CLINICAL CASE OF KERATOACANTHOMA
Authors: Voloshynovych M.S. , Boichuk T.R. , Holotiuk V.V. , Matkovska N.R. , Tkach V.Ye. , Chmut V.H. 
Published: March 2024

Keratoacanthoma is a common, rapidly growing skin tumour that has long been considered benign due to its staged course and ability to spontaneously regress. However, according to the latest World Health Organization classification, keratoacanthoma is classified as a well-differentiated form of squamous cell carcinoma.
Despite its long history keratoacanthoma remains a subject of controversy with regard to epidemiology, diagnosis, prognosis, and treatment.
The etiology and pathogenesis of keratoacanthoma are also not clearly defined. However, a number of factors have been identified that are highly likely to lead to the development of a tumour. In particular, these are ultraviolet and X-ray radiation, thermal and traumatic injuries, chemical carcinogens, genetic and immunological predictors, human papillomaviruses and certain drugs (sorafenib, infliximab, etc.).
Clinically, keratoacanthoma appears on the skin as a single or multiple crater-like nodule. Dermoscopy can be used for early diagnosis and differentiation from other tumour formations. The choice of therapy varies widely and depends on the location, stage of development, and size of the tumour.
The publication presents a number of cases which demonstrate the clinical, dermoscopic, and histological picture of keratoacanthomas.
Case presentation. Patient A, 44 years old, skin with signs of photodamage. A single dense nodule, up to 0.5 cm in diameter, on the anterior surface of the right lower leg. It appeared and grew rapidly over the past month.
Dermoscopy with photographic fixation was performed. A non-pigmented dome-shaped lesion with central yellow-brown keratinous masses, sporadic haemorrhages, and white structureless areas was observed. The vascular pattern was represented by looped, glomerular and helical vessels in a radial arrangement. The lesion was surgically excised. A pathohistological study was carried out. The conclusion was a well-differentiated squamous cell carcinoma of the skin.
In typical cases, the diagnosis of keratoacanthoma is not difficult. However, the combination with other skin lesions can distort the clinical picture. For example, in Patient B, keratoacanthoma developed against the background of seborrheic keratosis. In such cases, the use of dermoscopy can provide additional clues to the diagnosis and, accordingly, influence treatment methods.
Considering keratoacanthoma as a well-differentiated squamous cell carcinoma, surgical excision is preferred. The metastatic potential of this tumour is not significant, but in high-risk areas such as the lip or ear, it can reach 30%. At the same time, surgery reduces the risk of local recurrence. Other approaches include electrodissection and curettage, cryodestruction, intratumoural administration of methotrexate, 5-fluorouracil, bleomycin, and photodynamic therapy. These methods are appropriate in cases where the size or location of the tumour do not allow achieving the desired aesthetic effect.
Conclusions: 1. Keratoacanthoma is a well-differentiated squamous cell carcinoma with a low potential for metastasis. 2. Central yellow-brown keratinous masses, sporadic haemorrhages, white structureless areas, in combination with looped and glomerular vessels in radial disposition seen during dermoscopy of a nodule, may be a sign of keratoacanthoma. 3. The choice of treatment method for keratoacanthoma depends on its location and size; surgical excision of the tumour should be preferred.