An 86-year-old Japanese man visited a local doctor with bleeding from a 1-cm black nodule on his right upper arm. Excisional biopsy was performed with a 2 mm margin. The patient was referred to our department with the diagnosis of malignant melanoma. Histologically, there was a basophilic nodular lesion from the epidermis to middle dermis, and a clear zone was seen in the center. In the basophilic nodular lesion, atypical clear cells irregularly proliferated in the lower epidermis. Atypical epithelioid cells with eosinophilic cytoplasm proliferated in the dermis and atypical balloon cells with large, clear, foamy cytoplasm proliferated in the central clear zone. Immunohistochemically, epithelioid cells were positive for S-100 protein, HMB45, and Melan-A, and balloon cells were positive for S-100 protein and Melan-A. A diagnosis of balloon cell melanoma was made. The resected specimen was margin free, and no evidence of metastases was found. Therefore, no additional resection was performed, and the patient was treated by local injections of interferon β. However, 17 months later, a 7-mm pale blue subcutaneous nodule appeared about 3 cm from the center of the scar. Excisional biopsy demonstrated an in-transit metastasis of balloon cell melanoma. There were no ndings of distant metastasis, and local injections of interferon βwere continued. There was no recurrence or metastasis during follow-up ; however, the patient died of pneumonia. Balloon cell melanoma is a rare variant of melanoma, and balloon cells may occur during the progression of melanoma. Skin Research, 22 : 181-186, 2023

A 78-year-old man was referred to our hospital with pain and change in color of his right thumb. At the rst visit, a 10×3.5 mm, yellowish-white, small nodule was found in the periungual region of the right thumb. Based on the symptoms and the clinical course, we initially suspected an acquired horned nail broma, dermatobroma, or pterygium, and performed total resection under local anesthesia. Histopathological examination revealed a cyst covered by epidermal tissue with squamous eddy, and the cyst lumen contained keratinized tissue. We diagnosed him with epidermal cyst around the nail. The total number of epidermal cysts diagnosed at our department between 2017 and 2022 was 208, of which only two epidermal cysts occurred on the nger, including the present case. The mechanism of epidermal cyst formation on the ngers has been suggested to be the embedding of epidermis due to human papilloma virus (HPV) or injury. In this case,histopathological ndings were negative for HPV infection and he had no obvious history of trauma,so we considered the possibility that he did not remember having minor trauma in the past. Although epidermal cysts around the nail are rare, they should be considered when masses are found in the ngers. Skin Research, 22 : 187-191, 2023

The patient was a 88-year-old man who had been diagnosed with Kaposi’s sarcoma and HIV infection nine years before after multiple brownish to purple plaques and nodules on the trunk and limbs. Kaposi’s sarcoma was in complete remission with ART therapy, and HIV virus levels had been below detection sensitivity. He had been aware of a rice-sized black papule on his right sole a month before, which had increased in size during the previous 5 days and become tender. A protuberant lesion was found on his right sole (9 mm×7 mm diameter). The number of CD4 positive cells in the peripheral blood was 300/μl. The nodule was resected on suspicion of pyogenic granuloma or hemangioma. Histopathologically, we found an exophytic nodule bordered by epidermal collarette that showed lobular construction intervened by collagen bers with a mixture of slit-like vascular channels and small capillary-sized vessels. High-power view showed spindle cells and large atypical cells forming slit-like vascular spaces lled with red blood cells. Extravasation of red blood cells was observed. The tumor cells were positive for HHV-8, CD31, and CD34, leading to the diagnosis of pyogenic granuloma-like Kaposi’s sarcoma. Pyogenic granuloma-like Kaposi’s sarcoma is a rare variant of Kaposi’s sarcoma that also affects non-HIV-positive individuals. It appears commonly on the hands and feet and mimics pyogenic granuloma both clinically and histopathologically, carrying a risk of misdiagnosis. It is necessary to list this disease in the differential diagnosis for pyogenic granuloma-like lesions that occur on the limbs. Skin Research, 22 : 192-197, 2023

