Gastric cancer causing Schnitzler's metastasis: case report and systematic review of the features.

Background: Rectal metastasis from gastric cancer (GC), also known as Schnitzler's metastasis, is a rare phenomenon. The clinicopathological characteristics, outcomes, and prognostic factors of this condition remain poorly understood.

Methods: We describe a case of GC causing Schnitzler's metastasis and present a systematic review on case reports and case series. Data extracted and analyzed include clinicopathological features, treatment modalities received, outcomes, and follow-up.

Results: A total of 34 records, including our own, encompassing 41 cases were incorporated into the study. The median age of patients at admission was 59 years, with females accounting for 53.7% of cases. The predominant histological subtype of Schnitzler's metastasis was moderate-to-poorly differentiated adenocarcinoma, representing 31 cases (86.1%). Among the patients in this cohort, 38.9% exhibited signet-ring cell carcinoma. Regarding the initial diagnosis of GC, 28.6% were categorized as stage IIIA, and 28.6% were classified as stage IV. The median overall survival (OS) time was 72 months (95% confidence interval [CI]: 27-NA), while the median OS since the diagnosis of metastatic cancer was 16 months (95% CI: 9-NA).

Interpretation: Schnitzler's metastasis presents a challenge in the pathology of colorectal endoscopy and may lead to treatment delays. Imaging features such as increased thickness of the intestinal wall and significant layered enhancement can aid in diagnosis; however, deep core biopsy of intestinal lesions remains the gold standard for diagnosing rectal metastases. Accurately distinguishing rectal metastases from primary rectal cancer is crucial for preventing unnecessary therapeutic interventions.