Gastrointestinal mesenchymal tumors are classified into three types by immunohistochemical staining, namely gastrointestinal stromal tumor (GIST), leiomyoma, and schwannoma. Schwannoma arises from the Schwann’s cell, which covers the peripheral nerves [
A 75-year-old man was referred to our hospital for abdominal fullness and nausea since 2 months. He had a medical history of hypertension and hyperlipidemia and a surgical history of the right inguinal hernia. The patient’s laboratory findings were within normal limits. Abdominal computed tomography (CT) revealed a well-demarcated oval isodensity mass of 25 mm at the tip of his appendix. Contrast-enhanced CT revealed a lesion with gradual homogeneous contrast enhancement from the arterial phase to the equilibrium phase (Figure
Abdominal CT showed well-defined isodensity oval mass at the tip of appendix (a). In contrast-enhanced CT, the lesion was gradually enhanced homogeneously from arterial phase (b) to equilibrium phase (c).
Abdominal ultrasonography showed that a well-demarcated hypoechoic mass
Preoperative diagnosis indicated appendiceal neuroendocrine tumor (NET) G1 or gastrointestinal mesenchymal tumors, such as GIST. Malignancy could not be ruled out; therefore, laparoscopic ileocecal resection with D3 lymph node dissection was recommended. Intraoperative findings revealed a well-demarcated tumor at the tip of the appendix, with no invasion into the surrounding tissue. This observation was similar to the preoperative imaging findings. According to another intraoperative finding, dissecting the adhesion between the terminal ileum and the peritoneum, which was the effect of the past herniorrhaphy, was necessary. The operation time was 167 min, and the amount of blood loss was 100 ml.
Pathological findings revealed a well-demarcated tumor originating from the muscular layer at the tip of the appendix and spindle-shaped heterotypic cells proliferating in a bundle. Vascular invasion and lymph duct invasion were not detected. No tumor cells were found in the dissected lymph node. Immunohistochemical studies revealed negative values for KIT and CD34 and positive values for S-100 protein (Figure
Pathological finding in HE staining showed spindle-shaped heterotypic cells proliferating in a bundle (a). In immunohistochemical studies, the nucleus stained by S-100 protein (b).
Verocay [
Schwannoma can occur at any location throughout the body along the peripheral nerves [
Gastrointestinal schwannoma assumes the form of a submucosal tumor. The incidence of schwannoma has been reported to be 2%–6% of all submucosal tumors of the intestine [
Regarding appendiceal NET G1, some cases of appendicular goblet cell carcinoid, which exhibit pathological characteristics of both carcinoid and adenocarcinoma, have been recently reported. Goblet cell carcinoma of the appendix requires a treatment approach similar to that required for a colorectal malignant tumor. Some reports of additional resection surgery for lymph node dissection after appendectomy for appendiceal goblet cell carcinoma are available [
Gastrointestinal schwannoma and GIST show similar imaging findings [
Characteristic CT findings of mesenchymal tumor and NET G1.
Density | Shape | Margins | Enhancement pattern | Enhancement phase | |
---|---|---|---|---|---|
Schwannoma | Isodensity | Round or oval | Well-defined | Homogeneous | Delayed phase |
GIST | Isodensity | Round or oval irregular | Well-defined | Homo or heterogeneous | Nonspecific |
Leiomyoma | Isodensity | Round or oval | Well-defined | Homogeneous | Nonspecific |
NET G1 | Bowel wall: isodensity | Appendix: diffuse mural thickening | Well-defined | Homogeneous | Arterial phase |
Characteristic US or EUS findings of mesenchymal tumor and NET G1.
Layer origin | Margins | Feature with US | ||
---|---|---|---|---|
Schwannoma | 4th layer | Well-defined | Hypoechoic | Homogeneous |
GIST | 4th layer | Well-defined | Hypoechoic | Homo-heterogeneous |
Leiomyoma | 4th layer | Well-defined | Hypoechoic | Homogeneous |
NET G1 | 2nd~3rd layer | Well-defined | Hypoechoic | Homogeneous |
[18F]Fluorodeoxyglucose (FDG) positron emission tomography (PET) has been used for detecting malignant tumor. However, there are several reports of gastrointestinal schwannoma with increased FDG uptake, among which is a case of appendiceal schwannoma detected by FDG-PET reported by Nishio et al. [
In our case, abdominal CT revealed a well-defined oval mass of 25 mm at the tip of the appendix. Contrast-enhanced CT revealed the mass with gradual homogeneous contrast enhancement from the arterial phase to the equilibrium phase. Several 5 mm lymph nodes surrounding the ileocolic artery were identified. Abdominal US revealed a well-demarcated hypoechoic hypervascular mass and some cystic area. The CT findings were similar to the known findings of schwannoma. In the US findings, the partial cyst region was different from that reported in the general findings of schwannoma, suggesting the possibility of it depicting the Antoni B area. In the abdominal US, the wall structure was not maintained, and the evaluation of the localized layer of the wall was difficult. Abdominal US may be useful for the diagnosis rather than EUS if the digestive tract wall structure of the appendix can be depicted. According to Bucher et al. [
The standard treatment for schwannoma is complete resection, and several cases of laparoscopic surgery for schwannoma of the large intestine have been reported [
In this case, our preoperative diagnosis was appendiceal NET or mesenchymal tumor with a >2 cm mass. According to the JSCO guideline, ileocecal resection or right hemicolectomy with lymph node dissection was recommended. The presence of enlarged lymph nodes also contributed to this recommendation of lymph node dissection. Currently, regarding the diagnosis of the nonepithelial tumor of the appendix, such as mesenchymal tumor and NET, it is necessary to decide a surgical treatment according to both gastrointestinal mesenchymal tumor and NET guidelines.
We describe a case of appendiceal schwannoma resected using laparoscopic surgery. There are few reports of gastrointestinal mesenchymal tumors, including appendiceal schwannoma; therefore, characteristic clinical findings of appendiceal schwannoma remain unclear. Thus, accumulating cases of appendiceal schwannoma are warranted for improving the imaging diagnosis and surgical treatment of appendiceal schwannoma.
This report was performed in accordance with the ethical standards noted in the appropriate version of the Declaration of Helsinki.
Written informed consent was obtained from the patient for publication of this report.
The authors have no conflicts of interest to declare.
The authors would like to thank Enago (