BACKGROUND

Seborrheic keratosis (SK) is one of the most common skin neoplasms diagnosed at dermatologist’s appointment. There are various types of SK, that in combination with the fact of frequent traumatization explain the great clinical variety and other neoplasms’ simulation including malignant ones.

OBJECTIVE

To identify clinical and dermoscopic features of atypical SK simulating malignant and benign skin neoplasms.

MATERIAL AND METHODS

The study was carried out at the Center of Diagnosis and Treatment of Skin Tumors of the PRMU University Clinic for the period from January 2018 to December 2022. A total of 3339 medical records of patients who have applied to the center with skin neoplasms were analyzed, 315 cases of SK diagnosis were revealed, in 70 cases clinical and pathomorphological mismatch of preliminary and final diagnosis was detected — atypical SK, 70 cases were included as a control group for comparative analysis — typical SK.

RESULTS

Atypical SK in comparison with typical statistically significantly appeared for less than one year, had an average diameter of 8 mm, asymmetry of 70% and polychromaticity of 44.3%. There were no dermoscopic typical features for atypical SK (p<0.05): boundaries sharpness (18.6%), multiple milium-like cysts (28.6%), comedone-like openings (17.1%), hairpin vessels (11.4%), «moth-eaten» edge (1.4%) and surface by type of brain convolution (12.9%).

At the same time, «atypical» signs were detected as well (p<0.05): pigment network (3.55%), globules (3.55%), unstructured area (29.11%), punctate and glomerular vessels (24.14%), crusts (11.36%). In addition, 4 dermoscopic SK patterns were described: pigment (31.43%), hyperkeratotic (27.14%), vascular (20%) and unstructured (21.43%).

CONCLUSION

Atypical SK is characterized by clinical asymmetry and polychromaticity, dermoscopic absence of «typical» SK picture, presence of pigment network, globules, unstructured area, glomerular and punctate vessels and crusts, is most commonly represented by pigment and hyperkeratotic dermoscopic patterns.