Figure 1
Transabdominal ultrasound
An intrapelvic mass seen with mixed hypo- and hyperechogenic components.
Clinical History
A patient presented with10-year history of atypical dull pain in the lower abdomen. He also complained of recent aggravation of pain and radiculopathy in the right leg.
Imaging Findings
The patient presented with an atypical 10-year history of dull pain in the lower abdomen. About 4 months prior to presentation, the pain worsened and became associated with pain and radiculopathy in
the right leg. There was nothing of note in the previous medical history. The results of routine laboratory tests and urinalysis were normal. A neurological examination of the patient revealed
fasciculation potentials and slowed denervation potentials of the right lower extremity.
An abdominal US examination was performed. An intrapelvic mass (7 cm x 8 cm x 11cm) was found with a heterogeneous composition. A CT scan taken confirmed the presence of an infraperitoneal,
presacral and retrovesical mass, which was indistinguishable from the right seminal vesicle. The lesion compressed the urinary bladder against the anterior abdominal wall, displaced the sigmoid
colon posterolaterally to the left and the prostate inferiorly. There were no calcifications. The fat planes between the lesion and the adjacent organs were preserved. There were no enlarged lymph
nodes. On MRI, the lesion displayed mixed low and high signal intensities on T1-weighted images and T2-weighted images, suggesting solid, cystic, and haemorrhagic or necrotic areas. After
intravenous contrast medium administration, there was moderate and heterogeneous enhancement of the content of the mass, which was enveloped by a thick enhancing wall.
These CT and MRI findings were strongly suggestive for an intrapelvic tumour with cystic degeneration, infiltrating or originating from the right seminal vesicle. A tumour of neurogenic origin
(schwannoma) or seminal vesicle cystadenoma was suggested.
Discussion
A surgery was performed because of increasing subjective complaints. At surgery, it was noticed that the tumour was adherent to the right L5 and S1 nerves and the demarcation between the tumour and
the right seminal vesicle was indistinct. The tumour and the right seminal vesicle were resected completely.
A histopathological examination revealed a partially encapsulated tumour with cystically dilated spaces admixed with spindle-shaped cells infiltrating the right seminal vesicle. On
immunohistochemical staining, most of those spindle cells showed a strong expression of S-100 protein within the cytoplasm. This protein is a highly acidic protein which is completely soluble in
solutions of concentrated ammonium sulphate at neutral pH. This is almost an exclusive feature of a schwannoma. Schwannomas consist of mixed compact cellular regions with varying degrees of nuclear
atypia (Antoni type A tissue) and loose hypocellular or cystic regions (Antoni type B tissue). In this case, the type B tissue dominates the histological picture and therefore "ancient" or
"degenerated" is added.
A problem in this case was to clarify whether the mass originated from the seminal vesicle or invaded the seminal vesicle. On surgery, the origin seemed most likely to be at the nerve roots L5 and
S1 with compression of the right seminal vesicle. This was supported by the fact that most of the spindle cells were clustered near the nerves. In addition, nerve sheath schwannomas are far more
frequent than schwannoma of the seminal vesicle. Furthermore, after surgery there was a temporary (5 months) motor loss in L5 and sensible loss in the S1 region of the right leg, probably due to
resection of the branching fascicles from the underlying nerves.
Most primary tumours of the seminal vesicles are benign, including cystadenoma, fibroma, leiomyoma and schwannoma. Primary malignant tumours include adenocarcinoma, leiomyosarcoma and
haemangiosarcoma. More often, however, the seminal vesicles are involved by a carcinoma from the bladder, the rectum, the prostate or lymphoma.
The CT features of schwannoma include a well-delineated tumour, with smooth outlines and variable densities, ranging from a density close to water to that of a muscle. Contrast enhancement in
various degrees can be expected in virtually all schwannomas. The advantage of MRI is that it provides better tissue contrast resolution as well as the evaluation of the lesion in different spatial
planes. The heterogeneity on T2-weighted MRI reflects the histological composition, with the intermediate signal intensities representing Antoni type A tissue and the high-intensity signal most
likely representing Antoni type B tissue. Central necrosis and haemorrhage may also be present. Calcifications are rare.
