High Risk of Non-Melanoma Skin Cancer in Actinic Keratosis Patients with Skin of Color: A Nationwide Register-Based Cohort Study.

INTRODUCTION: Actinic keratoses (AKs) are rough, scaly patches from UV exposure, increasing the risk of non-melanoma skin cancer (NMSC). This study examines AK incidence in Korea and its role as a risk factor for NMSC. METHODS: A retrospective nationwide register-based cohort study analyzed 2,917 AK patients and 14,585 controls from 2002 to 2019. Patients diagnosed with AK were followed until NMSC occurrence, death, emigration, or December 2019. RESULTS: AK incidence reached 44.8 per 100,000 person-years in 2019. The adjusted hazard ratio for NMSC in AK patients was 8.91 (95% confidence interval, 5.72-13.90). Higher NMSC risk was observed in female AK patients, those under 60 years, and those with lower income levels. The 16-year cumulative incidence of NMSC was 4.19% in AK patients versus 0.44% in controls. CONCLUSION: AK significantly increases the risk of NMSC in Koreans, highlighting the need for tailored surveillance and treatment strategies.

Single-center real-world treatment outcomes of ablative fractional laser-assisted photodynamic therapy for actinic keratosis.

BACKGROUND: Among various treatment modalities of actinic keratosis (AK), ablative fractional laser-assisted photodynamic therapy (fractional PDT) has shown higher efficacy despite shorter incubation time. However, there are lack of real-world studies on the therapeutic response of ablative PDT for AK and the factors that can predict the therapeutic response. PURPOSE: The aim of this study was to analyze the association between clinical characteristics and treatment outcomes of fractional PDT. METHODS: One hundred fifty-six patients who were histologically diagnosed with AK and treated with fractional PDT were retrospectively reviewed. The Kruskal-Wallis test was used to compare treatment session differences according to grades. RESULTS: In multivariate analysis, the grade 2 category tended to be more clinically nonresponders than the grade 1 (OR, 5.17; 95% CI, 1.011-26.439; p = .048) and the group treated four or more times with ablative fractional laser-assisted PDT were more likely to show no response compared with the single treatment session group (OR, 8.78; 95% CI, 1.355-56.874; p = .023). Treatment sessions were significantly lower in grade 1 (1.72 ± 0.63, mean ± SD) when compared to grades 2 and 3, respectively (2.17 ± 0.76; 2.60 ± 1.60, mean ± SD). Recurrence was highest in grade 2, and most of them occurred after 1 year. CONCLUSION: On average, two treatment sessions are sufficient for AK lesions, but the thicker the lesion, the more treatment sessions may be required. Although there are relatively smaller number of grade 3 patients were included, recurrence was more frequent in higher grade of AK category, which needs special attention to thicker lesions.

Comparison of Melanocyte-Associated Immunohistochemical Markers in Acral Lentiginous Melanoma and Acral Benign Nevi.

ABSTRACT: Acral lentiginous melanoma (ALM) is a relatively rare clinicopathologic subtype of cutaneous malignant melanoma, but it is the most common type of melanoma among Asians. Although the research to identify immunohistochemical (IHC) markers to differentiate nevi from melanoma is being conducted, specific markers for ALM are not well-known. Therefore, we aimed to analyze and compare the differences in the expression of melanocyte-associated IHC markers between ALM and acral benign nevi (ABN). Two independent groups of 53 and 19 paraffin-embedded specimens (from patients with pathologically confirmed ALM and ABN, respectively) were subjected to IHC staining for MART-1, preferentially expressed antigen in melanoma (PRAME), SOX10, HMB-45, Ki-67, and p16. We performed a quantitative analysis of PRAME, SOX10, KI-67, and p16 expression and gradient pattern analysis of HMB-45 expression for each specimen. The PRAME (60.1% and 28.5%, P < 0.05) and Ki-67 (7.8% and 3.5%, P < 0.05) expression levels were significantly higher in the ALM group than in the ABN group. The p16 expression was significantly lower (14.2% and 19.4%, P < 0.05), and the absence of HMB-45 gradient was more frequent in the ALM group than in the ABN group. However, no statistical significance was noted in SOX10 (54.8% and 44.7%). Receiver operating characteristic curves showed that PRAME had the highest area under the curve value. In summary, among various IHC markers, PRAME was the most valuable marker for the diagnosis of ALM; however, further large-scale studies are needed to validate these findings.

Pigmented contact dermatitis and hair dyes: A retrospective case-control multicentre study in Korea.

