Bladder leiomyoma is the most common benign bladder tumor, arising from the smooth muscle layer (detrusor muscle) of the bladder wall, accounting for 0.4-0.5% of all bladder tumors. It is more common in women than men (F:M = 3:1) and most frequently diagnosed between ages 30-50. Most patients are asymptomatic and the lesion is found incidentally. Symptomatic cases may present with obstructive symptoms (urinary retention, weak stream), irritative symptoms (frequency, dysuria), or hematuria. The tumor is well-defined, round-to-oval, homogeneous, and may show endovesical (intraluminal, 63%), intramural (7%), or extravesical (30%) growth pattern. Malignant transformation is extremely rare. Treatment is surgical excision, and recurrence is very rare.
Age Range
30-60
Peak Age
44
Gender
Female predominant
Prevalence
Rare
Bladder leiomyoma arises from benign neoplastic proliferation of smooth muscle cells of the detrusor muscle. Smooth muscle cells proliferate in interlacing bundles and grow by compressing surrounding tissue — without infiltration. This benign growth pattern forms the basis of the lesion's well-defined, encapsulated appearance. As the lesion contains homogeneous smooth muscle tissue, it shows characteristic low signal intensity on T2 MRI — this results from the short T2 relaxation time of smooth muscle fibers (similar to uterine leiomyomas). Enhancement is homogeneous and moderate because the tumor has organized capillary architecture but lacks the disorganized neovascularity of malignant tumors. Diffusion restriction is not prominent because cells are in organized arrangement with adequate intercellular space — this feature is important for differentiating from malignant tumors. In endovesical growth pattern, the tumor lifts the mucosa and protrudes into the lumen — the mucosal surface remains intact, and this feature is critical for distinguishing from urothelial carcinoma.
The bladder mass shows homogeneous low signal intensity on T2W MRI — identical to the T2 signal of uterine leiomyomas. This finding is pathognomonic for benign smooth muscle-origin tumor and reliably distinguishes from other bladder tumors (urothelial carcinoma: intermediate signal, leiomyosarcoma: heterogeneous signal). The triad of homogeneous low T2 signal + smooth margins + no DWI restriction establishes leiomyoma diagnosis with high confidence.
Well-defined, round-to-oval, homogeneous low signal intensity mass in the bladder wall or lumen on T2W MRI. Signal intensity is similar to or slightly lower than normal detrusor muscle. Homogeneous structure is preserved — necrosis, hemorrhage, or cystic degeneration are very rare (unless >5 cm). The lesion margin is sharply defined and there is no perivesical fat infiltration.
Report Sentence
A well-defined, homogeneous low signal intensity mass measuring approximately ___ mm is seen in the ___ wall/lumen of the bladder on T2W MRI, consistent with leiomyoma.
Leiomyoma does not show significant diffusion restriction on DWI. Iso- or mildly hypointense signal is seen. ADC values remain normal or mildly low (due to smooth muscle tissue). This finding is critically important for differentiation from malignant bladder tumors (urothelial carcinoma, leiomyosarcoma) — malignant tumors show marked diffusion restriction.
Report Sentence
The bladder mass does not show significant diffusion restriction on DWI (ADC: normal/mildly low), consistent with benign lesion (leiomyoma).
Leiomyoma shows homogeneous and moderate enhancement on contrast-enhanced MRI. Enhancement is uniform throughout the mass — no necrotic, non-enhancing areas. Enhancement degree is similar to normal detrusor muscle. This homogeneous pattern is distinguishing from heterogeneous enhancement in malignant tumors.
Report Sentence
The bladder mass shows homogeneous and moderate enhancement on contrast-enhanced MRI with no necrotic areas or heterogeneous enhancement; consistent with leiomyoma.
Well-defined, homogeneous, soft tissue density (40-60 HU) mass on the bladder wall on CT. Shows homogeneous enhancement on portal venous phase. Calcification is very rare. No perivesical fat infiltration. Mass-bladder wall interface is sharp and smooth.
