Prevalence of Soft Tissue Tumours in Duhok-Iraq: A Practical Immunohistochemical Approach

Introduction: The field of Soft Tissue Tumours (STT) is enormously vast, and yet histologically and relatively vague. Although benign tumours are more common than malignant tumours, the relative rarity of sarcomas, little knowledge, and insufficient local studies, made the authors eager to search more through this field and explore the hidden and unobvious features of these tumours in our locality. Aim: The study aimed to apply traditional and updated antibodies to characterise STT in Duhok-Iraq, morphologically and immunohistochemically. Materials and Methods: In this cross-sectional study, 886 STT were received in the Department of Histopathology in Central General Laboratories and Vin Private Laboratories, Duhok-Iraq, over a period of 11 consecutive years (January, 2009 to December, 2019). Cases were studied clinically and then, morphologically categorised. Immunohistochemical workup was performed when needed, to sub-classify undifferentiated tumours. Results: Benign tumours (n=768) ovarian sarcomas (n=118) by a ratio of 6.5:1, both showed a wide age range (1 month to 82 years), with peak in the fourth decade and with no sex predilection. Also, limbs were more commonly affected by both benign and malignant tumours. Lipomas topped the benign STT 328 (42.7%) followed by vascular tumours 178 (23.2%). Regarding sarcomas, 29 (24.5%) remained unclassifiable and were typed as Sarcoma Not Otherwise Specified (NOS). For the specifically diagnosed malignancies, leiomyosarcoma 24 (20.3%) topped the list, followed by rhabdomyosarcoma and Ewing’s/Primitive Neuroectodermal Tumour (PNET) 12 (10.1%) each, Dermatofibrosarcoma Protuberans (DFSP) and liposarcoma 11 (9.4%) each and synovial sarcoma 6 (5.1%). Conclusion: Benign STT were more common than sarcomas. Diagnosis and classification of STT should be based on acumen histologic grounds which is sufficient for most benign tumours and to some extent for sarcomas. Undifferentiated sarcomas cannot be categorised without immunohistochemistry. However, loss of some differentiation antigens in undifferentiated cancers often necessitate the use of panels of antibodies, and considerable cases even need further evaluation, like molecular studies.