Latissimus Dorsi Muscle Went Undetected for Decades Until Surgery Exposed Its Absence

In April, a Brazilian surgical team discovered that a 62-year-old woman undergoing delayed breast reconstruction was completely missing her right latissimus dorsi. Six weeks later, a Swiss team reported an almost identical finding in a 69-year-old patient.

Neither woman had any clue. Both had lived into their sixties without one of the body’s largest back muscles—and without a single symptom that would have flagged its absence.

A Major Muscle That Can Vanish Without a Trace

The latissimus dorsi is a broad, flat sheet extending from the lower thoracic spine, lower ribs, and pelvis to the upper arm bone. It assists arm movement and breathing and is a workhorse donor site in reconstructive surgery, including free flaps for severe lower limb injuries.

Yet losing it on one side produces no dependable warning. The Swiss patient reported no shoulder dysfunction and no visible thoracic asymmetry, so a routine flap was anticipated. Surrounding muscles appear to compensate well enough that everyday function remains unaffected.

This silence is precisely what makes the anomaly so elusive. It is not caught on a physical exam or when someone struggles with a heavy door. It surfaces only when a surgeon goes looking for the muscle and finds it missing.

The implication is that published cases likely underrepresent the true frequency. Anyone born without the muscle who never needs reconstructive surgery, never has a chest scan evaluated for back musculature, and never notices a functional problem has no path to diagnosis.

Two Surgeries, Two Very Different Outcomes

The Brazilian case, published in Plastic and Reconstructive Surgery Global Open, involved a mastectomy patient needing delayed reconstruction. Dissection confirmed total absence of latissimus tissue, but the thoracodorsal artery and vein were intact in the subscapular region. The team converted to a thoracodorsal artery perforator flap, using skin and fat supplied by perforating branches instead of the muscle itself. The reconstruction succeeded.

The Swiss case, reported by Luzerner Kantonsspital in Archives of Plastic Surgery, took a rougher turn. The patient had undergone axillary lymph node removal a year earlier, and scar tissue made vascular dissection difficult. The thoracodorsal artery and nerve could not be reliably identified, forcing harvest of serratus anterior on alternative vessels. The flap later developed venous congestion and partial necrosis, requiring debridement and a skin graft.

The contrast underscores a key point: whether an intact thoracodorsal pedicle survives prior surgery largely determines what a team can do when the muscle is absent.

The Scan That Showed It All Along

The Swiss team reviewed their patient’s records and found a chest CT ordered two years earlier for a lung issue. It showed the missing muscle plainly—yet the finding had gone unrecognized.

This is not simply a reading error, and the authors frame it as a lesson about targeted review rather than negligence. Nobody scanning for a pulmonary problem is examining the latissimus dorsi. And because latissimus anatomy is assumed to be highly consistent, the muscle is treated as a reliable donor site without preconfirmation.

The old scan also ruled out alternative explanations. Because it predated her mastectomy, axillary surgery, and radiation, it excluded nerve injury and post-radiation atrophy. The muscle had never formed.

What Is Known—and What Remains Uncertain

Two case reports cannot establish prevalence, and neither team claims one. Congenital absence of a single muscle is documented far more often for the pectorals—most familiarly in Poland syndrome—than for the latissimus.

One anatomical report described a 73-year-old female cadaver in whom the left latissimus dorsi could not be identified, aside from a few small fibers from the lower thoracic segments, along with a missing thoracodorsal nerve and absent arterial branches. The same specimen had a spine curving toward the opposite side. One cadaver cannot confirm whether the two findings were related.

On the other side, there is better evidence from patients who have the muscle and lose it to surgery. A case-control cohort study in the British Journal of Surgery compared shoulder and back function after flap reconstruction using validated questionnaires. That work addresses the consequences of harvesting the muscle, not being born without it.

For patients considering reconstruction, none of this is cause for alarm, and no test is warranted on the strength of two case reports. The more useful step is discussing donor site planning and backup options with the surgical team. Both reports were published without funding, and all authors declared no conflicts of interest.

Key Questions Answered

What is the latissimus dorsi and what does it do?

It is a large flat muscle of the lower back that helps move the arm and assists breathing. It is also one of the most commonly used donor muscles in reconstructive surgery.

How can someone not know a muscle is missing?

Neighboring muscles appear to compensate. In the Swiss case, the patient reported no shoulder dysfunction and had no visible asymmetry, so nothing prompted investigation.

Why did the two operations go so differently?

In the Brazilian case, the thoracodorsal blood vessels were intact, allowing conversion to a perforator flap. In the Swiss case, a previously operated armpit made those vessels hard to identify, forcing a less favorable salvage.

Does a missing latissimus cause scoliosis?

That has not been established. One cadaver report describes both findings in the same body, which is a coincidence in a single specimen rather than evidence of cause.

Should patients planning reconstruction ask for a scan?

Two case reports do not justify a new imaging requirement. A more useful step is discussing donor site planning and backup options with the surgical team.

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