DFs are now identified as several malignant tumours in addition to collagenous fibromas. Some benign soft tissue tumours are uncommon. It is crucial to accurately locate and treat DF since, although innocuous, it may be harmful in specific areas. This is why its diagnosis is crucial. As the case presented, the patient’s pain was caused by a left sternoclavicular invasion. The patient’s 53-year-old age presented a sign of discomfort. Because of this invasion, the patient’s agony increased. Medical experts believed (DF) would be most likely to be discovered. Because several imaging tests, including an MRI, failed to rule out haemangiomas. The surgeon removed a large pectoralis major muscle tumour immediately after therapy. This happened after treatment, this mass had lobules. Haematology gave a lot of evidence that confirmed DF caused the aberrant blood cell count. The evidence included a hypocellular spindle-shaped lesion without necrosis or mitotic activity. Additionally, the stroma had significant collagenization. The disease has not returned for six months after a complete surgical excision, proving that the procedure was successful from the start. Given the details of this instance, a histology test is essential to diagnose DF. In contrast, this case summarizes the diagnosis process and discusses the similarities between this tumour and other soft tissue cancers. Additionally, this case summarizes the diagnostic procedure. Although diagnosing this illness may be difficult, it is nonetheless possible. This shows that comprehensive surgical excision is the most effective method and emphasizes the necessity for long-term surveillance to detect any illness recurrence. Because the illness has demonstrated it may recur. Many medical experts must collaborate to identify and treat (DF). Further study is needed on DF’s causes and treatments.