Intramuscular atypical lipomatous tumor/well-differentiated liposarcoma of the pectoralis major masquerading as a breast tumor: management and review of the literature.

Atypical lipomatous tumor (ALT)/well-differentiated liposarcoma (WDL) of the pectoralis major muscle is an exceedingly rare clinical entity. We describe here a case of intramuscular ALT/WDL of the pectoralis major muscle in a female patient who presented with clinical manifestations of a rapidly growing breast tumor. Diagnostic evaluation and management of the patient are discussed along with a review of the relevant literature. We conclude that although the clinical examination may be inconclusive, the mammogram and especially the magnetic resonance imaging scan can precisely delineate the anatomic location and extent of the ALT/WDL of the pectoralis major muscle, thus allowing a correct preoperative diagnosis and adequate preoperative surgical planning. Complete resection is the treatment of choice for ALT/WDL. Long-term follow-up, however, remains mandatory because of the risk of local recurrence or delayed dedifferentiation.