Undifferentiated Small Bowel Sarcoma With Distant Metastasis To Lung And Brain
Primary gastrointestinal (GI) sarcomas are uncommon tumors that account for 1% to 2% of all GI cancers.1,2 Of these sarcomas, about 33% occur in the small bowel.3 Because these malignancies are rare, few data have been collected regarding their clinical presentation, management, histologic variability, and prognosis. We report the case of a 42-year-old man who presented with primary small bowel sarcoma that metastasized to the right lower lobe of his lung and left temporal lobe of his brain. We discuss the implications of this case regarding the diagnosis, treatment, and classification of small bowel sarcomas.
A 42-year-old African-American man with a 2-week history of intermittent abdominal pain, nausea, and vomiting was admitted to an outside hospital. He reported a 4-year history of epigastric pain that improved with lansoprazole and became worse upon alcohol consumption. Laboratory tests revealed a hemoglobin level of 8.3 g/dL (normal, 13.6—17.2g /dL). After a computed tomography (CT) scan of his abdomen showed a small bowel obstruction due to intussusception, he was transferred to our hospital.
On admission, physical examination revealed a mildly distended abdomen with no palpable organomegaly or intra-abdominal masses. There were also no palpable masses on rectal examination. A stool specimen was guaiac-positive, however, and colonoscopy with biopsy and esophagogastroduodenoscopy were performed. The colonoscopy revealed diffuse mucosal edema, sigmoid colon hemorrhages, and a rectal polyp. A chest radiograph revealed a 5-cm lesion in the right lung. CT scans of the patient’s abdomen and thoracic cavity revealed intussusception and a 5-cm solid lesion in the right lower lobe of the lung (Figure 1).
Exploratory laparotomy was performed, revealing intussusception of the jejunum. A 3-cm palpable mass with multiple mesenteric lymphadenopathies was found after reducing the intussusception. Resection of the mass with the involved portion of the jejunum and mesentery and side-to-side stapled anastomoses were performed.
Upon pathological examination, the resected intestine lumen was filled with numerous detached, tan-grey, hemorrhagic soft tissue fragments. A hemorrhagic, 6.5 x 3.0 x 3.0-cm, pedunculated mass protruded from the intestinal wall and filled the lumen. The mass appeared to originate from the small bowel wall, which was retracted into the base of the mass. The cut surface of the tumor showed a central stalk of rubbery, tan-white tissue surrounded by dark red hemorrhagic tumor.
Histologically, the tumor was a high-grade pleomorphic sarcoma originating from the muscular small bowel wall. The tumor infiltrated the entire thickness of the bowel wall, and lymph-vascular invasion was present. The luminal surface of the tumor was ulcerated, and the large fragments that broke off intraluminally showed extensive necrosis. The tumor cells were pleomorphic, with both round and spindled cells present (Figure 2). There were 22 mitotic figures per 10 high-power fields. Eighteen mesenteric lymph nodes were examined and found to be negative for tumor. Immunohistochemical staining of the tumor was positive for vimentin and alpha-1-antichymotrypsin. Staining was negative for CD117 (c-Kit), Mart/Melan A, HMB45, S100, CD31, CD34, actin, desmin, HHF35, keratin, leukocyte common antigen, CD30, and KP-1.
After the patient recovered from the laparotomy, he underwent CT-guided biopsy of his right lower lobe lung lesion. Pathological review of the biopsy specimen revealed metastatic sarcoma. Subsequently, the patient reported right-sided weakness. A CT scan of his head was performed and revealed a left temporal lobe lesion (Figure 3). Because the lung lesion was diagnosed as metastatic sarcoma, the brain lesion also was thought to be a metastatic sarcoma. The patient underwent right lower lobectomy followed by whole-brain radiation therapy for the brain lesion. Despite these treatments, the patient’s condition deteriorated, and he died 6 months after his condition was diagnosed.
