Supplementary Material for: Intestinal Subocclusion: An Unexpected Diagnosis in a Common Clinical Presentation

Gastrointestinal (GI) metastases from lung cancer are frequently identified in autopsy series (up to 14%), yet they are rarely recognized in clinical practice, with a reported incidence of 0.2%–1.8% [1]. Most patients are asymptomatic, but some may present with iron-deficiency anemia, abdominal pain, bleeding, obstruction, or perforation—often mimicking primary GI diseases [2,3]. This case report describes an unusual initial presentation of metastatic disease with GI involvement, manifesting as iron-deficiency anemia and acute gastrointestinal symptoms due to jejunal infiltration.
We report the case of an 81-year-old male presented to the Emergency Department with a three-week history of asthenia. His past medical history included diabetes, high blood pressure and dislipidemia. Blood tests revealed iron-deficiency anemia, leading to outpatient endoscopic evaluation. Colonoscopy identified an 8 mm polyp in the descending colon, submitted for histopathological analysis.
Three weeks later, he returned with abdominal pain, vomiting and diarrhea. Laboratory tests showed leukocytosis and elevated CRP. A CT enterography (Fig 1) revealed jejunal loop distension proximal to a segment of concentric wall thickening, along with a nodular lesion in the left lung. Conservative management led to temporary clinical improvement.
Histology of the colonic polyp revealed a malignant epithelial neoplasm with basaloid phenotype, squamous features, vascular invasion and focal necrosis. Dermatological evaluation excluded cutaneous malignancy. A PET-CT revealed hypermetabolic activity in jejunal/ileal loops, bone (femur and scapula) and lungs. Enteroscopy revealed an ulcerated jejunal lesion (Fig 2); biopsy confirmed squamous cell carcinoma (Fig 3). Pulmonary nodule biopsy revealed similar histology. Brain magnetic resonance imaging (MRI) revealed three cortical/subcortical micrometastases involving the temporal, parietal, and occipital lobes. A diagnosis of diffuse metastatic squamous cell carcinoma of likely pulmonary origin (T1b, N2, M1b: Stage IVb) was made. The patient was started on immunotherapy with pembrolizumab, After the 16th cycle, oligoprogression of the disease was identified, characterized by an increase in the size of a pulmonary nodule. The patient underwent targeted radiotherapy without complications, achieving a partial response. Pembrolizumab was subsequently resumed (currently on the 25th cycle), and the patient remains clinically stable, with no new subocclusive episodes reported during one year of follow-up.

Secondary involvement of the GI tract by non-GI primary malignancies is uncommon and frequently clinically silent, making diagnosis particularly challenging [4]. Small bowel metastases account for about 10% of all neoplasms at this site [5]. The majority of these lesions arise from adenocarcinomas, whereas squamous cell carcinoma (SCC) accounts for a smaller proportion of metastatic tumors involving the small intestine [1]. In lung cancer, all histological subtypes may metastasize to the small bowel, with SCC responsible for approximately 28.1% of cases [3]. Predominantly affecting elderly male smokers, SCC of the lung typically presents at an advanced stage, often with distant metastases and poor prognosis [1]. Although GI involvement is rare, early recognition is crucial, as it may enable timely initiation of systemic therapy, as illustrated in the present case with the introduction of pembrolizumab. This case highlights the need to consider metastatic disease in the differential diagnosis of elderly patients with unexplained anemia and acute GI symptoms. Prompt use of endoscopy and imaging, guided by clinical suspicion, is vital to establish an accurate diagnosis and enable timely management.