What happened, in summary

A previously healthy 36-year-old woman developed shortness of breath and chest pain after losing consciousness while driving and crashing her car. CT angiography and a ventilation-perfusion scan found no pulmonary embolism, but imaging showed abnormal thickening in both lungs. Echocardiography and right-heart catheterization confirmed severe pulmonary arterial hypertension. Spine imaging also revealed fractures and destructive lesions at several vertebrae.

She had recently been told that a screening mammogram showed a left-breast abnormality. An inpatient breast biopsy identified invasive mammary carcinoma that was estrogen-receptor positive and progesterone-receptor positive. Bone-marrow biopsy showed near-total replacement by cancer cells, confirming metastatic breast cancer. Clinicians strongly suspected pulmonary tumor thrombotic microangiopathy or tumor emboli, although pulmonary-artery cytology was negative and the diagnosis could not be proven histologically.

Sildenafil was started for pulmonary hypertension, followed urgently by weekly paclitaxel, leuprolide, and zoledronic acid. Prednisone was added for the suspected pulmonary vascular complication. Within days, her oxygen needs and cardiovascular measurements improved. Ten days after treatment began, right-ventricular size, function, and pressure had normalized. She left hospital with temporary home oxygen, later tapered off oxygen and steroids, completed radiation, and continued systemic therapy. PET imaging showed a marked response. Seven months after diagnosis, she was doing well and continuing treatment with palbociclib.