Abstract: According to the characteristics of fatal disease of hyperplasia of skin and scabby among commercial layer chickens occurring in Shangdong province recently, epidemiological investigation, anatomic pathological change and observation, and histological and immunohistochemical examinations were carried out in suspected cases. The results showed that the disease was only discovered in the Hyline layer chickens of some batches of some chicken factory, about 1%-10% incidence，occurring among 5-day chickens, sustaining one month or so, finally leading to death. Yellow nodules could be seen initially throughout the skin, followed by the coalesced nodules, manking pachyderma and scab; histological examination indicated that the abnormal trichogenic tumor cells was invading the whole thickness of the dermis including nerve and striated muscle, and it was generally surrounded by fibrous tissue as well; Epidermal cells of skin lesions had a significant hyperplasia, and hyperplastic basal cell was atypia to some extent. Immunohistochemical examination revealed that in most of the tumor cells, CK was positive; Vimentin, CKLMW, CKHMW, P53, Ki-67 were negative; the hyperplastic connective tissue in the dermis were masculine for α-SMA. It could be concluded that the disease might be diagnosed as trichogenic epithelioma.