Red degeneration of a leiomyoma

Last revised by Mohamed Saber on 18 Jan 2023

Red degeneration, also known as carneous degeneration, is one of four main types of degeneration that can involve a uterine leiomyoma. While it is an uncommon type of degeneration, it is thought to be the most common form of degeneration of a leiomyoma during pregnancy 3.

Patients with a leiomyoma undergoing red degeneration may present with abdominal pain (particularly during pregnancy). It may also give systemic symptoms such as fever and leukocytosis. 

Carneous degeneration is a subtype of hemorrhagic infarction of leiomyomas that often occurs during pregnancy. On gross pathology, it is characterized by a red (hemorrhagic) appearance of the leiomyoma. Red degeneration primarily occurs secondary to venous thrombosis within the periphery of the tumor or rupture of intratumoral arteries 4.

Unusual signal intensity patterns have been described on pelvic MR imaging 1,4:

  • T1
    • can have peripheral (rim) or diffuse high signal intensity
    • high signal intensity on T1-weighted images is likely secondary to the proteinaceous content of the blood or the T1-shortening effects of methemoglobin
  • T2 
    • variable signal intensity with or without a low-signal-intensity rim
    • when high signal intensity is isolated to the rim of the leiomyoma, it has been hypothesized that the blood products are confined to thrombosed vessels that surround the tumor
    • when it shows rim - peripheral changes these findings were thought to correspond to numerous dilated vessels filled with red blood cells at the periphery of the lesion
    • the signal characteristics of the rim are best explained as an effect of abundant intracellular methemoglobin in these vessels 
  •  T1 C+ (Gd): variable enhancement

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