Differentiation towards cartilage and bone in a primary tumour of pleura. Further evidence in support of the concept of mesodermoma.

A case of primary pleural malignant tumour is reported and its histological features described including histogenetic factors. The histological pattern was predominantly and typically biphasic (both epithelial and sarcomatous) with foci of sarcomatous cartilaginous differentiation and osteoid formation reproducing an embryonal pattern of enchondral ossification. This provides supportive evidence for the use of the term 'mesodermoma' to identify primary tumours of serous membranes and to the concept of identification of mesothelium with embryonal mesoderm.