Abstract: 【Abstract】 Objective To summarize clinical features of Kaposi′s sarcoma with a single skin lesion as the initial manifestation, and to analyze causes of its misdiagnosis. Methods Data were retrospectively collected from 12 patients with Kaposi′s sarcoma with a single skin lesion as the initial manifestation in the People′s Hospital of Xinjiang Uygur Autonomous Region from January 2020 to January 2022. Clinical and histopathological features and causes of misdiagnosis were analyzed. Results Among the 12 patients, 10 were males and 2 were females; 9 were of Uyghur nationality, and 3 were of Kazakh nationality; their ages ranged from 20 to 76 years, and 10 patients were aged ≥ 60 years. Skin lesions were mostly located on the feet （8 cases）, including the lateral edge of the foot （3 cases）, the sole of the foot （2 cases）, the ankle （1 case）, the dorsal side of the third toe （1 case）, and the interdigital regions between the third and fourth toes （1 case）; skin lesions were also observed on the fibular side of the right lower limb （2 cases）, on the right side of the dorsal tongue （1 case）, and on the dorsal side of the right little finger （1 case）. The skin lesions manifested as purple-red nodules in 9 cases, dark-red nodules in 2 cases, and purple-red plaques in 1 case, with maximum diameters of 0.5 - 3.0 （1.9 ± 0.83） cm. Skin lesions were accompanied by pain in 6 cases and by pruritus in 1 case. Histopathologically, skin lesions manifested as the proliferation of vascular endothelial cells, which could form obvious vascular cavity, or presented as a large number of proliferative spindle cells depending on the degree of tumor differentiation; immunohistochemical study showed that all the 12 patients were positive for human herpes virus 8; immunohistochemical staining of CD34 and CD31 was performed in 11 and 4 patients respectively, all the 11 patients were positive for CD34, and all the 4 patients were positive for CD31. Among the 11 patients presenting with nodules, 6 were initially misdiagnosed with skin infection, 2 with hemangioma, 2 with cutaneous squamous cell carcinoma, and 1 with dermatofibroma; the 1 patient presenting with plaques was initially misdiagnosed with psoriasis; 8 patients were first diagnosed in the department of dermatology, 3 in the department of burns, and 1 was first diagnosed in the department of maxillofacial surgery. Conclusion The Kaposi′s sarcoma initially manifesting as a single skin lesion was more common in males aged over 60 years, usually occurred on the feet, especially on the lateral edge of the foot, and mainly manifested as purple-red nodules; half of the patients were accompanied by pain; it was frequently misdiagnosed as skin infection in clinical practice, but histopathological examination could be helpful for its differential diagnosis.

Key words: Sarcoma, Kaposi, Skin manifestations, Diagnostic errors, Herpesvirus 8, human, Single lesion