Abstract: 【Abstract】 Objective To analyze histopathological features of pityriasis rosea. Methods Clinical and pathological data were collected from 110 patients with pityriasis rosea in Department of Dermatology, Peking University First Hospital between January 2000 and May 2021, and analyzed retrospectively. Results Among the 110 patients, 59 were males and 51 were females; their ages ranged from 6 to 79 years, with a median age of 32 years. There were 105 cases of general type of pityriasis rosea, presenting as red papules and maculopapules, whose long axes were parallel to the dermatoglyphs, accompanied by collar-like desquamation distributed mainly on the trunk and proximal extremities; there were 5 cases of special types of pityriasis rosea, including 1 case of erythema multiforme, 3 cases of purpuric pityriasis rosea, and 1 case of vesicular pityriasis rosea. Histopathological examination showed focal parakeratosis in 85 cases （77.3%）, epidermal spongiosis in 107 cases （97.3%）, focal basal cell edema in 106 cases （96.4%）, superficial dermal perivascular inflammatory cell infiltration in 95 cases （86.4%）, and erythrocyte extravasation in 20 cases （18.2%）. Conclusion The relatively specific histopathological feature of pityriasis rosea was mild basal cell edema, and pityriasis rosea should be differentiated from interfacial dermatitis rather than spongiotic dermatitis.

Key words: Pityriasis rosea, Pathologic processes, Skin manifestations, Diagnosis, differential, Basal cell edema