Primary malignant tumors of the chest wall account for less than 1 % of all neoplasms, with chondrosarcoma constituting 20 % of these. Secondary chondrosarcomas developing against the background of pre-existing enchondromas or osteochondromas (both solitary and multiple, as seen in Ollier’s disease or Maffucci syndrome) are even rarer. The slow growth of such neoplasms often leads to late diagnosis, and the complex anatomy of the localization poses challenges for specialists, requiring thorough preparation and coordinated work of a multidisciplinary team. The available literature contains limited reports on the surgical treatment of chondrosarcoma of the sternoclavicular joint, the I–II ribs, and/or the sternum, with few observations documented.

 This article presents a literature review dedicated to this issue, as well as two rare clinical cases of patients  with chondrosarcoma of the upper thoracic aperture, which are of interest to oncologic orthopedists, thoracic  and vascular surgeons, as well as diagnosticians.

 Synovial sarcoma is characterized by a typical transcript SS18::SSX. However, despite a common pathogenesis  and similar therapeutic approaches, opposite responses to therapy are sometimes observed. Supposedly, this can be associated with additional and alternative pathways of genetic and epigenetic regulation.
 In this review, the problems of synovial sarcoma  diagnosis, pathogenesis and new therapy methods, including targeting epigenetics, are discussed.

Introduction. Giant cell tumor (GCT) of bone is a relatively rare neoplasm. Its malignant transformation in the form of sarcomatous changes occurs in 8–10 % of cases. The literature lacks data on radiological signs and differential diagnostic criteria of primary malignant GCT of bone. Clear guidelines on the density range of the affected area  for differential diagnosis are also absent.

 Aim. To analyze dynamics of tumor density changes in patients with malignant GCT of bone using computed tomography densitometry.

 Materials and methods. Ten patients (mean age 45.8 ± 4.2 years, range 28–58 years) with malignant GCT of bone were examined. All underwent treatment with denosumab with subsequent surgical intervention. Bone changes were assessed visually. Densitometric analysis was performed in accordance with a method developed by us involving determination of tumor density in Housefield units (HU) and relative tumor density index (k) (ratio between tumor density and density of the unaffected limb at the same level).

 Results. After 6 injections of denosumab, a clear sclerotic rim appeared at the tumor periphery containing thin lines of ossification. Analysis of densitometric parameters showed that tumor density after denosumab administration increased from 46.3 (median (Мe) 35.0; interquartile range (IQR) 51.4) HU to 88.8 (Мe 84.8; IQR 118.4) HU, while relative tumor density index increased from 0.33 (Me 0.22; IQR 0.45) to 0.68 (Me 0.62; IQR 0.89). Earlier we have published threshold values of these parameters (≥139.5 HU and ≥0.97, respectively) at which probability of residual tumor is lowered (sensitivity 81.8 %, specificity 96.6 %). Taking into account these values, 9 of 10 patients required continuation of therapy.

 Conclusion. Computed tomography densitometry allows to evaluate changes caused by denosumab therapy in patients with malignant GCT of bone. According to radiological data, progression of this disease has unique features. Taking into account histological types of malignant GCT, longer periods of observation and denosumab administration or changes in treatment tactics at the preoperative stage can be considered, as well as potential use of this drug in other primary bone tumors.

Introduction. Telangiectatic osteosarcoma is a rare histological subtype of osteosarcoma, accounting for 2–12 % of all cases. Although telangiectatic osteosarcoma is characterized by unique morphological and radiological features, its diagnosis might be challenging due to its similarity to aneurysmal bone cysts and giant cell tumors.

Aim. To evaluate oncologic outcomes in a large homogeneous series of children and adolescents with telangiectatic osteosarcoma.

 Materials and methods. The study included treatment-naive patients under the age of 18 with a diagnosis of telangiectatic osteosarcoma confirmed between January 1, 2012, and December 31, 2023, and prospectively registered at the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology. All patients received MAP-based chemotherapy (according to the EURAMOS-1 protocol). Treatment outcomes were assessed

using event-free survival and overall survival rates, calculated by the Kaplan–Meier method. Results. Among 368 primary osteosarcoma patients, the telangiectatic subtype was diagnosed in 40 cases (10.8 %). At initial diagnosis, 48.7 % of patients had pulmonary metastases, and pathological fractures were identified in 33.4 % of cases. Histological examination showed good response to preoperative chemotherapy in 76.3 % of patients. The median follow-up was 3.65 years. 5-year overall survival and event-free survival rates for all patients were 73.4 % and 57.3 %, respectively.

