2015, Volume 31, Number 1, Page(s) 064-067
Incidental Bladder Lipoma: A Case Report and Review of the Literature
José-Fernando VAL-BERNAL1, Ainara AZUETA1, Roberto BALLESTERO2, Javier FUENTES2, Alejandro FERNANDEZ-FLÓREZ3
1Department of Anatomical Pathology, University of Cantabria and IDIVAL, Marqués de Valdecilla University Hospital, SANTANDER, SPAIN
2Department of Urology Service, University of Cantabria and IDIVAL, Marqués de Valdecilla University Hospital, SANTANDER, SPAIN
3Department of Diagnostic Radiology Service, University of Cantabria and IDIVAL, Marqués de Valdecilla University SANTANDER, SPAIN
Keywords: Lipoma, Urinary bladder neoplasms
Conventional lipoma is the most common benign mesenchymal
neoplasm in adults. However, bladder lipoma is a rare tumor. We
report an incidental 0.5-cm, mucosal, bladder lipoma in a 75-year-old
man, successfully treated with endoscopic excision. The tumor
was found during the extension study of a high-grade urothelial
carcinoma of the renal pelvis. A review of the published cases,
including the present report, yielded a total of 16. Conclusions on this
review are presented. The case is being reported because its rarity and
to highlight the importance of complete workup to clarify associated
disorders that may suggest extension of a malignant process.
Conventional lipomas are the most common benign
mesenchymal neoplasms in adults. They occur mostly in
persons after the age of 40 with a male predominance1
Most lipomas are superficial, and deep or visceral lipomas
are uncommon. These deep or visceral lipomas are often
discovered at a late stage of development and consequently
tend to be larger than superficial lipomas.
The most frequent benign mesenchymal tumor in the
urinary bladder is leiomyoma. Bladder lipomas are rare
tumors. As far as we are aware, only 15 cases of this neoplasm
have been documented2-16. We report herein a small
mucosal lipoma of the bladder incidentally discovered
during cystoscopy. Besides, a review of the literature on this
subject is presented.
A 75-year-old man was referred to the urology service
for surgical treatment of a 3-cm, high-grade urothelial carcinoma of the left renal pelvis. Past medical history
was insignificant. A radical left nephroureterectomy
was performed. Computerized tomography (CT) scan
demonstrated a 0.3x0.3 cm round, fat density filling defect
in the bladder dome (Figure 1A,B
). During cystoscopic
examination, a smooth, yellow-colored, well-circumscribed,
submucosal polyp measuring 0.7x0.6x0.4 cm within
the dome of the bladder was detected. Transurethral
resection of the entire lesion was performed and sent for
Click Here to Zoom
|Figure 1: Contrast-enhanced
tomography (CT). A tiny
hypodense lesion in the inner
right surface of the bladder
dome can be seen. It is a
0.3 cm tumor with negative
Hounsfield values (-22 units)
consistent with the fatty nature
of the lesion demonstrated in
the white circle in (A) axial
CT image in portal phase,
and (B) coronal multiplanar
reconstruction in excretory
A B phase scan image.
Microscopic study demonstrated a well-circumscribed,
ovoid, expansile nodule of mature adipose tissue located
within the lamina propria of the mucosa layer without any
evidence of malignancy or bladder wall invasion (Figure 2).
The lesion was covered by a thin rim of urothelial mucosa
(Figure 3). The maximum diameter of the fat lesion was 0.5
Click Here to Zoom
|Figure 2: Histopathology of the bladder lipoma. Panoramic
microscopic view of the specimen showing a well-circumscribed,
rounded neoplasm composed of mature fat cells located in the
lamina propria (H&E; x16).
Click Here to Zoom
|Figure 3: Higher power view of the specimen. A thin rim
of urothelial mucosa is covering the neoplasm consisting of
univacuolar adipocytes without atypia (H&E; x25).
The patient had an uneventful recovery during the
postoperative follow-up period.
Lipomas are usually asymptomatic, slow-growing, nontender,
round masses with soft consistency. Deep visceral
lipomas may cause a variety of symptoms depending of
their site and size.
Bladder lipoma is rare. A review of published cases of
bladder lipoma, including the present report, yielded a total
of 16 (Table I). The mean age of these patients at presentation
was 56.2 years (SD, 12.4; range, 32-75 years). Nine (56.2%)
patients were male. The lesion can show endophytic or
exophytic, and sessile or pedunculated growth. All tumors
had a yellowish color.
Most tumors were endophytic in mucosa or submucosa.
Attenuation coefficient of these lesions in Hounsfield units
indicates lipomatous tissue by CT. Cystoscopy findings
were very suggestive. In these cases transurethral resection
was performed to achieve histologic confirmation. These
tumors were small and most of them (59.1%) measured
less than 2 cm. Exophytic neoplasms can be very large2,13 and they may present as a retroperitoneal mass13.
Lipomas were located in every site of the bladder and most
of them were covered by urothelial mucosa. Seven (36.8%)
cases were located in the posterior wall and 5 (26.3%) in
the fundus or dome. They may present with hematuria,
urinary frequency, nocturia, urinary tract infection, or as
a retroperitoneal mass. The most common presentation
(56.2%) is asymptomatic gross or microscopic hematuria.
The bleeding can be attributed to excoriations of the
mucosa over the lipoma. The neoplasm was incidentally
observed in 3 (18.7%) of cases. In 4 (25%) cases the patients
had multiple lipomas.
Microscopically, lipomas were well-circumscribed, expansile
neoplasms composed of mature adipose tissue. The
voluminous tumor described by Sederl was a fibrolipoma2.
Differential diagnosis of bladder lipoma includes welldifferentiated
liposarcoma, pelvic lipomatosis, and urachal
fibrolipoma. Well-differentiated liposarcoma shows marked
variation in adipocyte size, nuclear hyperchromasia, scattered lipoblasts, and bizarre multinucleated stromal
cells. Pelvic lipomatosis is characterized by massive
overgrowth of mature adipose tissue in the perivesical and
perirectal portions of the pelvic retroperitoneum. The fat
tissue causes external compression of the lower urinary tract
and rectosigmoid colon. The patients complain of perineal
or lower abdominal pain, increased urinary frequency,
hematuria and constipation. The fatty growth is diffuse
rather than nodular17. The urachus, which extends from
the umbilicus to the apex of the bladder, involutes shortly
after birth becoming a fibrous cord called the median
umbilical ligament. Though rarely, a calcified fibrolipoma
may appear in this structure18. Bladder lipomas behaved
as benign tumors with no recurrences.
In conclusion, lipoma is a rare finding within the bladder
wall. The most common presentation is asymptomatic
hematuria. The tumor may be incidentally found during
the clinical search for another process. Most tumors were
endophytic, yellowish, located in mucosa/submucosa,
and measured less than 2 cm. CT density and cystoscopic
observation suggest benign adipose tissue. All reported cases
behaved as benign lesions and did not show recurrences.
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