Simultaneous Rectal Schwannoma and Prostatic Adenocarcinoma Detected on FDG PET/CT

Solitary Benign Schwannoma Mimics Residual Malignancy on FDG PET/CT

Schwannomas can be seen in pediatric patients with neurofibromatosis and occur generally in the limbs. Solitary schwannoma rarely occurs in pediatric patients who do not have neurofibromatosis. A 15-year-old girl with Hodgkin lymphoma in the neck underwent follow-up FDG PET/CT scan to monitor the response to the chemotherapy. Although her lesions in the neck were no longer visualized, one focal activity in her left upper back persisted. Excisional biopsy result demonstrated benign schwannoma.

Schwannoma of the colon and rectum: a systematic literature review

Background

Schwannomas of the colon and rectum are rare among gastrointestinal schwannomas. They are usually discovered incidentally as a submucosal mass on routine colonoscopy and diagnosed on pathologic examination of the operative specimen. Little information exists on the diagnosis and management of this rare entity.

The aim of this study is to report a case of cecal schwannoma and the results of a systematic review of colorectal schwannoma in the literature.

Main body

PubMed, Scopus, and Cochrane database searches were performed for case reports and case series of colonic and rectal schwannoma.

Ninety-five patients with colonic or rectal schwannoma from 70 articles were included. Median age was 61.5 years (59% female). Presentation was asymptomatic (28%), rectorrhagia (23.2%), or abdominal pain (15.8%). Schwannoma occurred in the left and sigmoid colon in 36.8%, in the cecum and right colon in 30.5%, and in the rectum in 21.1%. Median tumor size was 3 cm and 56.2% of patients who underwent preoperative colonoscopy had a typical smooth submucosal mass. At pathology, 97.9, 13.7, and 5.3% of schwannomas stained positive for S100, vimentin, and GFAP, respectively. The median mitotic index was 1/50.

Conclusions

Colorectal schwannoma is a very rare subtype of gastrointestinal schwannoma which occurs in the elderly, almost equally in men and women. Schwannoma should be included in the differential diagnosis of a submucosal lesion along with gastrointestinal stromal tumor, neuro-endocrine tumors, and leiomyoma-leiomyosarcoma. Definitive diagnosis is based on immunohistochemistry of the operative specimen. Rarely malignant, surgery is the mainstay of treatment.

Clinical, Morphologic, and Pathologic Features Associated With Increased FDG Uptake in Schwannoma

OBJECTIVE

The objective of this study was to investigate the clinical, morphologic, and pathologic features associated with increased ¹⁸F-FDG uptake in benign schwannomas.

MATERIALS AND METHODS

Twenty-two schwannomas in 22 patients (age range, 25-81 years) who had FDG PET or PET/CT scans and subsequently underwent surgical re-section were retrospectively analyzed. The maximum standardized uptake value (SUV_max) was compared with patient age, sex, tumor location (gastrointestinal vs nongastrointestinal origin), tumor size, gross appearance, intratumoral cellularity, intratumoral infiltration of inflammatory cells, presence of peritumoral lymphoid cuffs, and expression status of glucose transporters 1 and 3 on tumor cells.

RESULTS

The SUV_max of schwannomas ranged from 1.5 to 17.3 (median, 3.7). Significantly higher SUV_max was observed in gastrointestinal schwannomas (n = 4) compared with nongastrointestinal schwannomas (n = 18, p = 0.007) and in schwannomas with peritumoral lymphoid cuffs (n = 5) compared with those without peritumoral lymphoid cuffs (n = 17, p = 0.001). A significant correlation was seen between tumor location and the presence of peritumoral lymphoid cuffs (p < 0.001). Age, sex, tumor size, gross appearance, intratumoral cellularity, intratumoral inflammatory cell infiltration, and expression status of glucose transporters 1 and 3 on tumor cells had no significant correlation with SUV_max.

CONCLUSION

Gastrointestinal schwannomas and schwannomas with peritumoral lymphoid cuffs may be associated with elevated FDG uptake. Knowledge of the features of schwannomas associated with increased uptake may be helpful to avoid misinterpretation of benign schwannomas as malignancy.

Bilateral breast uptake demonstrated on FDG PET/CT scans in 3 male patients with hepatocellular carcinomas

We reported 3 male patients with hepatocellular carcinoma who underwent FDG PET/CT for systemic survey before liver transplantation. All of their scans demonstrated obvious FDG uptake in bilateral breasts. These uptakes might be owing to gynecomastia caused by an increase in free estrogen related to the cirrhotic liver.