REVIEW ARTICLE Soft Tissue Sarcomas: An Overview on Histomorphology Shameera Begum 1 , Shanmugasamy Kathirvelu 2 , Anandraj Vaithy 3 , Sowmya Srinivasan 4 A BSTRACT Background: Soft tissue sarcomas (STS) comprise a diverse group of rare malignancies that arise from connective tissues. The natural course of STS is unpredictable and aggressive if not diagnosed at an early stage. Discussion: The subclassifcation of these tumors is important for prognosis and clinical management of patients. In the present review, we discuss the histomorphologic features of STS and its subtypes based on 2013 World Health Organization classifcation and throw light on the incidence and presentation of STS. Conclusion: The systematic approach to morphologic assessment of STS outlined in this review will lead to narrowing of diferential diagnoses and pave way for efective diagnosis and implementation of treatment strategies. Keywords: Classifcation of soft tissue sarcomas, Histomorphology, Malignant soft tissue tumors, Sarcomas. Annals of SBV (2019): 10.5005/jp-journals-10085-8114 I NTRODUCTION Soft tissue sarcomas (STSs) are tumors arising from mesodermal portion of the embryo that develops into connective and skeletal tissues. They are uncommon tumors comprising less than 1% of all malignant tumors. The overall annual incidence of STS is about fve cases per 100,000 population. 1 Although rare, they are life threatening and cause signifcant diagnostic and therapeutic challenges. Soft tissue sarcomas can occur at any age and are most common among middle-aged and older adults. They are relatively common in children and young adults constituting 7–10% of pediatric malignancies. 2 Most of them are known to arise from retroperitoneum, trunk, and extremities. The exact etiology of STS is unknown. While few tumors are said to have genetic association such as 10% lifetime risk of malignant peripheral nerve sheath tumors in individuals with familial neurofbromatosis, majority arise de novo with contributions by environmental factors, irradiation, viral infections (human herpes virus 8), and immunodefciency states. 2 Soft tissue sarcomas present as painless masses in general, and they are usually large at the time of presentation. Metastasis is in the hematogenous route, and the most common site is lungs. Magnetic resonance imaging is the investigation of choice due to multiplanar imaging and better tissue discrimination. Final diagnosis is by histopathological examination, as it allows diferentiation of benign from malignant cases and in cases of malignancy reports the histologic grade and subtype of sarcoma. 3 Treatment of STS warrants a multidisciplinary approach. High-grade sarcomas are treated with excision and postoperative radiotherapy. Major advances in the feld of immunohistochemistry, cytogenetics, and molecular genetics have led to significant changes in the diagnosis, clinical management, and prognosis of STS. According to 2013 World Health Organization (WHO) classification, STSs are organized into the following nine groups: adipocytic, fibroblastic/myofibroblastic, the so-called fbrohistiocytic, perivascular, vascular, smooth muscle, skeletal muscle, chondro-osseous tumors, tumors of uncertain diferentiation, and undiferentiated sarcomas. The most common histologic subtypes in adults are undifferentiated sarcomas, liposarcoma (LPS), synovial sarcoma, leiomyosarcoma, and malignant peripheral nerve sheath tumor. In the present review, we discuss the histomorphologic features of STS and its subtypes based on 2013 WHO classifcation and shed light on the incidence and presentation of STS. H ISTOMORPHOLOGICAL F EATURES OF STS Adipocytic Tumors Liposarcoma Liposarcoma is the most common subtype of STS, constituting 20% of all adult STS. There are four histological subtypes based on clinicopathological characteristics: well-diferentiated LPS, myxoid LPS, dediferentiated LPS, and pleomorphic LPS. Well-diferentiated LPS/Atypical Lipomatous Tumor It occurs in adults from fifth to eighth decade with common presentation in the thigh and retroperitoneum. Tumor is grossly lobulated with yellow to white external surface and cut surface that is soft to frm. It is composed of sheets of mature adipocytes showing significant pleomorphism and minimal focal nuclear atypia. Presence of scattered multinucleate and hyperchromatic stromal cells with lipoblasts of varying number contribute to the diagnosis. The rate of recurrence is high in patients with retroperitoneal well-diferentiated LPS (Fig. 1). 1 1–4 Department of Pathology, Mahatma Gandhi Medical College and Research Institute, Pillayarkuppam, Puducherry, India Corresponding Author: Shanmugasamy Kathirvelu, Department of Pathology, Mahatma Gandhi Medical College and Research Institute, Pillayarkuppam, Puducherry, India, Phone: +91 9487920242, e-mail: shanmugasamyk@mgmcri.ac.in How to cite this article: Begum S, Kathirvelu S, Vaithy A, Srinivasan S. Soft Tissue Sarcomas: An Overview on Histomorphology. Ann SBV 2019;8(2):45–50. 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