Keratoacanthoma may be easily mistaken with squamous cell carcinoma, both clinically as well as histopathologically. However, only keratoacanthoma can regress spontaneously.We report a case of a patient with a exophytic, ulceraded, infiltrated lesion in their scalp that was initially diagnosed as a keratoacanthoma. The histopathologic examination confirmed the presence of squamous cell carcinoma, and the tomography of the skull showed that the cancer had spread within the cranium. A surgical excision with wide margins and rotation flap was conducted, followed by adjuvant chemotherapy and radiotherapy treatments.There are a great number of accounts of squamous cell carcinoma erroneously diagnosed as keratoacanthomas in the specialist literature, illustrating the difficulty in differentiating between them.While there is no established effective method to distinguish between the two conditions, surgical excision should be the treatment of choice.

Keywords: CARCINOMA, SQUAMOUS CELL, KERATOACANTHOMA, SURGERY

The keratoacanthoma is a fast growing benign skin tumor that is composed of squamous cells and has clinical and histopathological features similar to those of the squamous cell carcinoma, and may undergo spontaneous regression without any treatment. It mainly affects elderly and immunosuppressed males who have fair skin, occuring in body sites that have been chronically exposed to sunlight, such as the face, forearms and backs of hands. The differential diagnosis with squamous cell carcinoma is particularly important. The recommended treatment is its surgical excision. Other treatment modalities, such as cryotherapy, electrocoagulation and intralesional injection of chemotherapeutic agents, are also available.

Keywords: KERATOACANTHOMA; LASER THERAPY; SKIN.

Keratoacanthoma is a malignant tumor that is rarely located in the subungual region, but which has a tendency to recur. Spontaneous regression of these lesions in the nail apparatus region almost never occurs, and a differential diagnosis with other neoplasias, particularly squamous cell carcinoma, is essential. The authors present the case of a man with a diagnosis of subungual keratoacanthoma, which responded well to surgical treatment and had a favorable development.

Keywords: NAILS; KERATOACANTHOMA; FINGER FALANGES.

O queratoacantoma (QA), apesar de frequente na prática diária, é um tumor que gera questionamentos. O aspecto mais intrigante associa-se à sua posição no limite entre malignidade e benignidade. A abordagem do tumor, bem como sua classificação, é controversa. Na definição da conduta, é importante levar em conta o potencial de transformação para carcinoma espinocelular. Desse modo, a excisão cirúrgica é a terapia de escolha, sempre que possível. Algumas situações merecem atenção adicional, como a imunossupressão associada. Neste artigo, relatamos um caso de QA gigante em um paciente com síndrome da imunodeficiência adquirida tratado com cirurgia micrográfica de Mohs.

Keywords: Ceratoacantoma; Retalhos Cirúrgicos; Neoplasias Nasais; Neoplasias Cutâneas; Cirurgia de Mohs; Síndrome de Imunodeficiência Adquirida; HIV; Imunossupressão

We report a case of a 72-year-old man who underwent surgical excision of a keratoacanthoma centrifugum marginatum (KCM) located on the left forearm. It is an uncommon variant of keratoacanthoma, which can assume large dimensions (up to 20 cm) and does not tend to spontaneous regression. The lesion is usually single, with raised borders, and has progressive centrifugal growth associated with central healing and atrophy. Due to its rarity and lack of pathognomonic histopathological features, KCM can be a diagnostic challenge for dermatologists and pathologists.

Keywords: Keratoacanthoma; Neoplasms; Skin neoplasms