A 55-year-old man developed asymptomatic papules on his trunk and extremities about 1 year before. As the papules gradually increased, he visited his local doctor who referred him to our department for intensive examination and treatment. He had multiple and scattered brown papules about the size of a grain of rice on the bilateral elbow fossa, knee fossa, groin intertriginous area, and back. There was no exanthema on the genitals. Histopathological ndings showed irregular thickening of the epidermis with marked hyperkeratosis and granular degeneration. We diagnosed disseminated epidermolytic acanthoma mainly in the intertriginous areas. We suggest physical chronic stimulation triggered the onset of this disease. Skin Research, 22 : 198-201, 2023

A 76-year-old male had a gradually expanding blackish brown nodule on his back from half a year before presentation. As the previous doctor suspected malignant melanoma, he was referred to our hospital. Histopathological examination of excisional biopsy led to a diagnosis of malignant melanoma. Preoperative radioisotope examination showed left axillary nodal drainage and faint uptake of radioactive colloid in the lateral side of left scapula. Fluorescent lymphography revealed lymphatic ow to the left scapula, and blue-stained lymph nodes were found in the lateral side of left scapula. We resected the left axillary nodes and scapula lymph nodes. The scapula lymph node was considered an interval node. Histology revealed the interval node had metastasis, but the axillary lymph node had no metastasis. After the 7th dose of nivolumab as adjuvant therapy,metastasis to lymph nodes in the left axilla was found. Left axillary lymph node dissection was performed, and 2 out of 17 lymph nodes contained metastatic disease. An interval node is a lymph node that lies along the course of a lymphatic vessel between a regional lymph node. Interval nodes contain metastatic disease at nearly the same frequency as sentinel lymph nodes in regional lymph nodes. It is necessary to recognize interval nodes, and when metastasis is suspected, identify and remove them. Skin Research, 22 : 202-207, 2023

A 72-year-old male presented with a mass from the left side of the scrotum to the perineum since about a year before. The lesion was a large, easily hemorrhagic mass with ulceration. Erythema and depigmentation with unclear borders were observed. He was diagnosed with extramammary Paget’s disease (EMPD) by skin biopsy, and inguinal lymph node metastasis was conrmed by needle biopsy. Whole-body examination revealed prostate cancer, multiple lymph node metastases,and metastatic tumors in the lungs, liver, and bones. Both EMPD and prostate cancer were at an advanced stage, and it was unclear which tumor was the primary source of the distant metastasis. Hormone therapy for prostate cancer was selected as systemic treatment, and we started radiotherapy to the genital EMPD. Prostate-specic antigen decreased and the genital mass reduced signicantly, but liver metastasis worsened and the patient died 7 months after the rst visit. As a result, the distant metastasis was thought to have been caused by EMPD. In our case, two advanced cancers coexisted, making it difcult to determine the treatment strategy. Recently, it has been reported that androgens and their receptors are involved in the onset and proliferation of EMPD. Cases of EMPD complicated by prostate cancer have been reported occasionally. There may be an association between the onset mechanism and treatment. More cases need to be accumulated. Skin Research, 22 : 208-216, 2023

A 71-year-old woman with a history of ovarian cancer presented to her previous doctor with an mass on her left thigh that had been increasing in size for the past three years. She was suspected of having sebaceous carcinoma on skin biopsy and was referred to our department. A red mass on the left thigh was excised and diagnosed as sebaceous carcinoma. One month later, a red mass on the right upper arm was excised and diagnosed as sebaceous adenoma. Immunohistochemical staining showed no expression of MSH2 and MSH6 in tumor cells, which led to suspicion of Muir-Torre syndrome. She was referred to the Gastroenterology department, where colonoscopy revealed cancer of the cecum and transverse colon. When multiple sebaceous tumors and their characteristic histopathological ndings are observed, screening for DNA mismatch repair protein deciency by immunohistochemical staining is necessary to diagnose Muir-Torre syndrome and detect concomitant malignant tumors in their early stages. Skin Research, 22 : 217-223, 2023

