An epidermoid cyst with atypical keratinocytes in the lowermost portion of the cyst wall.

We report on a 31-year-old Japanese female with an epidermoid cyst developed in the right inguinal region. The lesion was excised and drained by a surgeon. Since there was a local recurrence of the lesion within 2 months, the patient visited us, and the lesion was completely excised. Only the cells in the lowermost layer of the cyst wall showed dysplasia, which was characterized by irregular, and hyperchromatic nuclei with coarsely clumped nuclear chromatin pattern. However, solar elastosis was not observed, and spongiosis surrounding the atypical cells was present. In addition, melanophages were seen in the upper dermis. In conclusion, atypical keratinocytes in the lowermost portion of the cyst wall were deemed to be secondary to inflammation due to treatment by a surgeon rather than to development of both in situ and invasive squamous cell carcinomas in an epidermoid cyst.

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