AJR 2001; 177:652
© American Roentgen Ray Society
Radiologic-Pathologic Conferences of the
University of Texas
M. D. Anderson Cancer Center |
Benign Schwannoma in the Porta Hepatis
Haesun Choi1,
Gary Whitman1,
Jae Ro2 and
Chusilp Charnsangavej3
1
Division of Diagnostic Radiology, The University of Texas M. D. Anderson
Cancer Center, 1515 Holcombe Blvd., Box 057, Houston, TX 77030.
2
Department of Pathology, The University of Texas M. D. Anderson Cancer Center,
Houston, TX 77030.
3
Division of Diagnostic Imaging, The University of Texas M. D. Anderson Cancer
Center, Houston, TX 77030.
Received January 16, 2001;
accepted after revision March 1, 2001.
From the weekly radiologic—pathologic correlation conferences
conducted by Gary J. Whitman.
Address correspondence to H. Choi.
Introduction
A 37-year-old asymptomatic man was referred for evaluation of a mass in the
porta hepatis found incidentally during a workup performed after the patient's
hepatitis serology test had shown positive results. Sonograms showed a
well-defined, 5-cm complex mass at the porta hepatis with a large hyperechoic
solid component (Fig. 1A). MR
imaging revealed a heterogeneous mass consisting of cystic and gradually
enhancing solid areas. CT scans showed the solid component enhancing gradually
during a 10-min period (Figs.
1B and
1C). At surgery, the mass was
found to be encasing the right hepatic artery and appeared to be arising from
it. The mass was otherwise well separated from adjacent solid organs, bile
ducts, and other major vessels. Gross cystic degenerative changes with areas
of calcification and prominent vessels were present in the solid mass.
Microscopically, the mass consisted of bundles of spindle cells with
hypercellular and hypocellular areas (Fig.
1D). Final pathologic diagnosis was a benign schwannoma.
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Fig. 1D. —Benign schwannoma in porta hepatis in 37-year-old man.
Photomicrograph reveals bundles of spindle cells (arrow) with
hypercellular (Antoni type A) and hypocellular (Antoni type B) areas. (H and
E, x200)
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Benign schwannomas, also referred to as neurilemomas, neurinomas, and
perineural fibroblastomas, are encapsulated nerve sheath tumors. They are
usually slow-growing and may occur at any age, although they are most commonly
seen in patients who are between the ages of 30 and 60
[1]. Slightly more common in
women than in men, schwannomas occur most frequently in the head, neck, and
flexor surfaces of the upper and lower extremities. Deep-seated tumors may
occur in the mediastinum, rarely in the retroperitoneum, and very rarely in
the mesentery [1,
2]. To our knowledge,
schwannoma in the porta hepatis has not been previously reported. Symptoms and
signs vary depending on the anatomic site and size of the neoplasm; however,
most schwannomas present as an asymptomatic or painless mass
[1].
Histologically, schwannomas are encapsulated tumors that arise within the
nerve sheaths and consist of a highly ordered cellular component (Antoni type
A area) and a loose myxoid component (Antoni type B area). Occasionally they
may degenerate and become cystic because of either hemorrhage or necrosis.
Dystrophic calcification and xanthomatous degeneration can occur. Schwannomas
can also be quite hypervascular. The presence of encapsulation, the two types
of Antoni areas, and uniformly intense immunostaining for S-100 protein
distinguish schwannomas from neurofibromas
[1].
The radiologic appearance of schwannomas varies depending on the
distribution of the different histologies (Antoni A and Antoni B areas) and
the degrees or types of degeneration. In general, schwannomas are well defined
with smooth margins and are relatively heterogeneous on CT and MR images
[3,
4]. They are usually
hypointense on T1-weighted images and reveal increased signal intensity on
T2-weighted images. They may be cystic, hemorrhagic, or calcified. A target
appearance with a hyperintense rim attributable to peripheral myxomatous
tissue has been described as a useful diagnostic finding on MR images of
benign nerve sheath tumors [4].
Central enhancement related to hypercellular Antoni A areas has also been
described on CT and MR images
[2]. Prolonged delayed
enhancement has been reported
[5].
Treatment of benign schwannomas is simple excision. Recurrent disease is
extremely rare even after partial resection. Incomplete excision is warranted
in patients in whom permanent nerve damage is likely to occur
[1].
References
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Introduction
References
