CLINICAL CASE OF RECURRENT NEVUS
Authors: Voloshynovych M.S. , Holotiuk V.V. , Boichuk T.R. , Matkovska N.R. , Girnyk G.Ye. 
Published: July 2023

Abstract. Introduction. Recurrent nevus is a benign proliferation of melanocytes that occurs at the site of non-radical removal of a previously existing nevus. Recurrence rates range from 0.3% to 28% and most often occur within 6 weeks to 6 months after removal. Clinically recurrent nevus is characterized by uneven pigmentation with uneven edges in the area of the scar.
Walton et al. began researching the phenomenon of recurrent nevus in 1957. In 1975, Kornberg and Ackerman reported that a pigmented recurrent nevus can resemble superficially spreading melanoma both clinically and histologically, and proposed the term pseudomelanoma to describe this benign phenomenon. Currently, the term is rarely used, but it motivates a thorough examination of patients with such a problem.
Case presentation. Patient A. complained about the presence of a formation in the area of the outer surface of the right forearm, which has existed for many years, it was injured several times, but has recently changed the colour. On examination, a nodule up to 0.5 cm in size, heterogeneously pigmented, with peripheral erythema was found in the indicated place. During dermoscopy, chaotic unevenly distributed pigmentation, consisting of dots, globules, forming a cellular structure in a scattered manner is determined, zones of segmental radial lines are present as well. The vascular pattern in the central part of the formation is not defined, on the periphery it is represented by slightly noticeable point vessels. Digital post-processing using machine learning technology was carried out to improve visualization of blood supply. Multiple point, curved, and convoluted vessels with few branches around the formation, and several central vessels in the pigment cells are determined. Surgical removal of the tumor was performed with involvement of the erythema zone, taking into account the peculiarities of pigmentation and vascular pattern. The pathogistological structure is presented in the photomicrograph. The epidermis has a typical structure, with areas of slight acanthosis; hyperpigmentation of the basal layer is also observed. In the dermis, foci of brown pigment deposition, single lymphocytes, there are areas of intradermal lobular-horizontal fibrosis with angiomatosis and scattered lymphocytic infiltration. Taking into account the clinical data, there is a recurrence of a melanocytic nevus on the background of a skin scar (Recurrent neavus).
Teaching point. Dermoscopy allows obtaining additional data for the differential diagnosis of recurrent nevus and recurrent melanoma. A recurrent nevus is characterized by relative symmetry of formation and a pattern of segmental radial lines. The formation is limited to the area of the scar and does not go beyond it. Also, in the case of recurrent melanoma, a continuous growth in dynamics and a later appearance of recurrence from the moment of intervention will be obvious.
Conclusions. As clinical practice demonstrates, under certain circumstances, recurrent pigmentation can be observed in cases of nevi that have been traumatized. It will be visible both dermoscopically and pathohistologically. Sometimes it is difficult even for experts to distinguish between a highly irritated nevus and a melanoma.