Angiomatous leiomyoma of the urachus: A rare entity masquerading as extraluminal gastrointestinal stromal tumor

Abstract

The urachus is a vestigial structure located between the dome of the bladder and the umbilicus, which results from the involution of the allantoic duct and the cloaca. Persistence of an embryonic urachal remnant can cause various problems during childhood and young adulthood. Urachal leiomyoma is a rare entity with very few cases being reported in literature. It can be misdiagnosed and confused with a wide spectrum of intra-abdominal or pelvic disorders. We hereby report a case of angiomatous leiomyoma originating from the urachal remnant in a 45-year-old lady, masquerading as extraluminal gastrointestinal stromal tumor. Understanding the embryological basis of these urachal disorders and their imaging features coupled with histopathological examination is crucial for the correct diagnosis and management. Pathological diagnosis is required to optimize the surgical approach and preclude unnecessary radical surgery.

Keywords: Urachus; angiomatous; leiomyoma.

Figure 1

(a) CT scan of the abdomen and pelvis revealing a well-defined heterogeneous, mildly enhancing, predominantly hypodense lesion measuring 5.8 × 3.6 cm attached to the anterior abdominal wall at the umbilicus (yellow dotted line). (b) CT scan revealing the mass lying anterosuperior to the bladder on the right side and in close proximity to the right rectus muscle (yellow dotted line)

Figure 2

(a) External surface of the lesion showing a well-encapsulated smooth nodular mass measuring 6 × 5 × 3.5 cm, with a few congested blood vessels. (b) The cut surface of the mass showing solid homogeneous gray-white appearance

Figure 3

(a) Microscopic examination revealing a benign tumor comprised of spindle-shaped cells arranged in interlacing fascicles and whorls. The stroma shows myxoid change along with numerous thick-walled blood vessels (H and E, ×100). (b) Numerous thick-walled blood vessels are evident with their inner muscle layer arranged circumferentially and outer layer blending with the less well-ordered smooth muscle of the tumor (H and E, ×400)

Figure 4

Immunohistochemically, the tumor cells show positivity for (a) SMA (×100), and (b) desmin (×100), and (c) negativity for CD117 (×400), (d) the vessels show immunoreactivity for CD34 (×100)