Abstract 82P
Background
Malignant peripheral sheath tumor (MPNST) is a rare malignant soft tissue tumor with complex morphological appearance. Some cases are associated with type I neurofibromatosis (NF1). It has a wide range of involved location in the body and with aggressive clinical outcome. We tried to summarize the clinical and pathological characteristics of MPNST cases in our center, to improve our understanding.
Methods
This is a retrospective study enrolled 134 cases of MPNST at Cancer Hospital of the Chinese Academy of Medical Sciences from April 2017 to December 2022, including 99 consultative cases. We summarized the clinical-morphological characteristics.
Results
There were 64 males and 70 females enrolled in the study, with an average age of 44.3 years (range 4-83 years), including 6 patients with neurofibromatosis type I. A total number of 14 patients experienced tumor recurrence or metastasis. The above tumors are distributed in 150 affected areas, with the majority occurring in the trunk (46 cases), followed by the limbs (34 cases), the head and neck (33 cases), internal organs (22 cases), and the female reproductive system (6 cases). The thighs, neck, and back were the three most common affected areas, all with dense distribution of somatic nerves. There were 16 cases involved the skull. The classic MPNST with typical focal necrosis, inflammatory cell infiltration, and mitosis count >20/10HPF are the main subtypes, followed with 10 cases of low-grade and epithelioid MPNST. Among them, 7 cases showed rhabdomyoma differentiation (malignant salamander tumor). The immunophenotype exhibits various expression level of neurogenic markers (S100 and SOX10), negative or weakly positive for epithelial markers. The Ki67 index shows a high proliferative activity of over 30% in most cases. The deficiency of H3K27me3 was found in 23 out of 34 test cases (67.6%).
Conclusions
MPNST is a rare sarcoma always affected middle-aged and elderly patients., with various morphological appearance. The expression of immunohistochemical markers S100 and SOX10, as well as the loss of H3K27me3 expression is of great diagnostic value. MPNST shows frequent incidence of recurrence and metastasis. It is urgent to explore effective targeted and new therapies to improve prognosis.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The author.
Funding
Department of Pathology, National Cancer Center.
Disclosure
The author has declared no conflicts of interest.