The pericardium includes the parietal and visceral pericardium. The parietal pericardium con-sists of the tough fibrocollagenous tissue sac covering the heart. Its inner surface is lined by mesothelial cells. Usually there are very few blood vessels coursing through it. The visceral pericardium is a more delicate, thinner fibrous layer covering the heart and epicardial fat. In general, the pericardial specimens submitted to surgical pathology are samples of the parietal pericardium, which can become very thick as a result of inflammatory and/or neoplastic infil-tration.
In addition to the overall dimension of the piece of tissue received, it is important to record the average thickness of the pericardial sample. Document the presence or absence of adipose tissue, areas of hemorrhage, nodules, and the status of the surface (e.g., smooth, shiny, ragged, fibrinous, granular). Note whether there are fibrin deposits, fibrous collagenous bands, cystic spaces, or papillary projections. Rarely, frank ab-scesses are demonstrated on gross examination.
Adequate sampling may vary according to the size of the specimen and the clinical information. Careful gross examination aids in determin-ing what should be sampled for histology. A thickened pericardial sample (i.e., pericardial thickness of more than 3 mm) should be fixed and cut perpendicular to the inner surface of the pericardial sac, which in most cases is easily iden-tified. Serial slices may be submitted to maximize the surface area. If the pericardial sample is thin (less than 2 mm in thickness) one should make sure that the sections are embedded “on edge” to perform an adequate histologic examination.