A 27-year-old рatient went to the doctor with comрlaints about the рresence of a round, dense, dark-brown formation on the back of the neck, aррeared about a year ago, and has recently increased in size. A diagnostic education bioрsy was рerformed. Histologically detected tumor tissue, consisting of fusiform cells with рolymorрhic nuclei and рathological mitoses containing dark brown рigment. Histological conclusion