BACKGROUND: Pigmented contact dermatitis (PCD), a rare variant of non-eczematous contact dermatitis, is clinically characterized by sudden-onset brown or grey pigmentation on the face and neck. It is hypothesized to be caused by repeated contact with low levels of allergens. OBJECTIVES: This study evaluated the risk of using hair dyes in patients with PCD in Korea. METHODS: A total of 1033 PCD patients and 1366 controls from 31 university hospitals were retrospectively recruited. We collected and analysed the data from the patient group, diagnosed through typical clinical findings of PCD and the control group, which comprised age/sex-matched patients who visited the participating hospitals with pre-existing skin diseases other than current allergic disease or PCD. RESULTS: Melasma and photosensitivity were significantly more common in the control group, and a history of contact dermatitis was more common in the PCD group. There were significantly more Fitzpatrick skin type V participants in the PCD group than in the control group. There was no significant difference in sunscreen use between the groups. Using dermatologic medical history, Fitzpatrick skin type and sunscreen use as covariates, we showed that hair dye use carried a higher PCD risk (odds ratio [OR] before adjustment: 2.06, confidence interval [CI]: 1.60-2.65; OR after adjustment: 2.74, CI: 1.88-4.00). Moreover, henna users had a higher risk of PCD (OR before adjustment: 5.51, CI: 4.07-7.47; OR after adjustment: 7.02, CI: 4.59-10.74), indicating a significant increase in the risk of PCD with henna dye use. Contact dermatitis history was more prevalent in henna users than in those using other hair dyes in the PCD group (17.23% vs. 11.55%). CONCLUSION: Hair dye use is a risk factor for PCD. The risk significantly increased when henna hair dye was used by those with a history of contact dermatitis.

Can we predict postinflammatory hyperpigmentation after laser treatment based on dermoscopic findings of solar lentigo?

Solar lentigo (SL) commonly occurs as hyperpigmented macules in areas exposed to ultraviolet radiation. It typically shows an increased number of melanocytes in the basal cell layer of the skin, with or without elongated rete ridges. This retrospective study aimed to evaluate the characteristic dermoscopic patterns, reflecting different histopathological features, which might be valuable in predicting the possibility of postinflammatory hyperpigmentation (PIH) occurring after laser treatment. In total, 88 Korean patients diagnosed with biopsy-proven SL (a total of 90 lesions were diagnosed) between January, 2016 and December, 2021 were included. Histopathological patterns were classified into six categories. Dermoscopic features were classified into six categories. Pseudonetwork pattern and rete ridge elongation showed a statistically significant negative correlation. This means that a flatter epidermis is likely to manifest as a pseudonetwork pattern. The erythema pattern showed a significant positive correlation with interface changes and inflammatory infiltration. Bluish-gray granules (peppering), a characteristic dermoscopic finding, showed significant positive correlations with interface changes, inflammatory infiltration, and dermal melanophages. Clinicians considering laser treatment for patients with SL should perform dermoscopic tests before treatment. The pseudonetwork relates to flattened epidermis and fewer Langerhans cells; thus, a lower remission of PIH after laser treatment might be expected. If bluish-gray granules or erythema are observed, inflammatory conditions are likely to be involved. In such cases, regression of the inflammatory response through drug therapy, such as topical corticosteroids, should be a priority option before laser treatment.

A prospective study to evaluate the treatment effect of pulsed dye laser on thyroidectomy hypertrophic scars using 3D imaging analysis.

OBJECTIVES: The pulsed dye laser (PDL) is an effective modality for preventing and improving hypertrophic scars (HSs). However, the heterogeneity of the parameter settings of the laser and subjective scar assessment methods used in most studies resulting in uncertainty with treatment plans. Therefore, we investigated the treatment effect of the PDL (V-beam; Candela Laser Corporation) on HSs in post-thyroidectomy patients using three-dimensional imaging analysis and intended to provide a systemic and optimal treatment protocol. METHODS: Nineteen patients with HS after thyroidectomy underwent eight treatment sessions with the 595 nm PDL (with the dose gradually increased by 0.5 J/cm2 ) at 4- to 6-week intervals. Patients with an elevated lesion also received intralesional corticosteroid (ICS) treatment. After every two treatment sessions, we assessed the patients' HS using the Vancouver Scar Scale (VSS), a patient satisfaction questionnaire, and with a three-dimensional (3D) skin imaging device (Antera 3D™; Miravex Limited). RESULTS: In repeated-measures analysis of variance, the mean VSS and patient satisfaction significantly improved (p < 0.001), with significant differences in these values observed until the sixth and eighth treatment sessions, respectively. In the quantitative analysis using Antera 3D™, the mean height, pigmentation, and vascularity scores were observed to be significantly improved (p < 0.001). Significant differences in these values were observed until the fourth, second, and eighth treatment sessions, respectively. Subgroup analysis according to ICS treatment showed no significant differences in scar characteristics between those with and without ICS treatment. CONCLUSIONS: In this study, we found that the PDL was effective in reducing scar height, vascularity, and pigmentation in patients with thyroidectomy HS using 3D imaging analysis. Furthermore, we have suggested a cost-effective treatment plan with the 595 nm PDL.

