INTRODUCTION
Urothelial carcinomas (UC) are malignant tumors that correspond to more than 90% of
the bladder tumors (1). The main sign of UC is hematuria, however with the routine
use of imaging exams, more patients are being diagnosed whilst asymptomatic. On ultrasonography
(US), UCs present as a focal bladder wall thickening and/or a polypoid lesion (2).
Nevertheless, these findings may be due to several other malignant and non-malignant
differential diagnoses, such as nephrogenic adenoma, inverted papilloma, leiomyoma,
amyloidosis, glandular cystitis, endometriosis, bladder xanthoma, among others (3–6).
Cystoscopy is the gold standard procedure to investigate patients with suspicion of
any bladder neoplasia.
Our objective is to report a case of Tamm-Hosrsfall protein deposit in the bladder
wall, mimicking a vesical UC.
CASE REPORT
A 51-year-old asymptomatic man, with no history of hematuria, underwent to a routine
US. The exam demonstrated a bladder with regular walls, except for an area of focal
thickening and a nodular lesion in the bladder floor, close to the right ureteral
meatus (Figure-1). Serum and urinary laboratory tests were normal.
Figure 1
A: US with an area of focal thickening in the bladder floor (arrow); B: The focal
thickening in the bladder floor is close to the ureteral meatus (arrow show the ureteric
jet in US doppler); C: Nodular lesion in the bladder floor, close to the focal thickening
(arrow).
Cystoscopy found three elevated lesions in the right lateral vesical wall, each one
with about 0.5cm, all of which with intact mucosa. Additionally, there was an ipsilateral
ulcerated peri-meatal lesion (Figure-2). All lesions were cold-cup biopsied and the
pathological analysis revealed deposition of an eosinophilic proteinaceous substance
throughout the mucosa and around the vessels. This was also associated with a mixed
inflammatory process at the lamina propria, without evidence of cellular atypia (Figures
3 and 4). The search for infectious agents and amyloid protein (red-congo) were negative.
The findings led to the diagnosis of Tamm-Horsfall protein deposition (THP). The patient
remained asymptomatic and had no complications following the procedure.
Figure 2
(cystoscopy) – A) right peri-meatal region, which is evidencing ulcerated lesion (thick
arrow) and lesions elevated with intact mucosa (narrow arrow); B) Image focused on
elevated lesions (thick arrow); C) image focused on ulcerated lesion.
Figure 3
Hematoxylin and Eosin (H&E) stain - Bladder biopsy: deposits of eosinofilic material
in the lamina propria (arrows).
Figure 4
Periodic Acid Schif (PAS) stain: eosinofilic material deposits strongly positive by
the PAS stain.
DISCUSSION
The THP is a high molecular weight glycoprotein synthesized in the ascending portion
of the Henle loop, and in the distal convoluted tubule. THP is abundant in normal
human urine. Its actual physiological function remains unknown, but there is a hypothesis
about a possible protective factor against urinary tract infections, lithogenesis,
and some nephropathies (7–9).
The etiology for THP deposit is still unclear, however it is most likely related to
mucosal changes, such as inflammation and necrosis (7–9).
A series of three patients with atypical THP mimichking tumor at the peri-pelvic and
peri-renal fat tissues has been reported. In addition to the initial bladder carcinoma
diagnostic hypothesis, renal pelvic neoplasia and urinary tuberculosis were also suspected
(10). Another report presented a patient with a ureteral lesion associated with hydronephrosis,
which suggested a tumor, but exactly like our case, histology favored THP deposition
(11).
A large study consisting of 247 bladder biopsies and 15 specimens of cystectomy identified
the presence of THP deposition in the bladder tissue in 18 cases (6.9%). The cystectomy
cases presented positive biopsies for THP deposition in 60% of the patients, higher
than isolated biopsies (3.6%). The author describes a typical pathological finding
characterized by whitish masses with discrete eosinophilic deposition (12). However,
our patient, beyond the THP deposits mimicking a bladder tumor, did not present any
other bladder pathology or symptoms.
There are reports that have identified association between bladder wall THP deposition
and interstitial cystitis (13, 14). Additionally, patients with interstitial cystitis
have been reported to have changes in THP when compared to control groups.
Our case demonstrates that THP deposition in the bladder may be one of the differential
diagnoses for bladder lesions, mainly when the lesion does not have the usual papillary
aspect and appears to be in a sub-urothelial layer.