Stromal cell tumors occur infrequently in children. They are rarely found in the anus. To our knowledge, they have never been reported in the rectum. We report a three year old child with a rectal stromal cell tumor. The patient presented with constipation, encopresis, abdominal distension, rectal bleeding, and urinary frequency. Although symptoms of encopresis are commonly encountered in children, this rare case report highlights the importance of a complete physical examination, including rectal examination, in these patients.
A three-year-old girl presented with a three-month history of abdominal distention and bloating. Her bowel movements were small and frequent, averaging nine times a day. She occasionally would pass small hard balls of stool, however, generally the stools were described as loose and containing blood and mucous. She had been toilet trained for 18 months but had developed encopresis a few weeks before her initial presentation. There was no associated fever, nausea, vomiting, weight loss, change in activity level, or hematemesis. She had had a significant increase in the frequency of urination to the point that the family had to identify the location of a bathroom at any place they visited. She had received several doses of magnesium citrate without relief of symptoms. She had otherwise been a healthy child who was developing appropriately.
Physical examination demonstrated a well-nourished and well-developed girl with a weight at the 50th percentile and a height at the 10th percentile. She had normal vital signs and did not appear pale. Her abdomen was significantly distended and hyper-resonant without masses, organomegaly, or ascites. Rectal examination revealed a palpable mass within 3 cm of the anal verge. The mass was rounded, firm, non-tender, and measured approximately 5 cm in diameter. There was a generous amount of blood and mucous in the rectal vault. Her neurologic exam was normal and she had normal deep tendon reflexes in the lower extremities. Examination of the back and spine was normal and no sacral dimples were seen.
Flexible sigmoidoscopy was performed, which confirmed the presence of a rectal mass. The mass was rounded and with some areas of friability, edema, and ulceration in the overlying mucosa (Fig. 1). Imaging studies were obtained to further localize the origin of the tumor. A pelvic ultrasound showed a heterogeneous vascular pelvic mass lying between the uterus and the rectum. A computerized tomographic scan of the abdomen and pelvis showed a mass anterior to the rectum and posterior aspect of the bladder (Fig. 2), which enhanced with contrast. No significant enlargement of the lymph nodes in the abdomen or pelvis was noted. An excessive amount of stools was partially obstructing the distal rectum. No metastatic lesions were seen on standard surveillance studies.
The following unrevealing laboratory studies were obtained: complete blood count, serum electrolytes, carcinoemberyonic antigen, alpha feto-protein, beta human chorionic gonadotropins, and urine vanillylmandelic acid. A bone marrow biopsy, aspirate, and bone scan were normal. These studies were obtained in consideration of the differential diagnosis of the rectal mass (Table 1) and to look for any metastatic lesions.
The patient underwent an exploratory laparotomy, and a transanal needle biopsy of the mass was obtained. A diverting colostomy was performed to relieve the advanced rectal obstruction. The tumor measured 5 × 3.4 × 3.0 cm with a solid finely trabeculated tan surface. At a later date, the tumor was completely resected and an anorectal pull-through (Soave) procedure was performed. The rest of the bowel, pelvis, retroperitoneum, and intra abdominal organs were carefully inspected for additional tumors or metastatic lesions and none were found.
On histologic examination, the tumor was a spindle cell neoplasm consistent with an undifferentiated gastrointestinal stromal tumor (Fig. 3). There was no striking mitotic activity. C-kit was non-reactive. However, CD34, which is used as a marker of undifferentiated gastrointestinal stromal cell tumors, was positive. After the nature of the tumor was identified, a full colonoscopic exam was performed and no additional masses or tumors were detected in the remainder of the colon.
Because of the difficulty in determining the malignant potential of this child's tumor, and lack of published guidelines for surveillance of this tumor in such a young patient, careful clinical follow-up was planned. The patient underwent CT scans of the abdomen, pelvis, and chest as well as full colonoscopies every six months for the first year and yearly thereafter. After two years, there is no evidence of local or metastatic disease.
Gastrointestinal stromal cell tumors (GIST) are considered visceral sarcomas arising from the gastrointestinal tract. There is evidence to suggest that they originate from the interstitial cells of Cajal (1,2). These tumors are not commonly encountered in children and most of the published experience is derived from adult patients. About half of the tumors arise in the stomach. Thirty five percent are found in the small intestine. Less than 10% are found in the rectum or anal canal (3). Metastatic lesions at the time of presentation are rare and local recurrence after resection is reported more frequently than metastases (4). In one report only 10% of patients were found to be free of disease after long-term follow up. Surgical resection of the tumor is the mainstay of therapy (5–7). Systemic chemotherapy or radiotherapy has not been proven to be effective, probably because of the slow cell turnover in the tumor. However, more recent reports on the use of STI571, an inhibitor of tyrosine kinase activity are promising (8,9). The peritoneal surface of the liver is the usual site for matastasis. Extra-abdominal metastasis is seen in the lungs and bones (4).
The differential diagnosis of rectal masses in children includes both benign and malignant lesions (Table 1). In the present case, the nature and site of origin of the tumor visualized on initial endoscopy was unclear. Therefore, an initial endoscopic biopsy of the tumor was deferred until further radiographic studies were obtained to help determine the extent and origin of the tumor. Computerized tomography can be helpful not only in localizing rectal tumors, but also to further characterize their vascularity (Fig. 2) and to detect metastatic lesions.
Rectal stromal tumors represent one in 2–3000 malignant rectal neoplasms (10,11). They are more common in males especially between the fifth and the seventh decades of life. At least 50% of these tumors are histologically malignant (12), and they often demonstrate unpredictable biologic behavior. Pain, bleeding, and alteration in bowel habit are the common presenting symptoms (13). Some authorities believe that all anorectal stromal cell neoplasms are potentially malignant. However, Haque et al. (14) in their review of 19 adult cases, found three patients without evidence of recurrence of neoplasm at least 5 years after resection. In general the prognosis is dependent on the tumor grade as reflected by the mitotic index (15). Tumors larger than 5 cm and with greater than five mitoses per high power field carry a poor prognosis and high mortality rate (12).
Our patient was three years of age at the time of diagnosis. To our knowledge, cases of rectal stromal-cell tumors have not been previously reported in this age group. Therefore, biologic behavior of this tumor can not be fully predicted. However, the fact that there was no striking mitotic activity is suggestive of a more benign course. She has been followed for 24 months with no evidence of recurrence or metastasis.
The presenting symptoms of encopresis and rectal bleeding are commonly encountered in children. However, in this particular case, a simple digital examination of the rectum was key in identifying the tumor and directing the future approach and management.
The authors thank Drs Wong, Mirkin and Laya for their input and assistance with the photographs.
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