Current pathological classification of pituitary adenomas

Immunohistochemical Markers of Soft Tissue Tumors: Pathologic Diagnosis, Genetic Contributions, and Therapeutic Options

After ~30 years of widespread usage, immunohistochemistry (IHC) has become a standard method of diagnosis for surgical pathology. Because of the plethora of diagnoses and often subtle nature of diagnostic criteria, IHC finds particular utility in soft tissue tumors. The use of progressively small amounts of tissue for diagnosis highlights the importance of this method. The sensitivity and crispness of IHC stains have progressively improved with the advent of new techniques. Traditionally, IHC detects cell-typic markers that characterize cell phenotypes, such as chromogranin for neuroectodermal tissue, myogenin for skeletal muscle, and cytokeratin for epithelium. However, the advent of genetic discoveries have led to IHC testing for detection of fusion gene products or overexpressed oncogenes associated with deletions and mutations. Proliferation-based markers such as Ki-67 can also be used for prognosis and grading, but more standardization is needed. Development of monoclonal antibody-based pharmaceuticals, such as imatinib or crizotinib, holds the promise of tailored anticancer therapy. IHC thus has assumed importance not only for diagnosis but also for guidance of personalized medicine.

Classification of pituitary adenomas

This brief review summarizes various schemes which were introduced to classify pituitary tumors of adenohypophysial origin. Many different classifications were proposed. Pathologists prefer classifications based on the morphologic features of tumor cells. The gold standard is the light microscopic study of hematoxylin-eosin stained sections of formalin fixed and paraffin-embedded tissues. For correlation between hormone production, secretory activity and cytogenesis, immunohistochemical and transmission electron microscopic investigation is needed. We are convinced that in the future, molecular and genetic techniques will also be applied. We present here our five-tier scheme for classification of pituitary tumors which was accepted by the 'World Health Organization International Histological Classification of Tumours'. This classification takes into consideration the clinical and laboratory findings, imaging results, histologic, immunocytochemical and ultrastructural features of tumor cells. Despite several recent attempts to assess the growth rate, aggressiveness and invasiveness of pituitary tumors, more work is required to draw conclusions on their prognosis.