Sustained Clinical Complete Response after Discontinuation of Trastuzumab-deruxetecan Due to Interstitial Pneumonia for HER2-positive Gastric adenocarcinoma with Enteroblastic Differentiation (GAED): A Case Report.

Trastuzumab deruxtecan (T-DXd) has demonstrated remarkable efficacy as a third- or later-line chemotherapy for human epidermal growth factor receptor 2 (HER2)-positive advanced gastric and gastroesophageal junction adenocarcinomas. However, it may cause pneumonitis, and its efficacy in rare histologies such as gastric adenocarcinoma with enteroblastic differentiation (GAED) remains unclear. A 74-year-old woman with unresectable HER2-positive GAED and lung metastasis received T-DXd as a fifth-line chemotherapy. Treatment was discontinued after 15 cycles owing to drug-induced pneumonitis; however, the patient achieved a sustained complete response for 14 months without subsequent chemotherapy or the exacerbation of pneumonitis. T-DXd was effective in HER2-positive GAED.

Hyperplastic polyp-like adenoma: a subtype of colonic adenoma with a proliferative zone confined to the lower two-thirds of the crypt.

BACKGROUND: The proliferative zone of colonic adenomas is confined to the upper third of the crypt or is scattered along its entire axis. In contrast, there are unusual adenomas with proliferative zones confined to the lower two-thirds of the crypt. We investigated the frequency and endoscopic features of adenomas with lower proliferative zones. METHODS: We retrospectively reviewed consecutive patients who underwent colonoscopies between September 2022 and March 2023 at the Toyoshima Endoscopy Clinic. Colorectal polyps were endoscopically assessed using the Japan Narrow-Band Imaging Expert Team (JNET) classification. All resected polyps were histologically examined, and the proliferative zone locations were assessed in the adenomas. RESULTS: The frequency of adenomas with a lower proliferative zone was 1.8% (44/2420) in adenomas. Among these adenomas, JNET type 1 incidence was 43.2% (19/44), which was significantly higher than that in adenomas with a normal proliferative zone. Adenomas with a lower proliferative zone were diminutive (mean size: 2.5 mm) and prone to develop in the proximal colon. CONCLUSION: Colonic adenomas with proliferative zones confined to the lower two-thirds of the crypt often appear as diminutive, hyperplastic polyps.