Anatomically pituitary tumors are classified by their size based on radiological findings; either microadenomas (less than <10 mm) or macroadenomas (equal or greater than ≥10 mm).Classification based on radioanatomical findings places adenomas into 1 of 4 grades (I–IV):Stage I: microadenomas (<1 cm) without sella expansion.Stage II:  macroadenomas (≥1 cm) and may extend above the sella.Stage III:  macroadenomas with enlargement and invasion of the floor or suprasellar extension.Stage IV: destruction of the sella.Histological classification utilizes an immunohistological characterization of the tumors in terms of their hormone production. Historically they were classed as either basophilic, acidophilic, or chromophobic on the basis of whether or not they took up the tinctorial stains hematoxylin and eosin. This classification has fallen into disuse, in favor of a classification based on what type of hormone is secreted by the tumor. Approximately 20–25% of adenomas do not secrete any readily identifiable active hormones (non-functioning tumors) yet they are still sometimes referred to as chromophobic. Functional classification is based upon the tumors endocrine activity as determined by serum hormone levels and pituitary tissue cellular hormone secretion detected via immunohistochemical staining. The "Percentage of hormone production cases" values are the fractions of adenomas producing each related hormone of each tumor type as compared to all cases of pituitary tumors, and does not directly correlate to the percentages of each tumor type because of smaller or greater incidences of absence of secretion of the expected hormone.
Iran also approved its own version of the monoclonal antibody in January 2016, as AryoTrust, and announced its readiness to export the drug to other countries in the Middle-East and Central Asia when trade sanctions were lifted.In 2016, the investigational biosimilar MYL-1401O has shown comparable efficacy and safety to the Herceptin branded trastuzumab.Trastuzumab-dkst (Ogivri, Mylan GmbH) was approved in the United States in December 2017, to "treat patients with breast cancer or gastric or gastroesophageal junction adenocarcinoma whose tumors overexpress the HER-2 gene." Ogivri was approved for medical use in the European Union in December 2018.In November 2017, the European Commission approved Ontruzant, a biosimilar-trastuzumab from Samsung Bioepis Co., Ltd, for the treatment of early breast cancer, metastatic breast cancer and metastatic gastric cancer. Ontruzant is the first trastuzumab biosimilar to receive regulatory approval in Europe.Herzuma was approved for medical use in the European Union in February 2018. Herzuma, a trastuzumab biosimilar, was approved in the United States in December 2018. The approval was based on comparisons of extensive structural and functional product characterization, animal data, human pharmacokinetic, clinical immunogenicity, and other clinical data demonstrating that Herzuma is biosimilar to US Herceptin.