Submucosal tumors (SMTs) in the digestive tract include neoplastic and non-neoplastic
lesions. Attempts have been made to grade the severity of mesenchymal tumors pathologically,
using various criteria for malignancy, such as tumor size, cellularity, mitotic index,
and DNA content [1]. We recently treated a patient with a malignant gastrointestinal stromal tumor (GIST),
and describe an interesting diagnostic pitfall which arose from the use of endoscopic
ultrasonography for follow-up examination after the operation.
A 67-year-old woman was referred to our hospital for detailed investigation of an
SMT of the upper stomach. Ultrasonography showed that the tumor was 80 mm in diameter
and had an internal echo pattern of mixed irregular type. These findings matched positive
signs of malignancy, which had met the diagnostic criteria for malignant SMT. A proximal
gastrectomy was performed. The surgically resected tumor was 92 × 80 × 65 mm in diameter,
and the surgical margin was free of tumor cells. The cellularity of the tumor was
high, and a mitotic index of 1-3/1HPF was noted. Immunohistochemical staining gave
results of s-100 protein-negative, actin-negative, c-kit-positive, and CD34-positive.
Based on these pathological findings, the tumor was diagnosed as a GIST, uncommitted
type or Cajal cell type, with low-grade malignancy. At 9 months after gastrectomy,
follow-up endoscopic examination revealed two SMTs in the stomach remnant, which were
15 mm and 20 mm in diameter (Figure [1]). With regard to the larger tumor, endoscopic ultrasonograpy revealed an echolucent
submucosal mass arising from the fourth echolayer, the muscularis propria of the gastric
wall. The tumor expanded with notched sign (Figure [2]). These findings suggested that the lesions were recurrent or multiple aberrant
GISTs with malignant potential. A total gastrectomy was performed. Histological examintaion
showed that both of the resected tumors were foreign body granulomas composed of suture
silk.
Figure 1 Endoscopic finding of two submucosal tumors in the remnant stomach
Figure 2 Ultrasonography demonstrated a mixed irregular echo pattern
Thus the second operation turned out to be an overtreatment.
According to previous reports, 25 % of all GISTs develop local recurrence and 33 %
develop distant recurrences; GISTs with more than one mitosis and size larger than
5 cm have an especially poor prognosis [2]. Depending on tumor size and prognostic parameters, an individual follow-up with
endoscopic and radiological examination is recommended. Despite the misjudgement in
our case, this is an interesting diagnostic pitfall which arose from using endoscopic
ultrasonography for the follow-up examination.
