An important aspect of the treatment of patients with gastric cancer (GC) is the accurate determination of human epidermal growth factor receptor 2 (HER2) status. HER2-positive cancer of the stomach and gastroesophageal junction is an aggressive molecular subtype of the tumor, detected in 5–20% of cases of adenocarcinoma of this localization.

Some problems may arise from incorrect or inaccurate methods of tumor biopsy and formalin fixation, which can be identified as one of the key factors that affect the reliability of HER2 assessment.

This article will cover the following aspects:

1) biopsy of histological tissue during endoscopic examination, taking into account localization;

2) the algorithm by which histological tissue is routed in the institution;

3) key points when analyzing the timing of fixation of histological tissue;

4) understanding and assessing the significance of HER2 expression in GC biopsies.

Photodynamic therapy (PDT) is a modern non-invasive technique of antitumor treatment. In its basis local or systemic application light-sensitive compound-photosensitizer (FS), which is selectively nakuplen in pathological tissue. In the interaction with the light of a certain length of the wave in the presence of oxygen in the fabric of the triggered photochemical process, driving to the gibel cell and activation of the immune response. Accumulation of FS in the affected tissues and targeted light allows to achieve high selectivity of action and minimal damage to surrounding tissues. Absence of resistance to PDT and possibility of combination with traditional methods of tumor treatment (surgical, radiation, systemic antitumor therapy) increase efficiency of PDT use in treatment of malignant neoplasms of different localizations, including palliative care.

The basis of current oncology is the verification of the disease. Only after the pathomorphological establishment of a clinical diagnosis, the treatment tactics of a particular patient are collectively selected. Now, in most cases, only pathomorphological diagnostics is not enough, it is necessary to conduct immunohistochemical and even molecular genetic researches, some of which are possible only in large federal referral centers. However, despite the existence of wide possibilities and detailed pathohistological classifications of neoplasms, with the development of modern diagnostic technologies, the medical community began to understand that some pathological processes go beyond the developed methods of diagnosis and cannot be verified within existing classifications. This way, patients with unclassifiable tumors currently do not have the opportunity to receive antitumor treatment based on evidence-based medicine, due to the lack of large-scale researches and clinical recommendations for the treatment of these types of tumors. The main purpose of the article is to once again draw the attention of the oncological community to the existence of unclassifiable tumors, in order to continue collecting information and jointly develop tactics for the diagnosis and treatment of these rare tumors.

Pheochromocytomas (PH) are rare catecholamine-secreting neuroendocrine tumors, which are hereditary in almost 40% of cases. Symptoms of pheochromocytoma are caused by excessive production of catecholamines or mass effect. The frequency of metastasis of PH can reach 25%. Patients with pheochromocytoma have a 4-fold higher risk of developing other malignant neoplasms (in men, liver cancer, biliary tract cancer, and central nervous system tumors are mainly diagnosed).

This article discusses a case of primary multiple change pheochromocytoma and gastric cancer. The main objective of the article is to increase clinical alertness and relevance of the problems of differential diagnosis and treatment in the progression of pheochromocytoma after a long relapse-free period.

Immune checkpoint inhibitors (ICIs), including cytotoxic T-lymphocyte associated antigen 4 (CTLA-4) and programmed death protein 1 (PD-1) or its ligand (PD-L1), are a new generation of immuno-oncological drugs that to date have demonstrated efficacy in a number of malignancies. The mechanism of ICIs action consist in the potentiation of the immune response by eliminating the tumor cells inhibitory effect on the T-lymphocytes activation. However, excessive immune system activation can cause the development of a special class of immune-related adverse events (irAEs) involved a wide variety of organs and systems, including the kidneys. Despite the fact that immunomediated kidney injury caused by ICI therapy develops quite rarely (2–15%), it can be serious and determine the patient’s prognosis, which necessitates early diagnosis and timely start of treatment. In this regard, awareness of the manifestations of ICI-associated renal irAEs is particularly relevant not only for oncologists and for nephrologists, but for doctors of other specialties.

Breast cancer, along with its high incidence, is characterized by an extreme degree of tumor heterogeneity, which is reflected in the presence of molecular genetic classification and treatment algorithms based on immunohistochemical and mutational characteristics of the tumor. The revolution in the treatment of the HER2-positive subtype occurred about 25 years ago, when the first targeted drug trastuzumab came to clinical practice. Currently, there are a large number of treatment options for this subtype of breast cancer, including the most advanced drugs such as monoclonal antibody + cytotoxic agent conjugates. Trastuzumab deruxtecan is a new generation antibody–drug conjugate that has been registered in Russia and other countries as the therapy of choice in 2 and subsequent treatment lines for metastatic HER2-positive breast cancer. The article presents randomized clinical trials that formed the basis of these indications, and a phase IIIb/IV study DESTINY-Breast12 demonstrating high intracranial activity of this drug. The clinical case illustrates the effectiveness of trastuzumab deruxtecan in a late line in a pretreated patient with multiple metastasis including brain, as well as the possibility of diagnosing and correcting a specific adverse event such as interstitial lung disease.

Immune checkpoint inhibitor-associated myositis is an extremely rare adverse event. However, the high level of mortality, the possible combination with other fatal complications, myocarditis, and myasthenia gravis, serve as motivation for the active detection and treatment of myositis. The management of the patient should involve a neurologist and a rheumatologist. In most cases, the administration of glucocorticoids is effective. Nevertheless, there is currently insufficient data on the pathogenesis of myositis and the treatment algorithms for steroid-refractory variants. A clinical case of the development of inclusion-body myositis in a patient receiving combined immunotherapy with antiCTLA4 and anti-PD-1 agents is presented.