 Conclusion. Due to combination treatment including surgical tumor resection and neo- and adjuvant polychemotherapy, treatment outcomes for patients with telangiectatic osteosarcoma are similar to outcomes in patients with conventional osteosarcoma.

Introduction. Desmoid-type fibromatosis is a rare locally aggressive tumor originating in connective tissue and characterized by locally destructive invasive growth, high recurrence potential and absence of metastases. In recent years, attempts to standardize the treatment of this disease were made but all current therapy methods have disadvantages and do not guarantee absence of disease progression.

 Aim. To evaluate safety and efficacy of radiofrequency ablation in patients with desmoid tumors.

 Materials and methods. The study included 9 adult patients of both genders (4 men and 5 women) aged 21–65 years with morphologically verified diagnosis of desmoid tumor of the soft tissues with extra-abdominal location. All patients in the study group underwent control examination prior to the procedure. The treatment was performed in several stages at low volume (2–50 cm3) taking into account tumor size. Efficacy was determined using pain syndrome regression per the VAS and Watkins scale, as well as Karnofsky Performance Status Scale. Safety was evaluated per the Clavien–Dindo Scale.

 Results. Analysis of pain syndrome dynamics per the VAS and Watkins scale before and after treatment was performed. For both VAS (p = 0.004) and Watkins scale (p = 0.014), statistically significant changes were observed. Pain syndrome decreased to 50 %, and the percentage of patients declining analgesics increased to 66.7 %. Analysis of the performance status per the Karnofsky scale also showed statistically significant changes (p = 0.015). Mean value increased to 90 %. No complications were reported at the time of the study.

 Conclusion. Radiofrequency ablation showed itself to be a safe and effective method for treatment of desmoid tumors. However, further studies are necessary involving more patients.

Introduction. Cutaneous melanoma is a malignant tumor of neuroectodermal origin developing from melanocytes (pigment cells) of the skin. It is characterized by aggressive growth, high risk of metastasis and progression.

Aim. Retrospective study of outcomes of surgical treatment of cutaneous melanoma with biopsy of the sentinel lymph node and subsequent intervention on regional lymph nodes/observation and evaluation of risk factors of disease progression.

 Materials and methods. Retrospective cohort study was performed at the Nizhny Novgorod Regional Clinical Oncological Dispensary. The study included patients with cutaneous melanoma who underwent surgical treatment with biopsy of the sentinel lymph node.

 Results. Risk factors for disease progression were analyzed, and the unfavorable prognostic value of the thickness  and presence of ulceration of the primary tumor, the presence of melanoma metastases in the sentinel lymph node,  as well as the age of patients and the driver mutation of the tumor were demonstrated. Lymphadenectomy performed after a biopsy of the signaling lymph node and the localization of the tumor had no effect on the disease outcome.

The Ewing sarcoma is one of the two most common bone tumors that occur during childhood and adolescence. This pathology in more than 50 % of cases occurs in the 2nd decade of life and is rare in adults older than 30 years. In men, the Ewing sarcoma develops more often (male-to-female ratio is 1.5:1). This disease is rare in Black patients and Asians. Ewing sarcoma usually occurs in the metaphysis or diaphysis of the long bones of the extremities. Lesions of the pelvic region, ribs and shoulder blades are less common. The most common foci of metastasis are the lungs, bones, and bone marrow.

The article describes a clinical case of treatment of a 12-year-old girl with Ewing sarcoma of the pelvic bones (chemotherapy with a surgical stage: single-stage bone grafting of the resected section of the pubic bone using a rib graft).

Multiple exostosis disease is a rare genetic disorder manifesting in skeletal lesions with development of multiple progressing deformations of the bones and joints. This pathology is characterized by high risk of malignant tumors accompanying bony outgrowths, primarily, chondrosarcoma with onset at the age of 20–40 years. Development  of multiple exostosis disease is mediated by pathogenic variants in the EXT1, EXT2 and EXT3 genes which are inherited through autosomal dominant type of inheritance with high penetrance. During diagnosis in children, this pathology should be differentiated from progressing ossifying fibrodysplasia, metachondromatosis, Langer–Giedion syndrome and common malignant tumors of the bones, cartilage and soft tissues.

 The article presents 2 clinical observations of treatment of multiple exostosis disease. In the first case, familial form of the disease with transmission of pathogenic variant in the EXT1 gene from the father and development of chondrosarcoma in both sons  at the ages of 17 and 21 years is described. In the second case, previously not described pathogenic variant in the EXT1 gene identified de novo in a 12-year-old patient with Ewing sarcoma is presented. These observations demonstrate  the necessity of early oncological screening in patients with multiple exostosis disease.