Synchronous Adenocarcinoma of the Appendix Demonstrated on F-18 FDG PET/CT

Synchronous Squamous Cell Carcinoma of Rectum and Anal Canal Detected by FDG PET/CT-A Rare Entity

ABSTRACT

Squamous cell carcinoma is the most common malignancy of the anal canal, and FDG PET/CT is recommended in its nodal staging, radiotherapy planning, and response assessment. We share an interesting case of dual primary malignancy of the anal canal and rectum, which was detected by 18 F-FDG PET/CT and confirmed on histopathology as synchronous squamous cell carcinoma.

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.

A rare case of synchronous appendiceal and cecal cancer

Primary appendiceal cancer is rare, and difficult to diagnose pre-operatively because lack of specific symptoms. This report presents a rare case of synchronous colon and appendiceal cancer. A 50-year-old man was referred to our hospital due to endoscopic submucosal resection (ESD) for early cecal cancer. ESD was performed, and the pathological examination revealed tubular adenocarcinoma with deep submucosal invasion. Laparoscopic ileocecal resection was performed as additional resection after ESD of cecal cancer. There were no obvious abnormalities around the ileocecal region in the preoperative examination. Postoperative pathological examination incidentally revealed a mucosal papillary adenocarcinoma of the appendix, with no residual lesion in the ESD scar. The patient was discharged on the seventh postoperative day. Synchronous appendiceal and colon cancer is extremely rare in past reports. Here, we report the case details and review previous case reports.

Normal patterns of 18F-FDG appendiceal uptake in children

BACKGROUND

Prior to interpreting PET/CT, it is crucial to understand the normal biodistribution of fluorodeoxyglucose (FDG). It is also important to realize that the normal biodistribution can vary between adults and children. Although many studies have defined normal patterns of pediatric FDG uptake in structures like the thymus, brown fat and bone marrow, patterns of normal pediatric bowel activity, specifically uptake within the appendix, have not been well described. Active lymphoid tissue has increased FDG uptake when compared with inactive tissue. Since children have more active lymphoid tissue than adults, and because the appendix contains aggregated lymphoid tissue, we postulated that appendiceal uptake may be increased in pediatric patients.

OBJECTIVE

To define the normal level of appendiceal FDG activity in children by evaluating a series of consecutive FDG PET/CT scans performed for other indications.

MATERIALS AND METHODS

After obtaining IRB approval, we retrospectively reviewed 128 consecutive whole-body pediatric FDG PET/CT examinations obtained for a variety of clinical indications. CT scans on which the appendix could not be visualized were excluded from analysis. CT scans on which the appendix could be visualized were evaluated for underlying appendiceal pathology. Studies with appendiceal or periappendiceal pathology by CT criteria were excluded. A region of interest (ROI) was placed over a portion of each appendix and appendiceal maximum standardized uptake value (SUVmax) was calculated. If an adjacent loop of bowel activity interfered with accurate measurements of the appendix SUVmax, the scan was excluded from the analysis. A chart review was performed on patients with elevated appendiceal SUVmax values to ensure that the patients did not have clinical symptomatology suggestive of acute appendicitis. When the appendix or a portion of the appendix could be visualized and accurately measured, the SUVmax was determined. SUVmax of the appendix was compared to the SUVmax of normal liver and ratios were recorded.

RESULTS

A total of 128 scans were reviewed, patient ages 1 month to 21 years (mean age: 11.6 years). Thirty-one scans were excluded because of inability to visualize the appendix on CT. No scans were excluded for appendiceal/periappendiceal pathology on CT or chart review. No scans had to be excluded for inability to obtain an accurate SUVmax measurement because measurements were calculated on portions of the appendix separate from adjacent bowel using small ROIs. Maximum appendiceal SUVs ranged from 0.5 to 9.4 (mean: 2.2) with an appendix-to-liver background ratio ranging from 0.3 to 3.1 (mean: 1.1).

CONCLUSION

FDG uptake in the appendix is typically similar to that of background activity. However, slight variations in appendiceal FDG uptake do occur, which should not be misinterpreted as pathological.

Incidentally Discovered Adenocarcinoma in situ of the Appendix in a Young Woman

Primary appendiceal adenocarcinoma is an infrequent disease. This report presents a rare case of incidentally discovered carcinoma in situ of the appendix. A 35-year-old parturient female simultaneously underwent appendectomy and oophorectomy due to an ovarian abscess that adhered to the appendix during cesarean section. Although her excised appendix showed no apparent tumorous lesion, histopathological examination revealed carcinoma in situ in the excised appendix. She underwent additional right hemicolectomy a few days later due to the possibility of a positive surgical margin. Histopathological examination detected no malignant cells in the resected specimen. She was discharged without any complications and has since remained healthy. Appendiceal adenocarcinoma is generally considered to be difficult to diagnose during the early stage because it seldom shows any specific findings. This results in a poor prognosis. Histopathological examination is not always conducted for appendices resected during other surgery. However, the current study suggests that a careful routine histopathological examination of excised appendix, as well as careful preoperative examination and detailed intraperitoneal inspection during surgery, is indeed important to detect occult appendiceal tumors.

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.