Figure 13 (A) At low magnification, this desmoplastic malignant mesothelioma appears deceptively bland with features reminiscent of fibrous pleurisy. The invasion of chest wall adipose tissue by spindled tumour cells is seen at the bottom of the field. (B) Higher‐power view of (A) showing fascicular arrays of hyalinised collagen amid which mildly atypical spindle cells infiltrate fat. (C) Sarcomatoid region of a desmoplastic malignant mesothelioma showing diffuse invasion of chest wall skeletal muscle. (D) Desmoplastic malignant mesothelioma invading pulmonary parenchyma. In this example, tumour spreads into the lung as intra‐alveolar plugs in a peculiar bronchiolitis obliterans‐organising pneumonia‐like pattern. (E) Pan‐cytokeratin staining of the tumour in (A) highlights invading tumour cells within adipose tissue of the chest wall.