Complicated Extra-Abdominal Desmoid Tumor Associated With Pregnancy in a Patient With a History of Bilateral Mastectomy: A Case Report.

Desmoid-type fibromatosis is an uncommon, locally aggressive, non-metastatic soft-tissue neoplasm that accounts for <0.03% of all tumors; breast or multifocal disease is particularly rare, and the hormonal milieu of pregnancy may accelerate tumor growth. We report an 18-year-old primigravida who underwent bilateral mastectomy at age 17 for presumed phyllodes tumors that were subsequently reclassified as bilateral breast desmoid tumors on histopathologic review. During her current pregnancy, she developed two rapidly enlarging abdominal-wall masses, one becoming necrotic and infected, necessitating multidisciplinary evaluation. At 33 weeks' gestation, a cesarean section was performed via a left paramedian incision that avoided the tumors, delivering a viable male infant; the mother was then referred to a tertiary oncologic center for definitive management. This case illustrates the diagnostic uncertainty, potential for rapid progression, and need for individualized, multidisciplinary care when desmoid tumors arise or recur during pregnancy to balance maternal oncologic control with fetal well-being.