Surgical Strategies for Unexpected Unilateral Absence of the Latissimus Dorsi Muscle during Breast Reconstruction: A Case Report and Literature Review.

The latissimus dorsi (LD) muscle is considered one of the most reliable donor sites for autologous breast reconstruction, particularly in patients with prior oncologic treatment or comorbidities precluding microsurgical options. While its consistent anatomy typically permits straightforward surgical planning, rare anatomical anomalies can dramatically alter intraoperative decision-making. We report the case of a 69-year-old woman with a long oncologic history and multiple comorbidities who underwent delayed breast reconstruction using a pedicled LD flap, 1 year after radical mastectomy and axillary lymphadenectomy. Intraoperatively, the LD muscle was found to be completely absent on the left side, with no identifiable muscle belly and tendon. Immediate adaptation was required, and a serratus anterior muscle flap based on a thoracodorsal branch was used instead. Interestingly, retrospective review of a CT scan performed 2 years earlier for a pulmonary complaint revealed clear evidence of unilateral LD muscle absence, an oversight that underscores the importance of targeted imaging review. This case is one of only four reported in the literature, where unilateral absence of the LD muscle in a non-syndromic patient was encountered, and the only one intraoperative discovery during breast reconstruction. This highlights the critical need for anatomical vigilance and intraoperative adaptability in reconstructive surgery. When standard options fail, familiarity with alternative flaps and sequential planning are essential to achieving functional and aesthetic outcomes.