Histopathological evaluation of benign soft tissue lesions at Nnamdi Azikiwe University teaching hospital, Nnewi, south-east Nigeria: A 9-year review

Background: Soft tissue lesions are remarkably diverse and range from inflammatory, self-limited lesions to neoplasm. The diversity of these lesions frequently poses a diagnostic challenge to pathologists and remains a subject of interests. Lack of research on soft tissues in our setting has prompted the need to study them. Objectives: The aim of this study was to determine the benign lesions of soft tissues with respect to age, sex, anatomic site, and histologic types. It also aimed to determine the baseline data of benign soft tissue lesions in Nnewi, Nigeria. Materials and Methods: This study reviewed all histologically diagnosed benign soft tissue lesions at the Histopathology Department of Nnamdi Azikiwe University Teaching Hospital (NAUTH), Nnewi, Nigeria from 2011 to 2019 and classified the tumors using the 2020 WHO Classification of Soft Tissue Tumours. Results: A total of 351 cases of soft tissue lesions were diagnosed during the study period, out of which 251 were benign lesions and accounted for 71.5% (251/351) of all soft tissue lesions, whereas 28.5% (100/351) of the cases were malignant. The benign lesions included inflammatory and benign neoplasm, of which neoplasm accounted for the majority of the cases with a frequency of 94.0% (236/251), whereas inflammatory lesions accounted for 5.9% (15/251). The 236 benign soft tissue tumors diagnosed had a male-to-female ratio of 1: 1.4 with a mean age (SD) of 37.5 (19.5) years. The most frequent occurrence of benign tumors was seen in the fourth decade with 52 cases (21.0%), followed by fifth decade with 42 cases (16.7%). Adipocytic tumors were the commonest with a frequency of 54.0% (135/251), followed by peripheral nerve sheath tumors (PNSTs) with 12.4% (31/251) and then vascular and fibroblastic/myofibroblastic tumors with 10.8% (27/251) and 5.6% (14/251), respectively. Lipoma is the most common histologic type of benign soft tissue tumor and the only benign adipocytic tumor. This is followed by hemangioma 9.6% (24/251) and then neurofibroma 7.6% (19/251). Lipoma accounted for 37.09% (135/351) of all soft tissue lesions and the majority of them were seen in the fourth decade, whereas hemagioma and neurofibroma occurred more at the first decade. The most common anatomic distributions of these benign tumors were lower extremities with 23.5% (n = 59/251), followed by trunk 21.1% (n = 53). The major inflammatory lesions were tuberculoid granulomatous inflammation and panniculitis with 2.3% (6/251) of cases each. Others were necrotizing fasciitis (n = 2) and eosinophilic myositis (n = 1). Conclusion: Benign soft tissue tumors had a slight female preponderance. Lipoma is the single most common benign soft tissue neoplasm, whereas tuberculosis and panniculitis were the two most common inflammatory soft tissue lesions. Histopathological evaluation of these lesions still stands as a gold standard in their diagnosis.