Case Presentation: A 31-year-old female with no pertinent past medical history presented first with right upper quadrant (RUQ) abdominal discomfort a year after giving birth to her first child in 2018. Prior to pregnancy, patient was taking oral contraceptives for nine years. The pregnancy was complicated by severe preeclampsia and associated nephrotic syndrome and LFT disarrangement. In clinic, patient complained of a mild dull pain, aggravated by activity. Vital signs were unremarkable. CT and subsequent MRI revealed a large liver mass, characterized as a 7 by 6 cm focal nodular hyperplasia (FNH) lesion. Surgery was discussed but the patient declined. Months later, repeat imaging showed the mass was slightly larger, and surgery was again discussed as an option, as symptoms of RUQ discomfort had worsened.IR was consulted and patient was deemed a candidate for bland embolization for tumor size reduction, which the patient opted for over surgical resection. IR embolization was conducted with symptom resolution in 2 months and no recurrence during strenuous activity. Follow-up months later was unremarkable. Patient became pregnant again in late 2019 and complained of a similar RUQ abdominal pain. The pregnancy resulted in a miscarriage, but the liver mass was witnessed again. IR embolization was conducted with the resolution of symptoms thereafter. Patient became pregnant for a third time with a full-term baby, delivering at the end of 2020 (G3P2). Patient again presented with RUQ abdominal discomfort with a decreased severity. MRI abdomen showed a 5.2 by 4.5cm FNH lesion, and IR embolization was conducted with the resolution of symptoms and in anticipation of further pregnancies.

Discussion: Focal nodular hyperplasia (FNH) is a common benign hepatic mass with a prevalence of 0.3-3% in adults. FNH is characterized by the proliferation of hepatocytes as a hyperplastic reaction to vascular or circulatory abnormalities, such as congenital vascular malformations, dystrophic arteries, or portal tract injuries. It is generally asymptomatic but can present as abdominal pain, especially when the abdominal mass exceeds 10 cm. It is most often discovered incidentally on imaging when patients present with nonspecific symptoms such as abdominal pain. FNH tends to have a predilection towards women ages 20-50, suggesting a possible correlation between estrogen levels and the incidence of this condition. Furthermore, women also present with larger nodules than men. It was initially believed that taking daily oral contraceptives (OCPs) was related to the incidence of FNH. However, recent literature has not found a significant correlation between OCP use and the incidence of FNH, the size, or the number of lesions. The role of hormones in FNH remains controversial, although, there have been many cases correlating increased tumor size with prior OCP use and regression after discontinuation. Similarly, there have been some reports of an increase in the size of lesions found during pregnancy and subsequent regression after delivery.

Conclusions: This case aims to highlight and reiterate the possible association of estrogen-related and pregnancy-related FNH, as seen with persistent recurrence of FNH after each pregnancy in this patient. This case aspires to encourage clinicians to consider prophylactic IR embolization for future pregnancies in patients presenting with a similar etiology. Due to the rising incidence of FNH in women of child-bearing age and the disputed nature of its hormonal association, further research is necessary.

IMAGE 1: MRI of the FNH Liver Mass