Malignant transformation of an epidermoid cyst in the perineal region:a clinicopathological analysis of a case and review of literature

JIAN Can-hui; DING Chao-xia; LI Jing; WANG Jin-jing

doi:10.3969/j.issn.1007-8096.2024.10.007

Abstract：Objective To investigate the clinicopathological features,diagnostic criteria,and differential diagnosis of malignant transformation in epidermoid cysts(EC).Methods A retrospective analysis of the clinicopathological features,immunophenotype,diagnosis,and differential diagnosis of a pathologically confirmed case of malignant transformation in an epidermoid cyst was carried out,along with a review of relevant literature.Results The patient was a 68-year-old male who presented with a perineal mass that had been present for over 50 years.Clinically,the perineal mass was smooth,easily movable,and non-tender.The mass was completely excised surgically,and there has been no recurrence or metastasis to date.Pathological examination revealed irregular cystic tissue with localized spiculation on the cyst wall.Histologically,the cyst wall was lined by squamous epithelium,and the cyst cavity contained degenerated lamellar keratin.In the area of malignant transformation,squamous epithelium exhibited stromal invasion in a nest-like pattern.Pathological diagnosis confirmed the malignant transformation of the epidermoid cyst to a well-differentiated squamous cell carcinoma.Immunohistochemistry showed strongly positive expression of CK5/6,P40,and EMA in the tumor cells,with a Ki-67 proliferation index of 40%.Conclusion Malignant transformation of an epidermoid cyst is a rare skin tumor that can occur at any age,though it more commonly occurs in the elderly and typically arises in the head and neck region.Clinically,it usually presents as a long-term chronic condition with low invasiveness and generally has a good prognosis.Diagnosis is primarily based on morphological and immunophenotypic characteristics.It is important to differentiate it from other skin tumors.The main treatment approach is wide local excision,supplemented by radiotherapy and chemotherapy.Early diagnosis and treatment are crucial.