Carcinomas basocelulares do couro cabeludo após radioterapia por tinea capitis na infância: estudo clinicopatológico e genético. ; Basal cell carcinomas of the scalp post-radiotherapy for tinea capitis in childhood: clinicopathologic and genetic study.

Tese de Programa de Doutoramento em Ciências da Saúde apresentada à Faculdade de Medicina ; Background: Basal cell carcinoma (BCC), the most common form of skin cancer, is mostly associated with sun exposure. Low-dose X-ray radiotherapy to treat tinea capitis during childhood is also a well-known risk factor for scalp BCCs. Although there are several studies in the literature, post-radiotherapy BCCs have not been thoroughly characterized in their clinical, histopathological, immunohistochemical and genetic features. In addition, previous studies have not explored potential differences between BCCs associated with radiation therapy and BCCs related to exposure to ultraviolet (UV) radiation.Objectives: The general objective of our work was to characterize a series of patients with post-radiotherapy BCCs, following treatment for tinea capitis in childhood, and to compare them with patients diagnosed with BCCs from sun-exposed areas.Material and Methods: The clinicopathological and immunohistochemical evaluations were performed as an observational, retrospective study based on a population collected from the Dermatology Department of a University Hospital.The clinical study investigated features related to the patients and their tumors, including age at presentation, latency period between radiotherapy and diagnosis, number of lesions, recurrences, associated features and comorbidities. The histopathological characterization included the main subtypes of BCC, level of invasion, features of divergent differentiation, pigmentation and changes in the surrounding tissue. The immunohistochemical study was directed towards the features of follicular differentiation and included cases of post-radiotherapy BCCs (both conventional and infundibulocystic) and BCCs from sun-exposed areas, using the immunohistochemical markers PHLDA-1, CK15, CD34, β-catenin and calretinin. The genetic study involved prospective collection of tumour samples from post-radiotherapy BCCs and BCCs from sun-exposed areas. The samples were analysed ...