Epidemiology and Clinical Features
The incidence of various mesenchymal neoplasms varies. Their clinical properties depend directly on their histogenesis, specific anatomic location, as well as the patient's sex and age.
- Lipomas: These are the most common soft tissue tumors, accounting for about one-third of all cases. As a rule, they are entirely painless and diagnosed predominantly in adult patients. Localization on the hands or lower extremities is extremely rare.
- Multiple angiolipomas: Unlike classic lipomas, these lesions are tender on palpation and are most typical for young adult males.
- Vascular tumors: Account for approximately 10% of all cases. The vast majority of these neoplasms are identified in pediatric patients and individuals under the age of 20.
- Angioleiomyomas: Predominantly affect the lower extremities and are most frequently diagnosed in middle-aged women.
Etiology and Pathogenesis
The etiology of most mesenchymal tumors remains undetermined. The pathogenesis is also not fully defined, though it is believed that the vast majority of sarcomas arise primarily, or de novo. However, scientific data support the existence of a pre-sarcoma stage characterized by the gradual accumulation of genetic alterations (mutations) in cells.
Several key risk factors and associations are distinguished:
- Chemical carcinogens: Contact with dioxins found in herbicides and plastics reliably increases the risk of sarcoma development.
- Radiation exposure: Associated with the development of post-radiation malignant histiocytomas and osteosarcomas.
- Viral agents: The oncogenic role of herpesviruses and Epstein-Barr virus (EBV) has been demonstrated.
- Hereditary predisposition: Familial cases of lipomas and angiolipomas have been described. Additionally, sarcomas frequently develop in the setting of severe genetic syndromes, such as Li-Fraumeni syndrome (linked to TP53 tumor suppressor gene mutations) and hereditary retinoblastoma (caused by Rb tumor suppressor gene mutations).
Benign Tumors
Benign mesenchymal neoplasms are dominated by adipose tissue tumors. The primary and most frequent type is the lipoma. In addition, a spectrum of related pathologies exists: lipomatosis, lipoblastoma (and lipoblastomatosis), angiolipoma, myolipoma, hibernoma, as well as specific variants including chondroid, spindle cell, and pleomorphic lipomas.
The most commonly recognized benign tumor overall is the leiomyoma. It typically localizes in the uterus, gastrointestinal tract, and urinary bladder. An important histogenetic feature is that, regardless of the affected organ, leiomyomas originate from vascular wall pericytes. When uterine leiomyomas feature a heavily developed connective tissue stroma, the more precise term leiomyofibroma is used.
Malignant Tumors (Sarcomas)
Malignant mesenchymal neoplasms are grouped under the general term sarcomas. They exhibit pronounced signs of malignancy, characterized by rapid infiltrative growth with destruction of surrounding tissues and early hematogenous metastasis. Extensive secondary changes—such as massive areas of tissue necrosis, myxoid change, hemorrhage, and calcification—are frequently observed within the tumor mass.
A distinct and important group comprises liposarcomas, the malignant counterparts of adipose tumors. Depending on their histological structure, they are classified into several types:
- Well-differentiated.
- Dedifferentiated.
- Myxoid.
- Pleomorphic.
- Mixed-type liposarcoma.
Hereditary Tumor Syndromes
According to the WHO classification, a distinct group of hereditary syndromes exists in which tumors develop within endocrine organs. The primary syndromes include Multiple Endocrine Neoplasia (MEN) type 1, MEN type 2 (including variants 2, 2A, and 2B), Neurofibromatosis type 1, and hyperparathyroidism-jaw tumor syndrome.
MEN type 2 (Sipple syndrome) warrants special attention in clinical practice. This is an autosomal dominant disorder caused by a germline mutation in the RET (Rearranged during Transfection) proto-oncogene.
Clinical manifestations include the classic triad:
- Thyroid tumors (medullary thyroid carcinoma).
- Adrenal tumors (pheochromocytomas).
- Primary hyperparathyroidism (parathyroid gland involvement).
The syndrome occurs with a frequency of 1.25 to 7.5 cases per 10,000,000 population. Notably, it accounts for 25% of all hereditary forms of medullary thyroid carcinoma. The disease may present with associated pathologies such as Hirschsprung disease and cutaneous amyloidosis. Diagnosis is based on a combination of clinical manifestations and mandatory detection of the RET gene mutation.