Report Sentence
A well-defined, homogeneously enhancing soft tissue mass measuring approximately ___ mm is seen on the ___ wall of the bladder on CT; benign lesion (leiomyoma) is considered and MRI characterization is recommended.
Well-defined, oval, homogeneous hypoechoic mass on the bladder wall on US. Echogenicity is similar to or slightly lower than normal bladder wall. Internal echoes are homogeneous — no areas of cystic degeneration or necrosis. Smooth surface is covered by intact mucosa. Color Doppler may demonstrate organized vascularity within the mass.
Report Sentence
A well-defined, homogeneous hypoechoic mass measuring approximately ___ mm is seen on the ___ wall of the bladder on US; leiomyoma is considered.
Smooth-surfaced, round-to-oval filling defect within the bladder lumen on excretory phase. Unlike urothelial carcinoma, the surface is smooth — no papillary or irregular architecture. Mass is surrounded by opacified urine and shows homogeneous soft tissue density.
Report Sentence
A smooth-surfaced, round-to-oval filling defect is seen within the bladder lumen on excretory phase; submucosal benign lesion (leiomyoma) is considered.
Criteria
Tumor grows toward the bladder lumen. Most common type (63%). Lifts mucosa to form intraluminal mass.
Distinct Features
Intraluminal well-defined mass on CT/MRI, intact mucosa, filling defect visible on excretory phase. Obstructive symptoms more common.
Criteria
Tumor grows outward from bladder wall. Second most common type (30%). May present as pelvic mass.
Distinct Features
Mass connected to bladder wall but outside the lumen. May compress adjacent structures. Pelvic MRI can demonstrate bladder origin.
Criteria
Tumor remains within the bladder wall. Rarest type (7%). May present as wall thickening.
Distinct Features
May appear as focal wall thickening, well-defined, T2 low signal. DWI and enhancement pattern critical for differentiation from leiomyosarcoma on MRI.
Distinguishing Feature
Urothelial carcinoma shows intermediate T2 signal, heterogeneous enhancement, marked DWI restriction. Leiomyoma shows T2 low signal, homogeneous enhancement, no DWI restriction. Papillary/irregular surface in urothelial carcinoma, smooth surface in leiomyoma.
Distinguishing Feature
Paraganglioma shows very high T2 signal (light bulb sign), very prominent arterial enhancement, DWI restriction. Catecholamine symptoms during micturition (hypertension, palpitations) are pathognomonic. Leiomyoma has low T2 signal and different symptom profile.
Distinguishing Feature
Leiomyosarcoma shows heterogeneous T2 signal (necrosis, hemorrhage), irregular margins, marked DWI restriction, and rapid growth. Leiomyoma shows homogeneous T2 low signal, smooth margins, no DWI restriction.
Distinguishing Feature
Inverted papilloma appears as smooth-surfaced intraluminal mass but shows intermediate T2 signal (different from low T2 signal of leiomyoma). Enhancement may be more prominent. Histological confirmation may be needed.
Urgency
routineManagement
surgicalBiopsy
Not NeededFollow-up
6-monthBladder leiomyoma is a benign tumor with extremely low risk of malignant transformation. If MRI findings are typical (homogeneous T2 low signal, no DWI restriction, smooth margins), biopsy may not be needed and follow-up may be sufficient. In symptomatic cases, surgical excision (transurethral resection or partial cystectomy) is curative. Recurrence is very rare (<1%). Small asymptomatic lesions can be followed with observation.
Bladder leiomyoma is a benign tumor with no risk of malignant transformation. Small lesions can be followed. TUR or partial cystectomy is performed for symptomatic or large lesions. Prognosis is excellent — recurrence is rare, no mortality. Differential diagnosis with leiomyosarcoma is important: biopsy is needed if necrosis, heterogeneity, or rapid growth is present.