Photobiomodulation therapy with an 830-nm light-emitting diode for the prevention of thyroidectomy scars: a randomized, double-blind, sham device-controlled clinical trial.

This randomized, double-blind, and sham device-controlled trial aimed to evaluate the efficacy and safety of home-based photobiomodulation therapy using an 830-nm light-emitting diode (LED)-based device for the prevention of and pain relief from thyroidectomy scars. Participants were randomized to receive photobiomodulation therapy using an LED device or a sham device without an LED from 1 week postoperatively for 4 weeks. Scars were assessed using satisfaction scores, the numeric rating scale (NRS) score for pain, Global Assessment Scale (GAS), and Vancouver Scar Scale (VSS) scores. The scars were also assessed using a three-dimensional (3D) skin imaging device to detect color, height, pigmentation, and vascularity. Assessments were performed at the 1-, 3-, and 6-month follow-ups. Forty-three patients completed this trial with 21 patients in the treatment group and 22 patients in the control group. The treatment group showed significantly higher patient satisfaction and GAS scores and lower NRS and VSS scores than the control group at 6 months. Improvements in color variation, height, pigmentation, and vascularity at 6 months were greater in the treatment group than in the control group, although the differences were not significant. In conclusion, early application of 830-nm LED-based photobiomodulation treatment significantly prevents hypertrophic scar formation and reduces postoperative pain without noticeable adverse effects.

Development of evidence-based consensus on critical issues in the management of patients with vitiligo: A modified Delphi study.

BACKGROUND/PURPOSE: Vitiligo remains a major challenge in dermatology. However, much of the treatment remains unclear, because little evidence is available. We sought to answer some critical questions pertaining to management of vitiligo patients. METHODS: A modified Delphi process among 31 vitiligo experts was conducted. A total of 12 clinical vitiligo treatment questions without clear answers were collected via a vote. To address each question, two members performed systematic literature reviews and prepared draft statements along with the levels of evidence and strength of recommendation. After reviewing the draft, all expressed their extent of agreement from 1 (strong disagreement) to 9 (strong agreement) for each item. The drafts were revised to reflect suggested comments. Discussion continued until all members agreed with the ultimate decision. RESULTS: The consensus process was completed after five rounds. We identified the best answers to 12 key questions, including issues on long-term phototherapy, systemic and topical corticosteroids, topical calcineurin inhibitors, immunosuppressants, excimer laser treatment, and surgical interventions. CONCLUSION: This consensus would complement current guidelines and aid both physician and patient decision-making in the treatment of vitiligo.

Eruptive Xanthoma With Dermal Mucin Deposition.

ABSTRACT: Xanthomas present clinically as eruptive, tuberoeruptive, tuberous, tendinous, or planar forms. Among these, eruptive xanthoma (EX) is characterized by sudden development of multiple, red-to-yellow papules, each less than 5 mm in diameter, on the extensor surface of the extremities and the buttock area. EX is often associated with severe hypertriglyceridemia, underlying diabetes, obesity, or excessive alcohol intake. Histologically EX is characterized by foamy cells, which are lipid-laden macrophages surrounded by lymphoid cells, histiocytes, and neutrophils; however, mucin deposition is not a typical feature. Herein, we report a rare case of xanthoma with diffuse, abundant mucin deposition.

Hypopigmented Mycosis Fungoides Mimicking Vitiligo.

