Primary Duodenal Squamous Cell Carcinoma on 18F-Flurodeoxyglucose Positron Emission Tomography/Computed Tomography

A 48-year-old woman complained with repeated vomiting and pallor over 3 months. Laboratory results revealed a decrease in hemoglobin (80 g/L, reference range > 110 g/L), and no other findings (including tumor markers) were abnormal. Next, abdomen computed tomography (CT) revealed a duodenal mass, which may be malignant. To further define the nature and stage of the lesion, the patient underwent ¹⁸F-flurodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) scan. The maximum intensity projection (MIP) image (Figure 1a) demonstrated a high radioactivity (arrow) in the middle abdomen. The axial (Figure 1b), coronal (Figure 1c), and sagittal (Figure 1d) images of the abdomen displayed a solid lesion (arrow) with the size of 61 mm × 34 mm and a SUV_max of 15.6 in the horizontal part of the duodenum. In addition, peripheral lymph nodes with the maximum size of 8 mm × 5 mm showing mild FDG activity (SUV_max: 2.0) were noted (images not shown). The patient received surgical resection of the duodenal lesion (Figure 2a) and peripheral lymph nodes. Pathological examination (Figure 2b, hematoxylin–eosin staining and original magnification: ×100) from the duodenal specimen showed tumor cells arranged in nests with formation of keratin pearls. Immunohistochemistry indicated positive staining for P40 (Figure 2c, original magnification: ×100). These findings were consistent with a diagnosis of duodenal squamous cell carcinoma (SCC). Besides, peripheral lymph node metastases were also confirmed.

SCC of the duodenum is extremely rare and is more likely to represent metastasis from primary SCC originating in other sites, such as the head and neck, lungs, or cervix. Only occasional cases of primary SCC of the duodenum have been reported in the literature. There are four possible pathogenesis of primary duodenal SCC: (1) malignant transformation of heterotopic squamous epithelium; (2) pluripotential stem cells differentiate to malignant squamous cells; (3) squamous metaplasia malignant change due to chronic mucosal damage; and (4) adenocarcinoma transformed into adenosquamous carcinoma and eventually to SCC. Surgery might be the cornerstone in the management of such kind disease. Given the value of the differentiation of metastatic or primary duodenal SCC for treatment options and prognosis, establishing a correct diagnosis is essential. Traditionally, CT scanning has been the major imaging modality for diagnosing abdominal malignancies, which is not particularly sensitive for detecting duodenal malignancies. Increased FDG uptake in the duodenum is not uncommon, but it is usually physiological or inflammation-related. However, our case suggests that duodenal malignancy should be considered in the differential diagnosis when focal abnormal FDG uptake is present in the duodenum, especially when accompanied by a corresponding mass-like lesion on CT imaging. Furthermore, in this case, whole body ¹⁸F-FDG PET/CT was helpful in distinguishing primary duodenal tumor from metastasis as well as identifying metastatic lesions and aiding in the clinical staging. Besides, primary duodenal SCC should be differentiated from duodenal adenocarcinoma, lymphoma, neuroendocrine carcinoma, and gastrointestinal stromal tumor.

Yinting Hu: writing – original draft (lead). Lei Jiang: writing – review and editing (lead).

This study was approved by the Ethics Committee of Guangdong Provincial People's Hospital (Approval Number: KY2023-020-01).

Informed consent was waived due to the retrospective nature of this report.

The authors declare no conflicts of interest.