pathway activation.

D2-40, a novel immunohistochemical marker in differentiating dermatofibroma from dermatofibrosarcoma protuberans.

The distinction between dermatofibroma, particularly cellular variant, and dermatofibrosarcoma protuberans in excisional biopsies is usually straightforward. However, a separation between the two may be sometimes challenging, especially in superficial biopsies. Although factor XIIIa and CD34 immunostains are useful in differentiating dermatofibroma and dermatofibrosarcoma protuberans in most instances, focal CD34 positivity may be seen in cellular fibrous histiocytoma. Some cases reveal overlapping immunostain results. D2-40 identifies a 40-kDa O-linked sialoglycoprotein present on a variety of tissues including testicular germ cell tumors as well as lymphatic endothelium. In this study, we investigated the utility of D2-40 in separating dermatofibroma from dermatofibrosarcoma protuberans and compared the results with other commonly used immunostains. Fifty-six cases of dermatofibroma (including six cellular variant) and 29 cases of dermatofibrosarcoma protuberans were retrieved from the archives of Department of Anatomic Pathology at Sunnybrook Health Sciences Center in University of Toronto. We applied factor XIIIa, CD34, and monoclonal mouse anti-D2-40 immunostains to formalin-fixed, paraffin-embedded tissue sections. All 56 (100%) cases of dermatofibroma demonstrated strong and diffuse immunoreactivity to D2-40 in the spindle cells and stroma. Similarly, factor XIIIa showed strong and diffuse positivity in the spindle cells. Nearly all dermatofibromas were negative for CD34 except one case revealing focal positivity. None of dermatofibrosarcoma protuberans cases were labeled by D2-40, although four cases showed weak and patchy background staining in contrary to diffuse, strong, and crisp staining seen in dermatofibromas. Our results indicate that D2-40 seems to be a sensitive immunohistochemical marker for dermatofibromas, including cellular variant. Focal and faint D2-40 staining may be seen in the stroma of dermatofibrosarcoma protuberans. Our findings suggest that D2-40 can be used as a complementary immunostain to factor XIIIa and CD34 in problematic and challenging cases on superficial biopsies.

Oral lichen planus and dermal dendrocytes.

INTRODUCTION: Oral lichen planus (OLP) is a relatively common inflammatory disease with a wide range of clinical forms. Its pathogenesis has not been fully elucidated although it is known to be mediated by lymphocytes with the participation of cytokines and other inflammatory cells, including type I and type II dermal dendrocytes (DD) (factor XIIIa+ DD and CD34+ DD, respectively). OBJECTIVES: To describe the presence and tissue distribution of these cells, through immunohistochemistry, in 23 specimens from patients with clinical and histopathological criteria of OLP. RESULTS: Factor XIIIa+ DD were mainly located in the superficial dermis (p < 0.0001) as opposed to the deep submucosa. These cells were abundant throughout the dermal-epidermal junction and closely related to lymphocyte infiltration. Moreover, factor XIIIa+ DD were also found in the epithelium and deep dermis. CD34+ DD were distributed mostly to the deep dermis directly below the lymphocyte infiltrate with few cells in the subepithelial region. CONCLUSIONS: DD were present in OLP, with distinct tissue distributions. Factor XIIIa+ DD were predominant in the superficial dermis while CD34+ DD could be found mostly in the deep dermis. These findings suggest that DD, and those positive for factor XIIIa+ in particular in view of their ability to express intercellular adhesion molecule-1 (ICAM-1) and tumor necrosis factor alpha (TNF-alpha), may play an important role in pathogenesis of OLP.