ABSTRACT: Hypopigmented mycosis fungoides (HMF) is a clinical variant of MF with a presentation similar to other hypopigmented diseases, especially vitiligo. In this article, we report an adult case of HMF mimicking vitiligo. A 53-year-old man presented with an asymptomatic well-defined focal and hypopigmented patch with erythematous to brownish macules on the flank which had been developing over several months without other cutaneous findings. He had no past medical or trauma history. Skin biopsy from the hypopigmented patch indicated a slightly band-like, superficial dermal infiltrate of lymphocytes with mild cytologic atypia and epidermotropism. Fontana-Masson and Mart-1 stains showed a decrease in the epidermal pigment and the number of basal melanocytes. In addition, CD4 and CD8 stains were positive, predominantly the CD8 stain, and loss of CD7 stain was noted in the epidermal atypical lymphocytes. A T-cell receptor gene rearrangement study from the hyperpigmented area showed monoclonality. Finally, we diagnosed the patient with HMF. After about 17 months of treatment with narrow-band ultraviolet B, the hypopigmented lesion had notably improved in both the clinical and histological aspects. The clinical appearance of our case was similar to vitiligo while clinical improvement was also exceptionally similar to the skin findings from follicular repigmentation after narrow-band ultraviolet B treatment in vitiligo. Therefore, dermatologists should consider the clinical differential diagnosis of HMF in patients with an asymptomatic hypopigmentation, especially in dark-skinned Asian patients.

Histopathological Features of Riehl Melanosis.

Histological features of Riehl melanosis have rarely been compared between lesional and perilesional normal skin and have not been precisely described using quantitative or immunohistochemical analysis or electron microscopic findings. To investigate the histopathological and immunohistochemical features of lesional and perilesional normal skin of patients with Riehl melanosis, we retrospectively evaluated the electronic medical records and skin biopsy specimens of 48 patients with Riehl melanosis. In addition, electron microscopy was performed on 1 case. Fontana-Masson staining for melanin and immunohistochemical staining for Melan-A, NKI/beteb, tyrosinase, and microphthalmia-associated transcription factor were performed. Although the difference was statistically insignificant, melanin pigment was increased in the epidermis of lesional skin compared with that of perilesional normal skin in patients. The number of melanocytes and their activity were significantly increased in lesional epidermal skin. Melanin pigment was also significantly increased in the lesional dermis. Pigmentary incontinence, basal cell liquefaction, dilated vessels, epidermal spongiosis, and colloid bodies were found in the lesional skin as well as in the perilesional normal skin to a lesser extent. Under electron microscopy of 1 randomly selected subject, many fibrocytes contained numerous melanosome particles in the cytoplasm of the lesional dermis. In perilesional normal skin, fibroblasts also contained melanosome particles; however, the number of melanosome-containing cells was less than that in lesional skin. Riehl melanosis is characterized by increased epidermal melanocytes and pigmentation, primarily involving the dermis, with histologically typical changes at the interface. Unlike that in other pigmentary diseases, most perilesional normal-appearing skin in Riehl melanosis also shows typical histopathological changes, although to a lesser extent.

Two histopathological patterns of postinflammatory hyperpigmentation: epidermal and dermal.

BACKGROUND: Postinflammatory hyperpigmentation (PIH) commonly occurs, but the histopathological features are not well characterized. METHODS: A total of 21 PIH patients' medical charts were reviewed. Punch biopsies from lesional and perilesional normal skin were performed. Sections were stained with hematoxylin-eosin, Fontana-Masson, NKI/beteb, microphthalmia-associated transcription factor (MITF), CD68, c-kit, factor XIIIa, MMP-2 and MMP-9. RESULTS: Fontana-Masson-stained sections suggested two obvious PIH groups: epidermal (13 cases) and dermal (8 cases) pigmentation. The epidermal pigment group had increased epidermal basal pigmentation. The dermal pigment group had marked pigmentation within the upper dermis and decreased epidermal pigmentation. More intense perivascular lymphocytic infiltration was observed in the dermal pigment group. NKI/beteb levels were increased in lesional skin in both groups. The numbers of MITF+ melanocytes were not different between lesional and perilesional normal skin in either group. The expression of CD68 and c-kit was significantly higher in the dermis of lesional skin than in normal skin in the dermal pigment group. MMP-2 expression was upregulated in lesional skin in both groups. CONCLUSION: PIH patients can be classified into two histopathological groups: epidermal and dermal pigmentation. The dermal pigment group showed decreased levels of epidermal pigmentation. This study provides histopathological information that can improve the treatment of PIH.

Cutaneous Lymphoma in Korea: A Nationwide Retrospective Study.