A 71-year-old male patient developed a primary follicular lymphoma of the left eye and underwent rituximab ＋ bendamustine combination therapy 4years earlier. One month earlier, he developed pruritic, inltrated erythematous plaques on his head and back and had been taking bendamustine therapy. We diagnosed acute prurigo and started treatment with topical corticosteroids and oral 2nd generation antihistamines. After 3 months, the patient experienced itchiness followed by the development of erythematous plaques mainly on his face, which resolved in about a week. These symptoms kept occurring and resolving repeatedly. After 1 year and 10 months, the symptoms became prominent. A skin biopsy was performed to differentiate from other conditions such as skin inltration of lymphoma. Histopathologically, prominent inltration of lymphocytes from the dermis to the subcutaneous tissue was observed. In addition, less prominent inltration of degranulated eosinophils was also seen. However, there was no denite ame gure. Based on these ndings and clinical signs, the patient was diagnosed with eosinophilic dermatosis of hematologic malignancy. The rashes improved immediately after completing each course of obinutuzumab ＋ bendamustine (GB) therapy, including methylprednisolone sodium succinate 40 mg for follicular lymphoma, dexamethasone 2 mg, and obinutuzumab therapy. However, we temporarily discontinued GB therapy due to follicular lymphoma remission and new lesions appeared on his lower extremities. A combination of corticosteroids with follicular lymphoma treatment effectively improved skin rashes. Skin Research, 22 : 224-230, 2023

A 25-year-old male had atopic dermatitis since childhood. One month before his rst visit to our institution, he noticed erythema on his face and extremities, and had difculty lifting objects. On presentation, his face and neck were diffusely erythematous ; the trunk was spared, but linear erythema, known as scratch dermatitis, was observed on both upper arms. Erythema with scaling was also observed on the MP joints of the ngers, accompanied by petechial hemorrhage in the posterior nail cage. Blood test, skin biopsy, muscle biopsy, and electromyography revealed antiTIF1-γ antibody-positive dermatomyositis. A systemic examination for malignancy revealed advanced gastric cancer adjacent to the pancreas and lymph node, which had metastasized to the hepatic hilar region. Total gastrectomy, cholecystectomy, and pancreatoduodenectomy were performed for treating advanced gastric cancer. One month after surgery, multiple liver metastases within the S3, S5, and S6 regions were found by computed tomography with mild elevation of antiTIF1-γ antibodies. Chemotherapy was initiated two months after surgery. By this time, the patient was able to raise his upper arm to his head, and his skin rash had gradually improved. Chemotherapy was discontinued during the fourth course as the patient developed enteritis. A partial hepatectomy was performed 6 months after the rst surgery as a radical cure of gastric cancer. Thereafter, anti-TIF1-γ antibody test was negative, and there was no recurrence of skin rash or malignancy. Dermatomyositis positive for the anti-TIF1-γ antibody is often associated with malignant tumors, and treatment of malignant tumors improves dermatomyositis. The incidence of gastric cancer increases in patients in their 40s, but it is extremely rare in patients in their 20s. Comprehensive cancer workup for anti-TIF-1-γ antibody-positive dermatomyositis should be performed for patients in their 20s. Skin Research, 22 : 231-236, 2023

A 50-year-old man who was engaged as a gardener visited his local doctor with fever for 6 days prior to the initial visit, and skin rash without subjective symptoms on his extremities and trunk for 4 days prior to the initial visit. He was referred to our department. At the initial visit, erythematous macules of about 5 mm in diameter were scattered on the extremities and trunk, and a crust was observed on the left ankle joint. Blood tests showed increased leukocytes and elevated CRP, but normal liver enzymes and mild renal impairment with creatinine 2.27 mg/dl. PCR test from the crust was negative, but PCR test of whole blood detected the gene for Rickettsia japonica. A diagnosis of Japanese spotted fever was made. Histopathological ndings of the erythematous macule on the left lower leg showed leukocytoclastic vasculitis. Symptoms and laboratory ndings improved gradually after uid replacement and administration of minocycline. Japanese spotted fever is a tick-borne rickettsial infection characterized by fever, rash, and tick bite eschar. Laboratory tests often show elevated liver enzymes, but no renal impairment except in severe cases with multiple organ failure. Our case was a relatively rare case of Japanese spotted fever as it showed normal liver function and mild renal impairment, suggesting that the renal impairment was caused by microangiopathy associated with rickettsial infection. Based on the patient’s history, it was presumed that he was infected in the garden of a private house in the Rokko mountains in the Hanshin area. It is important to suspect this disease and provide early examination and treatment when a patient who has spent time in this area has a rash with fever, even if the patient has no history of activities in mountainous areas. Skin Research, 22 : 237-242, 2023