Keloid scars are benign dermal collagenous lesions that arise in the reticular layer of the dermis as a result of a period of prolonged wound healing due to injurious cutaneous insult. It is diagnosed clinically by a history of injury preceding its appearance and its pathognomonic encroachment beyond the boundary of the original wound. There are multiple factors that predispose an individual to keloid scar formation but no single hypothesis sufficiently explained its complex pathogenesis. The spontaneity of keloid scar to arise de novo without prior cutaneous injury is very rare. Although the non-specific appearance of spontaneous keloid scar can resemble various malignant or benign tumors, it is of paramount importance to accurately diagnose it due to the difficulty and complexity of keloid scar treatment or the atrocious outcome of its mismanagement. Here, we presented a rare case of spontaneous keloid scar over an unusual site of occurrence, and its disfiguring consequences as a result of misdiagnosis and treatment. We also highlighted the diagnostic challenge facing many clinicians when spontaneous keloid scar occurred in an individual without significant predisposing factors. Therefore, extra vigilance should be exercised in our practice and the spontaneity origin of keloid scar should be borne in one's mind.