A 40-year-old woman presented with a 5-year history of a mass overlying her right pectoralis major muscle. Histopathology of the lesion revealed a florid granulomatous infiltrate including an atypical lymphocytic component with marked epidermotropism consistent with granulomatous mycosis fungoides. Staging investigations demonstrated the tumour to be localized to the right chest. Consequently, the patient was treated with radiotherapy (50 Gy) to the lesion with good clinical effect. However, she soon developed a clinically palpable lesion on the left chest outside the radiotherapy field. Positron emission tomography scanning demonstrated an extensive left-sided chest wall tumour and also residual tumour on the right. This left-sided lesion failed to respond to systemic chemotherapy. Further radiotherapy (50 Gy) has recently been administered to the left chest lesion; the response is being monitored. While granulomatous inflammation has been previously described in cutaneous T-cell lymphomas, it is rare and is often associated with a delay in the diagnosis and difficulty with clinical staging. The clinical presentation can be extremely variable and consequently, diagnosis rests with histological features, immunohistochemical studies and gene rearrangement analysis.