Pregnancy-Associated Progression with Spontaneous Postpartum Regression in Metastatic Alveolar Soft Part Sarcoma- A Case Report and Literature Review

We report the case of a woman in her late thirties with metastatic alveolar soft part sarcoma (ASPS). Her pulmonary lesions increased in size after a miscarriage and during a subsequent pregnancy, prompting consideration for systemic treatment and potential enrollment in a clinical trial of tyrosine kinase inhibitor plus immunotherapy. At the time of trial screening, however, a baseline staging CT performed a few weeks postpartum unexpectedly demonstrated marked regression. Because enrollment required radiographic progression, she was excluded from trial participation, and no systemic therapy was initiated. Surveillance imaging over the following two years confirmed continued regression of the residual lesion. This case may reflect the influence of pregnancy-to-postpartum physiology on tumor behavior through hormonal, immune, and angiogenic pathways, and it emphasizes the importance of reassessment after delivery before systemic therapy is considered.