Abstract: 【Abstract】 Objective To analyze clinical and pathological features of 320 cases of Spitzoid tumors. Methods Clinical and pathological data were collected from 320 patients with Spitzoid tumors in Department of Dermatology, Xijing Hospital from January 2005 to January 2020, and retrospectively analyzed. Results The 320 patients included 141 males and 179 females, aged 0 - 65 （12.5 ± 11.7） years, and their course of disease ranged from 1 month to 30 years. Among them, there were 307 patients with Spitz nevi, 8 with atypical Spitz tumors and 5 with Spitzoid melanoma. Most skin lesions were solitary, and occurred on the head, face, trunk and limbs, with clear boundaries. Among the 307 patients with Spitz nevi, the skin lesions were mainly black （132 cases, 43.0%） and red （108 cases, 35.1%） in color, most of which were uniformly pigmented （262 cases, 85.3%） with smooth surfaces （272 cases, 88.6%）. There were several special clinical subtypes of Spitz nevi, including Spitz nevus arising in a nevus spilus （11 cases, 3.6%）, agminated Spitz nevus （11 cases, 3.6%）, disseminated Spitz nevus （6 cases, 2.0%）, nodular Spitz nevus （7 cases, 2.3%） and keloid?like Spitz nevus （1 case, 0.3%）. Characteristic histopathological manifestations of Spitz nevi included pagetoid spread of epidermal nevus cells （123 cases, 40.1%）, Kamino bodies at the dermo?epidermal junction （74 cases, 24.1%）, horizontal band?like distribution of nevus cells （177 cases, 57.8）, wedge?shaped distribution of nevus cells （118 cases, 38.4%）, fissures around nevus cell nests （177 cases, 57.8%）, physiological mitotic figures （117 cases, 38.1%）, and fine nuclear chromatin （307 cases, 100%）. According to the special histopathological manifestations, Spitz nevi were divided into pigmented epithelioid Spitz nevus （9 cases, 2.9%）, desmoplastic Spitz nevus （13 cases, 4.2%）, hemangiomatous Spitz nevus （8 cases, 2.6%）, verrucous Spitz nevus （12 cases, 3.9%）, mucoid Spitz nevus（10 cases, 3.3%）, halo?like Spitz nevus （4 cases, 1.3%）, etc. Among the 8 cases of atypical Spitz tumors, 4 skin lesions were black, 7 were uniformly pigmented, and 3 had rough surfaces; the characteristic pathological manifestations included mild to moderate atypia of cells, mitotic figures （2 - 6 cells/mm2 in 7 cases）, and coarse nuclear chromatin （5 cases）. Among the 5 cases of Spitzoid melanoma, 3 had red skin lesions, 4 were non?uniformly pigmented, and 3 had rough surfaces; the characteristic pathological manifestations included pagetoid spread of melanocytes （3 cases）, non?polar infiltrating growth of immature tumor cells, pathological mitotic figures （3 cases, > 6 cells/mm2）, coarse nuclear chromatin and obviously stained nuclear membrane. Conclusions Spitzoid tumors are characterized by unique clinical and histopathological features. There are various clinical and pathological subtypes of Spitz nevi, and atypical Spitz tumors have clinical and pathological characteristics of both Spitz nevi and melanoma.

Key words: Nevus, epithelioid and spindle cell, Spitzoid tumor, Spitz nevi, Atypical Spitz tumor, Spitzoid melanoma