Atypical lipoma, commonly referred to as a "deep-seated" or "intramuscular lipoma," is a benign tumor that develops within the soft tissue of the body. Some synonyms for atypical lipoma include spindle cell lipoma, pleomorphic lipoma, and intramuscular lipoma. These tumors have distinguishing characteristics such as the presence of an abnormal cell growth pattern and increased vascularity. While typically slow-growing and non-cancerous, these tumors can occasionally cause pain or discomfort and may require surgical removal. It is important to carefully monitor any atypical lipomas and seek medical attention if they begin to grow or cause discomfort.