The small bowel accounts for 75% of the total length of the GI tract and more than 90% of the GI mucosal surface but is the site of only 1% to 2% of all primary GI malignancies.1,2 Sarcomas of the GI tract account for approximately 2% of all sarcomas occurring in adult patients, of which 35% arise in the small bowel. The annual incidence of small bowel sarcoma is 1.2 cases per million persons.3 Because small bowel sarcomas are exceedingly rare, the accumulated data regarding their clinical presentation, management, histologic variability, and prognosis are meager.
Recent studies on small bowel sarcoma have shown that the mean age of patients with this malignancy is 59.3 years (range, 8—94 years). There is a higher incidence of this malignancy among men and Caucasian patients. Most small bowel sarcomas occur in the jejunum and commonly present as GI bleeding and anemia.3 A majority of patients also experience abdominal pain and some weakness.4 There is no specific pattern of symptoms, however, associated with small bowel sarcomas.5 The patient in our case presented with abdominal pain, nausea, vomiting, anemia, and intestinal obstruction due to intussusception. To the best of our knowledge, a review of the literature showed no cases of small bowel intussusception due to an undifferentiated small bowel sarcoma. Although rare, some cases of small bowel intussusception due to small bowel leiomyosarcoma have been reported.4,6,7 Small bowel intussusception in adult patients is mostly caused by intraluminal ileal tumors, such as lipoma and leiomyoma, and is rarely caused by sarcomas of the jejunum.8
Because of the variability of symptoms associated with small bowel sarcomas, diagnosis can be difficult. Abdominal CT scans are reported to be the most useful diagnostic tool in determining tumor size and location.9 In contrast, endoscopy has been noted to be a relatively ineffective diagnostic tool.10 In our case, CT scans proved to be effective and endoscopic procedures ineffective at locating the tumor. The final diagnosis was confirmed by laparotomy and histopathology. Preoperative histologic diagnosis is not recommended in most cases because it does not change the surgical approach. A preoperative biopsy is unnecessary unless the lesion is unresectable and tissue is needed to determine an alternative approach.9
The overwhelming majority of small bowel sarcomas can be classified on the basis of their histologic features and immunophenotypic profile. In one study, most small bowel sarcomas were GI stromal tumors (GISTs).11 In another study of 1,441 small bowel sarcomas, 75% of the tumors were determined to be leiomyosarcoma, 6.9% were epithelioid leiomyosarcoma, 4.1% were Kaposi’s sarcoma, 4.0% were sarcoma-NOS (not otherwise specified), 2.8% were spindle cell sarcoma, 1.6% were fibrous histiocytoma, 1.0% were malignant neurolemmoma, and 4.5% were other sarcomas.3
GISTs characteristically express CD117 (c-Kit gene product), and most also stain positive for CD34 (human progenitor cell antigen).12 Immunoreactivity with antibodies to actin or desmin defines a tumor to be of muscular origin, whereas undifferentiated tumors exhibit only vimentin and CD34.12 Our patient’s tumor was not immunoreactive to CD117, CD34, desmin, actin, and several additional neural and vascular markers; therefore, it could not be classified by its cell of origin and was diagnosed as an undifferentiated sarcoma.
Surgical resection is the standard of care for small bowel sarcomas and usually involves resection of the tumor with wide margins along with the adjacent mesentery.1 This was the surgical method performed in the present case. Several studies have shown that complete resection of the primary sarcoma improves the 5-year patient survival rate.3 Prognosis is worse when the primary tumor has spread to distant sites, with distant spread conferring a 5-year survival rate of 6.5% versus 55% in cases where the tumor is localized.3 Our patient had a poor prognosis because his tumor had metastasized to his lungs and brain before surgery was performed.
Undifferentiated small bowel sarcomas are rare malignancies of the GI tract. As a result, data regarding the characteristics, treatment, and prognosis for these tumors are lacking. As more cases of these rare tumors are reported, the information learned can be applied toward improving patient care and survival.
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