Proliferating Trichilemmal Cyst of the Scalp: 9 Cases and Literature Review

Background: Proliferating trichilemmal cyst (PTC) is a rare adnexal tumor, primarily sitting on the scalp of elderly women. Its evolution is generally benign despite the rare malignant cases described. We report a series of 9 cases of which one is malignant and metastatic. Material and methods: We retrospectively reviewed data of all patients with PTC seen at department of dermatology in the Meknes military hospital, between January 2013 and December 2017. Results: 9 cases of PTC were diagnosed, which 8 in elderly women, with 62 years mean age. Trauma was found in one third of cases correlated with rapid growth of the tumor. The latter was symptomatic in 2/3 of the cases. Ulceration involved only the malignant case. The size varied from 1,5 to 12 cm. Recurrence after surgery was noted in 2 cases (malignant tumor and multi-cystic tumor). Discussion: PTC appears to have a well-distinguished profile of the simple trichilemmal cyst. Some clinical and histological features may constitute prognostic factors of aggressiveness. Histological and immunohistochemical study is crucial in the management. A large excision remains the only guarantee of complete remission without recurrence or metastasis. Conclusion: PTC remains misdiagnosed and very few series are reported. Prospective studies would allow the identification of prognostic factors of malignancy as well as better management.