Abstract
We report a case of malignant mesothelioma who presented characteristic intracytoplasmic crystalloid inclusions composed of the whorled rough endoplasmic reticulum. A brief discussion on their diagnostic value is also given.
A 61-year-old man was admitted because of pleural effusion. The computed tomography demonstrated a mild right pleural thickening, but the diagnosis could not be made with any certainty by cytological examination of the effusion or biopsy of the pleura. The patient was followed in another hospital with thoracentesis, but was readmitted due to the gradual bulging of the chest wall around the thoracentesis. The pleural effusion was markedly viscous, and a diagnosis of malignant mesothelioma was made by cytological and biopsy examinations.
The cytological study performed on the first admission revealed numerous mesothelial cells with papillary structure but no significant atypism. Most of the cells contained intracytoplasmic crystalloid inclusions. Ultrastructurally, the inclusions were made up of concentric lamellar rough endoplasmic reticulum. Fibrils with 12.2 nm periodical cross-striation were present in the cisternae of the reticulum. Such crystalloid inclusions were also observed in the mesothelioma cells on the second admission. As the significance of such inclusions is not clear, further study is necessary to determine whether or not they have diagnostic significance.
