Basal Cell Carcinoma Arising Within a Favre-Racouchot Syndrome Lesion: A Rare Case and Literature Review.

Concurrence of Favre-Racouchot syndrome (FRS), a chronic dermatosis, and skin cancer is rare. In this study, we present an exceptionally rare case of basal cell carcinoma (BCC) arising within a FRS lesion. An 84-year-old female farmer had a mass in the lower left limb for 30 years without medical treatment. Over the past year, especially in the month prior to this visit, the mass enlarged significantly. On examination, a well-defined, rounded mass measuring approximately 4 cm in diameter was noted on the anterior aspect of the left calf. The mass had a rough surface with papillary hyperplasia and a mild erythema at the base. Open and closed comedones were observed, but no cysts or yellowish nodules were present. Histopathological analysis showed degradation and reduction of elastic fibers in the lesion dermis, along with the presence of comedones and cysts. Furthermore, scattered basaloid cell nests of varying sizes were present in the dermis, with peripheral tumor cells arranged in a palisading pattern. Peritumoral clefts were observed and the cell nuclei were hyperchromatic and occupied most of the cell. BCC associated with FRS was diagnosed. The patient underwent complete surgical excision. No recurrence was observed over an 18-month follow-up period. In conclusion, concurrence of BCC and FRS is rare. Delayed diagnosis of this condition can lead to more invasive disease progression. To improve early detection for timely treatment, clinicians should maintain a high index of suspicion for malignant transformation in patients with longstanding FRS, particularly those presenting with rapidly evolving lesions.