The epidemiological and clinicopathological features of cutaneous lymphoma may vary by geographical area. However, only a few large-scale epidemiological studies of cutaneous lymphoma have been performed, mainly in the USA and Europe. This aim of this study was to determine the recent characteristics of cutaneous lymphoma in Korea according to the WHO/EORTC classification. A total of 422 patients with newly diagnosed cutaneous lymphoma from January 2009 to December 2013 comprising 293 cases of mature T-cell and natural killer (NK)-cell lymphoma and 39 cases of mature B-cell lymphoma were retrospectively reviewed. The incidence of mature B-cell lymphoma was lower in Korea than in Europe and the USA. Diffuse large B-cell lymphoma was more prevalent in Korea than in Western countries. The incidence of extranodal NK/T-cell lymphoma, nasal-type was higher in Korea than in Western countries and Japan.

Prevention of Thyroidectomy Scars in Asian Adults With Low-Level Light Therapy.

BACKGROUND: Abnormal wound-healing after thyroidectomy with a resulting scar is a common dermatologic consultation. Despite many medical and surgical approaches, prevention of postoperative scars is challenging. OBJECTIVE: This study validated the efficacy and safety of low-level light therapy (LLLT) using an 830/590 nm light-emitting diode (LED)-based device for prevention of thyroidectomy scars. METHODS AND MATERIALS: Thirty-five patients with linear surgical suture lines after thyroidectomy were treated with 830/590 nm LED-LLLT. Daily application of 60 J/cm (11 minutes) for 1 week starting on postoperative day 1 was followed by treatment 3 times per week for 3 additional weeks. The control group (n = 15) remained untreated. Scar-prevention effects were evaluated 1 and 3 months after thyroidectomy with colorimetric evaluation using a tristimulus-color analyzer. The Vancouver Scar Scale (VSS) score, global assessment, and a subjective satisfaction score (range: 1-4) were also determined. RESULTS: Lightness (L*) and chrome values (a*) decreased significantly at the 3-month follow-up visit in the treatment group compared with those of controls. The average VSS and GAS scores were lower in the treatment group, whereas the subjective score was not significantly different. CONCLUSION: Light-emitting diode based LLLT treatment suppressed the formation of scars after thyroidectomy and could be safely used without noticeable adverse effects.

Differentiating confluent and reticulated papillomatosis from acanthosis nigricans.

BACKGROUND: Confluent and reticulated papillomatosis (CRP) is an uncommon dermatosis with a reticular pattern. As differentiation between CRP and benign acanthosis nigricans (AN) can be challenging because of their similar clinicopathological features, we aimed to distinguish the two diseases. METHODS: We retrospectively reviewed the clinical characteristics of 60 CRP and 30 AN patients. Histological examinations were conducted on 33 CRP and 30 AN lesions. RESULTS: While CRP was concentrated on the trunk, AN mostly appeared in the axilla. In the AN group, the number of obese patients was higher, and acanthosis and papillomatosis were more evident. In both group, increases in Ki-67 and keratin 16 expression were similar. Bacterial infection was detected at a higher rate in CRP lesions than in AN lesions.AN lesions had greater pigmentation because of a high number of melanocytes than CRP lesions. CONCLUSIONS: The location of skin lesions and body mass index are the main clinical factors that enable differentiation between CRP and AN. The epidermal histological changes in CRP are milder than those in AN. AN lesions also showed a greater degree of pigmentation and melanocytic proliferation.

Fractional carbon dioxide laser-assisted photodynamic therapy for patients with actinic keratosis.

BACKGROUND/PURPOSE: A relatively long incubation time is needed for photosensitizer absorption in conventional photodynamic therapy (PDT) for actinic keratosis (AK). The use of ablative CO2 fractional lasers (AFXLs) to increase drug delivery could shorten the incubation time. Here, we aimed to compare the efficacy between AFXL-assisted PDT with a short incubation time and conventional PDT for AK. METHODS: Patients with histopathologically confirmed facial AK were randomly divided into two groups. The lesions were histopathologically classified into grades I-III. In the AFXL-assisted PDT group, an ablative fractional laser was used for pretreatment, prior to the application of methyl aminolevulinate, with an incubation time of 90 min. Irradiation was performed with a 630-nm light-emitting diode. In the conventional PDT group, the incubation time was 180 min. All the patients received two rounds of PDT at 2-week intervals and underwent clinical or histological evaluation at 10 weeks after the first PDT course. RESULTS: Twenty-two patients underwent conventional PDT and 24 patients underwent AFXL-assisted PDT. Thirty-four AKs were included in the conventional PDT group, and 35 AKs were included in the AFXL-assisted PDT group. The clearance rate was 64.7% in the conventional PDT and 71.4% in the AFXL-assisted PDT group; no significant differences in the clearance rate were noted between the groups (P = 0.55). The clearance rates for each grade also did not significantly differ between the two groups. CONCLUSIONS: The use of AFXL before PDT reduced the incubation time, but yielded similar treatment efficacy as compared to conventional PDT.

