Inguinal canal lipomas (also known as spermatic cord lipomas, peritesticular lipomas, and round ligament lipomas), are a relatively common but often under-recognised finding on imaging.

Terminology

'Spermatic cord lipoma' is variably used to mean a true lipoma of the spermatic cord (originating from adipose cells and with no communication with the inguinal canal), an inguinal canal lipoma (extraperitoneal fat extension through the inguinal canal), or a hernia of intraperitoneal fat through the inguinal canal, with or without a hernial sac ⁵.

Clinical presentation

Lipomas are usually asymptomatic but can sometimes cause pain and discomfort. They can present as a non-tender soft scrotal mass ⁴. 

Pathology

They have no communication with the peritoneal fat. They are not considered true tumours of fat but extrusions of extraperitoneal fat extending into the inguinal canal. 

Radiographic features

Ultrasound

It is seen as a well defined, solid hyperechoic mass, expanding the inguinal canal, which gently effaces the spermatic cord.

CT

The lesion shows attenuation corresponding to fat (-20 to -70 HU). No associated soft tissue component or enhancement.

MRI

Oval shaped mass with typical fat signal characteristics:

• T1: high signal

• T2: high signal

• fat-suppressed sequences: shows fat suppression

Treatment and prognosis

They are a benign entity and no treatment is usually required in incidental asymptomatic cases. Resection can be offered to patients who are clinically symptomatic.

Differential diagnosis

On imaging, possible differential considerations include:

• inguinal hernias containing fat

• other inguinal canal / spermatic cord masses ³

  • liposarcoma

  • rhabdomyosarcoma

  • leiomyoma/leiomyosarcoma

  • schwannoma

• subcutaneous lipoma overlying the spermatic cord

See also

• lipoma

• paratesticular tumours