Skin tumors that are easily misdiagnosed as “malignant”. We can easily determine “malignancy” when one or more of these features are present in the clinical examination: pigmentary changes, chronic infection, repeated breakage or exudation, repeated scaling or crusting, shallow ulcers, crater-like, cauliflower-like, rapid enlargement, and satellite nevus-like manifestations around the skin. 1, seborrheic keratosis with infection Clinically common, as a pre-malignant skin tumor damage, should be excised and treated, intraoperative cryopathology to diagnose. 2. Keratoacanthoma I have seen only solitary ones, which are more common than other types, but also multiple, eruptive and borderline eccentric ones. Solitary ones typically appear nodular and crater-like, often with a reddish margin, and can grow rapidly within a few months. The appearance is extremely similar to that of squamous carcinoma, and even though similar in pathology, it can still be differentiated with enough experience. If there is one feature that can provide differentiation when pathology is not done, I think it is the course of the disease. Although the textbook mentions that it can heal spontaneously, none of the patients I have come in contact with have received enough follow-up to determine this feature, because those who have come in have already been excised because they need a definitive diagnosis. 3. Epithelioma of the hair Single hair resembles basal cell carcinoma, and individual cannot be identified even by pathology, and the textbook indicates that it should be treated as basal carcinoma. 4. Solar keratosis Pre-cancerous lesions, often accompanied by atypical hyperplasia, are easily diagnosed as Bowen’s disease because they manifest as erythema and scaling in sun-exposed areas. 5. Bowen’s disease Because it is a carcinoma in situ, it has actually undergone malignant transformation, but for some reason, when handling chronic diseases, he is excluded. It is mentioned here because I want to emphasize the point that once it is found, attention needs to be paid to exclude the presence of other malignant tumors. 6. Pigmented nevus combined with epidermal cyst with infection Because pigmented nevus itself has sebaceous glands, hair follicles and other skin appendages, it is possible for epidermal cyst to occur, and when it is accompanied by chronic infection, it is easy to misdiagnose it as “malignant change”. 7, pigmented nevus, seborrheic keratosis and other skin tumors with viral warts on top of the original skin lesions appear human papillomavirus infection, the people say “wart”, but some less typical lesions, easy to highly suspect malignant change. 8. pigmented changes on the bottom of the foot or under the nail The cause is mostly inflammatory changes or subcutaneous petechiae caused by the rupture of tiny blood vessels after trauma, but because they appear as black patches, they are easily misdiagnosed as malignant black. I had a profound experience of a young male with a black spot on the heel and a history of nearly one year, which was highly suspected to be malignant black at the time of consultation and was excised. Ten days postoperatively, the cut edge was blackened centrally and skin necrosis appeared, considering poor blood flow to the plantar aspect of the foot and high tension. Delayed suture removal still did not change the outcome of incisional dehiscence. A lesson was learned: do not judge it as malignant easily, and you cannot take it for granted without sufficient evidence. In fact, if the patient pursues it, it is an overtreatment, the patient suffers and the individual’s career may be affected.