Changes of epidermal thickness in vitiligo.

The stratum corneum and epidermal pigmentation have protective roles against ultraviolet radiation. Because vitiligo skin lacks melanocytes and has no potential to produce pigment, some studies suggested that the epidermis in vitiligo skin is thicker than in normal skin. However, only a few studies investigated epidermal thickness changes in vitiligo, and some of these had relatively small sample sizes. Thus, this study aimed to compare epidermal thickness between vitiligo skin and adjacent normal-appearing skin in a large cohort. Photos of hematoxylin and eosin­stained slides of vitiligo skin and adjacent normal-appearing skin were taken under a microscope. The thicknesses of the stratum corneum, viable epidermis, and full epidermis were then measured by a computerized image analyzer. A total of 206 patients (412 sections) were included. There were significant differences between vitiligo skin and adjacent normal-appearing skin in the thickness of the stratum corneum (P = 0.009), viable epidermis (P = 0.001), and total epidermis (P = 0.001). An analysis comparing skin biopsied from a sun-exposed area versus a sun-protected area showed that the stratum corneum, viable epidermis, and total epidermis were significantly thicker in vitiligo skin than in normal-appearing skin in sun-exposed areas (P < 0.05), but not in sun-protected areas. We revealed that the epidermis was thicker in vitiligo skin than in normal-appearing skin, especially on sun-exposed skin, and that this may represent a photoprotective role compensating for absent pigmentation.

Nipple eczema, an indicative manifestation of atopic dermatitis? A clinical, histological, and immunohistochemical study.

Nipple eczema exhibits as a minor manifestation of atopic dermatitis (AD) or occurs as a single skin symptom on the nipple. To characterize the relationship between nipple eczema and AD, a clinical evaluation and an immunohistochemical study were performed. All cases of nipple eczema were confirmed histopathologically. We divided the patients with nipple eczema into 2 groups, namely, those with AD and those without AD, and compared several clinical features. Upon histological examination, the degree of inflammation was subjectively graded as mild, moderate, or severe by 2 separate investigators. Immunohistochemical stainings were performed by using antiinterleukin (IL)-4, anti-IL-13, anti-CD4, and anti-CD8 antibodies, and the results were scored semiquantitatively. In 43 cases evaluated, 12 were nipple eczema with AD. The clinical analysis and histological examination showed no significant differences between the groups. There were consistent findings of IL-4 expressions throughout the epidermis and IL-13 expression mainly in the perivascular area of the dermis. Although CD4 and CD8 were expressed in the cells in the dermis, CD8 expression was detected in the serocrusts of the epidermis. Expression levels of IL-4, IL-13, CD4, and CD8 exhibited no significant differences between the nipple eczema group with AD and the nipple eczema group without AD. Although nipple eczema may accompany AD, we found no definite differences in the degree or pattern of inflammation and cytokine expression level regardless of whether AD was present or not. Serocrust formation seemed to be mainly a collection of CD8-positive cells.

Expression of follicular helper T-cell markers in primary cutaneous T-cell lymphoma.

The follicular helper T cells (TFH) seemed to be expressed in several subsets of T-cell lymphomas. However, their expression in cutaneous T-cell lymphomas (CTCLs) has been rarely described. We investigated the clinical features, histopathological morphology, and expression of TFH markers in CTCLs. Forty-nine patients (24 men and 25 women) diagnosed with CTCL were examined, 25 patients with mycosis fungoides (MF) and 24 with other CTCLs. Immunohistochemical staining for CD10, Bcl-6, inducible costimulator, CXCL13, and PD-1 were performed. Relation between PD-1 and clinical course in MF was evaluated. PD-1 was detected in 21 of 25 (84.0%) MF cases and in 11 of 24 (45.8%) other CTCL cases. Bcl-6, CXCL13, inducible costimulator, and CD10 were occasionally expressed in most T-cell lymphomas, including MF. The staining for PD-1 was negative in all the MF cases with large-cell transformation. No correlation was observed between disease course and PD-1 expression rate in the MF cases. In conclusion, among the TFH markers, PD-1 was most frequently expressed in CTCL. PD-1 was expressed in most MF. PD-1 expression rates were significantly higher in MF than in other CTCLs.