Appendiceal schwannoma detected by FDG-PET/CT

Appendiceal schwannoma - report of a case and literature review

Appendiceal tumours encompass a wide spectrum of differential diagnoses and frequently present with clinical features of appendicitis. We report the case of a 43-year-old woman who presented with epigastric pain, dyspepsia and bloating. An atypical right para-iliac mass was detected on abdominal ultrasound, and computed tomography (CT) identified an appendiceal tumour. The tumour subtype remained indeterminate following Gallium-68 Dotatate positron emission tomography (PET); however, an appendiceal neuroendocrine tumour was suspected. Surgical resection with laparoscopic en bloc appendicectomy and limited caecectomy was performed, and histopathological assessment confirmed an appendiceal schwannoma. The report is followed by a review of the literature. To our knowledge, there have been fourteen reported cases of appendiceal schwannoma. The preoperative diagnosis can be challenging and appendiceal schwannoma had not been suspected in any of the reported cases, while a suspected diagnosis of neuroendocrine tumour or gastrointestinal stromal tumour was common. Definitive diagnosis requires immunohistochemical assessment and S100 is the hallmark. No personal or family history of underlying neurofibromatosis (NF) type 1 or type 2 has been reported to date. As for other gastrointestinal schwannomas, complete surgical resection is the recommended treatment for appendiceal schwannoma. Following this, despite lack of long-term follow-up, no cases of recurrence have been reported thus far.

Appendiceal schwannoma presenting as acute appendicitis

Schwannomas are nerve sheath tumors that rarely occur in the gastrointestinal tract. In the gastrointestinal tract, schwannomas are mostly found in the stomach and small bowel. Herein, we describe a case of appendiceal schwannoma that caused appendix obstruction and developed acute appendicitis. An 83-year-old woman was admitted to the emergency department with 3 days' history of abdominal pain. She had tenderness and rebound tenderness in the lower right quadrant. Computed tomography revealed a 1.3 cm mass in the appendix orifice, with associated distal appendiceal dilatation and wall thickening. The patient underwent emergency surgery (laparoscopic partial cecectomy). Histopathological examination confirmed that the mass was a schwannoma and was associated with acute suppurative appendicitis. Our case is significant in that it adds to another rarely reported case of appendiceal schwannoma. Moreover, it is important to recognize the presence of an appendiceal tumor associated with acute appendicitis.

Appendiceal Neuroendocrine Tumor Detected by 18F-FDG PET/CT

ABSTRACT

Appendiceal neuroendocrine tumor is very rare, and it is difficult to make a definite diagnosis before operation due to absence of specific clinical features. We report the 18F-FDG PET/CT findings in a patient with an appendiceal neuroendocrine tumor.

Pancreatic Schwannoma on FDG PET/CT

A 55-year-old woman underwent FDG PET/CT to evaluate a pancreatic mass. The images showed elevated FDG activity in the uncinated process of the pancreas, suggestive of malignancy. However, pathological examination from the resected lesion demonstrated pancreatic schwannoma.

Laparoscopic Resection of Appendiceal Schwannoma

Background

Schwannoma arises from Schwann's cell of the neural sheath. Schwannoma of the large intestine, particularly of the appendix, is rare. We report a case of appendiceal schwannoma resected using laparoscopic surgery.

Case Presentation

A 75-year-old man was referred to our hospital for abdominal fullness and nausea since 2 months. Abdominal CT revealed a well-demarcated oval mass of 25 mm at the tip of the appendix. Contrast-enhanced CT revealed a lesion with gradually enhanced contrast from the arterial phase to the equilibrium phase. Abdominal US revealed a well-demarcated hypoechoic tumor. Preoperative diagnosis indicated appendiceal mesenchymal or neuroendocrine tumor. Ileocecal resection with D3 lymph node dissection was performed. Pathological and immunohistochemical findings confirmed the diagnosis of appendiceal schwannoma.

Conclusions

For determining the surgical procedure of nonepithelial tumor of the appendix, preoperative diagnosis of mesenchymal or neuroendocrine tumors is required. However, appendiceal schwannoma is extremely rare, and its characteristic findings have not yet been established. Accumulating cases of appendiceal schwannomas is necessary for improving imaging diagnosis and surgical treatment.

Gastric schwannomas revisited: has precise preoperative diagnosis become feasible?

BACKGROUND

Gastric schwannomas are not common but are clinically important in terms of differential diagnosis from other submucosal lesions. The precise preoperative diagnosis, however, has been challenging mainly owing to the lack of specific findings in conventional imaging studies. The aim of this study was to revisit the possibilities and limitations of modern preoperative diagnostic modalities for gastric schwannomas.

METHODS

Fourteen consecutive patients with a final pathological diagnosis of gastric schwannoma were retrospectively analyzed. Data included demographics, preoperative imaging studies/diagnosis, surgery, histopathology, and follow-up results.

RESULTS

The series included 6 males and 8 females, with a median age of 49 years (range 26-68 years). No symptoms were presented, except for 1 patient with epigastric pain. The tumors were located in the upper (n = 5), middle (3), and lower stomach (6), with a median size of 41 mm (range 20-75 mm). Twelve schwannomas (86%) showed homogeneous enhancement on computed tomography. Ulceration was seen on endoscopy in 4 of 12 available cases (33%). Positron emission tomography was performed in the last 4 patients, showing fluorodeoxy-glucose uptake in all cases (100%). A preoperative diagnosis of schwannoma was not obtained in the majority of cases (13/14, 93%); only 1 case was correctly diagnosed, by endoscopic aspiration cytology. Laparoscopic partial gastrectomy was attempted and completed in 13 cases. The patients have been followed up for 4.7 years (range 2.1-20.3 years), with no recurrencesor metastases and acceptable gastrointestinal function.

CONCLUSIONS

The precise preoperative diagnosis of gastric schwannomas remains difficult even with modern imaging studies. Surgery, therefore, should be positively considered for patients without a conclusive preoperative diagnosis.

PET/CT appearance of appendiceal adenocarcinoma

Appendiceal cancer is rare and is associated with a poor prognosis because it is usually found at an advanced stage. We report the case of a 58-year-old man with appendiceal adenocarcinoma, who complained of right lower abdominal malaise for a couple of months. The tumor was detected early on contrast-enhanced computed tomography and F-18 FDG PET/CT. It appeared as an obvious enhancement and intense abnormal tracer uptake focus in front of the right psoas major, which was easily misinterpreted as an enlarged lymph node.

Gastric schwannomas show an obviously increased fluorodeoxyglucose uptake in positron emission tomography: report of two cases

Schwannomas are tumors originating from any nerve that has a Schwann cell sheath. Gastrointestinal (GI) schwannomas represent only 3% of all GI mesenchymal tumors. The stomach is the most common site of GI schwannomas, and schwannomas account for 0.2% of all gastric neoplasms. This report presents two cases of gastric schwannomas showing increased [18F]fluorodeoxyglucose (FDG) uptake on positron emission tomography (PET; maximum standardized uptake value 7.10 and 6.05). Additional immunohistochemical staining of glucose transporter type 1 (GLUT1) and the autocrine motility factor (AMF) was conducted after the tumors were resected, to identify the mechanism that increased FDG uptake on PET. Immunohistochemical expression of AMF was positive in both cases, whereas GLUT1 was negative. Autocrine motility factor is also known as phosphoglucose isomerase. However, the mechanism by which FDG is accumulated in schwannoma cells is uncertain, and may be related to intracellular glycolytic activity.