Schwannomas generally become symptomatic during the fourth or fifth decade of life and males are almost equally affected as females. They usually become symptomatic due to the mass effect, causing
pain and radiculopathy. Most often, schwannomas are solitary lesions; multiple tumours are commonly associated with type 2 neurofibromatosis. They can occur intracranially, intraspinally or
peripherally. They are considered to be benign tumours. Malignant schwannomas tend to have an aggressive behaviour with infiltration of the surrounding structures.
In the present case, the benign nature is further supported by the clinical course: the patient showed complete recovery 14 months after surgery with no evidence of recurrence.
Differential Diagnosis List
Ancient schwannoma of the right L5 and S1 nerves, with involvement of the right seminal vesicle.
Final Diagnosis
Ancient schwannoma of the right L5 and S1 nerves, with involvement of the right seminal vesicle.
References
[1]
Hide IG, Baudouin CJ, Murray SA, Malcolm AJ.
Giant ancient schwannoma of the pelvis.
Skeletal Radiol. 2000 Sep;29(9):538-42. (PMID: 11000301)
[2]
Gominak SC, Ochoa JL.
Sciatic schwannoma of the thigh causing foot pain mimicking plantar neuropathy.
Muscle Nerve. 1998 Apr;21(4):528-30. (PMID: 9533788)
[3]
Nasu K, Arima K, Yoshimatsu J, Miyakawa I.
CT and MRI findings in a case of pelvic schwannoma.
Gynecol Obstet Invest. 1998 Aug;46(2):142-4. (PMID: 9701697)
Case information
| URL: | https://www.eurorad.org/case/1964 |
| DOI: | 10.1594/EURORAD/CASE.1964 |
| ISSN: | 1563-4086 |
Figure 2
Transrectal ultrasound
The same intrapelvic mass seen with mixed hypo- and hyperechogenic components.
Figure 3
Abdominale CT
A presacral well-demarcated mass (7 cm x 8 cm x 11 cm) with a thick wall, solid and cystic components and displaying a heterogeneous enhancement.
The same mass, located infraperitoneal, presacral and retrovesical, superior to the prostate and not distinguishable from the right seminal vesicle. There is even displacement from the bladder against the anterior abdominal wall and the sigmoid colon posterolateral to the left.
Figure 4
Abdominal MRI
Axial T1-weighted image after gadolinium and fat suppression. (See CT results at the same level in Figure 6a.)
Axial T2-weighted image at the same level as shown in Fig. 4a.
Axial T1-weighted image after gadolinium and fat suppression at a lower level when compared to that shown in Figs. 4a and 4b.
Coronal T1-weighted image after gadolinium and fat suppression.
Sagittal T2-weighted image.
Figure 5
Abdominal MRI
T2-weighted imaging in the sagittal plane.
Figure 6
Abdominal CT
The same mass, located infraperitoneal, presacral and retrovesical, superior to the prostate and not distinguishable from the right seminal vesicle. There is even displacement from the bladder against the anterior abdominal wall and the sigmoid colon posterolaterally to the left. At the same level as seen in the MR image, Fig. 4a.
Transabdominal ultrasound
An intrapelvic mass seen with mixed hypo- and hyperechogenic components.
Transrectal ultrasound
The same intrapelvic mass seen with mixed hypo- and hyperechogenic components.
Abdominale CT
A presacral well-demarcated mass (7 cm x 8 cm x 11 cm) with a thick wall, solid and cystic components and displaying a heterogeneous enhancement.
The same mass, located infraperitoneal, presacral and retrovesical, superior to the prostate and not distinguishable from the right seminal vesicle. There is even displacement from the bladder against the anterior abdominal wall and the sigmoid colon posterolateral to the left.
Abdominal MRI
Axial T1-weighted image after gadolinium and fat suppression. (See CT results at the same level in Figure 6a.)
Axial T2-weighted image at the same level as shown in Fig. 4a.
Axial T1-weighted image after gadolinium and fat suppression at a lower level when compared to that shown in Figs. 4a and 4b.
Coronal T1-weighted image after gadolinium and fat suppression.
Sagittal T2-weighted image.
Abdominal MRI
T2-weighted imaging in the sagittal plane.
Abdominal CT
The same mass, located infraperitoneal, presacral and retrovesical, superior to the prostate and not distinguishable from the right seminal vesicle. There is even displacement from the bladder against the anterior abdominal wall and the sigmoid colon posterolaterally to the left. At the same level as seen in the MR image, Fig. 4a.