Cutaneous squamous cell carcinoma (SCC) is a common non-melanoma skin cancer (NMSC). Although most cutaneous SCC in people with lighter skin pigmentation as a result of sun damage, patients with underlying conditions such as skin ulcers and chronic inflammation-including conditions such as lupus vulgaris (LV) and chronic discoid lupus erythematosus-are also predisposed to developing SCC. Here we report a case of secondary SCC diagnosed in a 54-year-old patient with 20 years of lupus vulgaris without prior formal systemic treatment, a rarity in clinical practice. Two months ago, the patient developed papules on the right cheek that ulcerated and discharged purulent fluid. Laboratory tests revealed a positive TSPOT result and histopathological examination confirmed granulomatous lesions, supporting the diagnosis of SLE. However, a tissue biopsy unexpectedly revealed a moderately differentiated SCC of the keratinizing type. In this case, we performed surgical excision of the lesion followed by cosmetic closure and adjuvant photodynamic therapy (PDT). Concurrently, the patient underwent systemic anti-tuberculosis treatment. At 6 months posttreatment, no tumour recurrence was observed and the rash associated with lupus erythematosus had also resolved. The patient was satisfied with the treatment outcome.