Not all lumps and bumps are tumors. There are many conditions that can cause masses or lumps in soft tissue that have nothing to do with tumors.
An infection or abscess is perhaps the most common cause behind a mass that is mistaken for a tumor. In addition, cysts may arise from inflamed joints or tendons as a result of injury or degeneration. Inflammatory conditions, such as rheumatoid arthritis, can also result in soft tissue masses. Even metabolic conditions, such as hyperlipidemia (high blood fat levels), can cause masses to form that may look like tumors. Baker’s cyst behind the knee, gouty deposits about the elbow and vascular aneurysms are examples of non-tumor masses that require a medical assessment.
Similarly, there are many conditions that can cause changes in a bone that may resemble a tumor. Bone infection (osteomyelitis) can cause such changes. Metabolic conditions such as hyperparathyroidism can cause tumor-like areas to form. These will go away if the underlying problem with the parathyroid gland is treated. Other metabolic or congenital conditions of bone such as Paget's Disease, fibrous dysplasia, osteopetrosis, melorrheostosis, fibroosseous ossificans progressiva, and tumoral calcinosis have a characteristic appearance and require a unique treatment approach.
Perhaps one of the most difficult diagnoses to miss is that of idiopathic myositis ossificans. In this condition, an individual may present with a rapidly growing painful mass. An X-ray will show rapid bone formation, which can look identical to a high-grade osteosarcoma. In this case, however, the bone formation is a reactive inflammatory process that will stop. Urgent surgery usually makes this worse. There have even been unfortunate occasions where amputations have been performed for this essentially benign, though frightening, condition when mistaken for a malignant tumor.