Solitary malignant schwannoma - (A case report)SD Shetty1, AC Pinto1, Sudha Y Sane2, RA Bhalerao1
1 Department of Surgery, Seth G. S. Medical College and K.E.M. Hospital, Parel, Bombay-403 012, India
2 Department of Pathology, Seth G. S. Medical College and K.E.M. Hospital, Parel, Bombay-403 012, India
A case of retroperitoneal malignant schwannoma is reported. A brief review of the literature is given.
Schwannomas are essentially benign tumors arising from Schwann cells of neurectodermal origin. In 1935, Stout  first interpreted this as fibrosarcoma, though he , revised his opinion in 1949 after observing the outgrowth of Schwann cells in vitro from such tumors . 
A 15 year old boy was admitted with history of vehicular accident. There was history of fall on the abdomen. Detailed examination on admission was as follows: Pulse was 92/min. Blood pressure was 120/80 mm of Hg. Patient was conscious. Abdominal examination revealed tenderness and guarding over the left subcostal region anteriorly. There was a firm, tender lump moving minimally with respiration over the left hypochondrium, the top of which could not be reached. There was no free fluid in the abdomen. Chest was normal. No other extenrnal injuries were noted. Abdominal paracentesis was negative. Hamoglobin at the time of admission was 8.5 gm% and after 12 hours it was the same. The cardiovascular parameters were the same after 12 hours. A diagnosis of splenic tear with hematoma was made in view of the physical signs. The patient was treated conservatively because the general condition was good and the cardiovascular status was maintained. A possibility of a previous lump was kept in mind but the patient refused any such history on admission. After 48 hours the tenderness and guarding under the left costal margins subsided and the top of the lump could be reached. After reassessment a diagnosis of a retroperitoneal tumor of the nature of fibrosarcoma was made. The patient admited that he had sought medical aid for the lump 2 months prior to the admission.
The patient was subjected to the following investigations:
(i) Plain X-ray of the abdomen was no mal
(ii) lntravenous pyelography showed hydronephrotic changes of the left kidney and the left ureter was displaced laterally. The right kidney was normal.
(iii) Barium enema showed displacement of the descending colon on to the left side.
(iv) Aortogram showed narrowing of the lower part of the aorta and slight shift to the right side. The inferior mesenteric selective arteriogram showed stretching of that artery and the left upper colic artery (See [Figure 1] on page 182B). The tumor was supplied by a branch from the inferior mesenteric artery.
(iv) Other routine investigations were within normal limits.
After the investigations the patient was taken up for exploration with a left paramedian incision. The colon was reflected on to the right side. There was a firm tumor near the lower pole of the left kidney, 10 cm in diameter, and well encapsulated except near its upper part where it was involving the hilum of the left kidney (see [Figure 2], on page 182B). The aorta was displaced to the right side. The growth could not be separated from the renal hilum, hence along with the growth the left kidney was also removed. The para-aortic lymph nodes were not enlarged. The patient had an uneventful postoperative recovery.
Section showed a well circumscribed tumor composed of spindle cells arranged in parallel rows showing nuclear palisading at places. Densely cellular areas were seen alternating with loose tissue. The nuclei were hyperchromatic and pleomorphic with areas of necrosis and hemorrhage, suggestive of malignant schwannoma (see [Figure 3], on page 182B).
Schwannomas are tumors arising from the neurilemmal sheath, common in all ages, without obvious preference for either sex.  Most patients are 40 years old and their lesions ordinarily are solitary.  Rarely schwannomas may be congenital.  In a small proportion of cases obvious stigmata of Von Recklinghausen's disease are accompanied. ,
Dasgupta and Brasfield,  after a review of 232 cases of malignant schwannoma gave the following incidence. Head and neck-8%, upper extremities-30% trunk-16%, lower extremities-38% and other various sites-8%. They had only four cases of retroperitoneal schwannomas. Ghosh et al  also report a high incidence in the extremities.
Patients mainly present with a swelling in the affected region. It is quite often solitary. In a series of 115 patients, Ghosh et al  had 30% incidence of features of Von Recklinghausen's disease. Often the lesions are pigmented. Maher and Goodman  reported a case of retroperitoneal malignant schwannoma with chylous ascites.
Macroscopically they are fusiform swellings sometimes encapsulated initially lying within the perineurium. Rounded, ovoid, occasionally bosselated growths of firm or cystic and fluctuant character are seen. The feature that distinguishes these from neurofibroma is that the latter never undergoes degenerative cystic changes.  Cut section shows grey white in color, whorled with areas of hemorrhage.  Microscopic appearance shows spindle cell growth pattern with cells arranged in tight wavy or interlacing bundles. The nuclei are plump, ovoid or vesicular. One mitosis per high power field is seen. In bizarre pleomorphic type the mitoses are multiple and also have connective tissue stroma. The cells are cuboidal forming an epitheloid pattern. On occasion osteoid and cartilage formation has been noted by some workers . 
The tumor spreads only by local invasion. Lymph node involvement is not seen. ,
Radical excision based on location, shape, size and local spread is the treatment of choice. , The tumor including its bed, any attached muscle, bone, fascia or blood vessel should be resected through a normal segment. If the tumor is over the extremity a major amputation should be done to prevent local recurrence.
Incidence of local recurrence is 46.2%; Patients can be treated by initial radiotherapy and later on by wide excision.
The 5-year survival rate of operable group is 50% Ghosh et al  reported a 5-year survival rate of 65.7%. Many patients treated originally by radiation required subsequent excision. Radical excision seems to be the best method of control. Malignant schwannoma when associated with Von Recklinghausen's disease has 30% five-year survival rate.  Prognosis of our case cannot be predicted as paravertebral schwannomas are known to have a poor prognosis. 
The authors are thankful to Dr. C. K. Desphande, M.D., F.R.C. Path. (Lond.), Dean, Seth G.S. Medical College and K.E.M. Hospital, Bombay, for permitting us to publish the hospital data.
[Figure 1], [Figure 2], [Figure 3]