Poorly differentiated adenocarcinoma misdiagnosed as gastrointestinal stromal tumor: A case report

Table 1 Comparison of pathological findings between endoscopic submucosal dissection biopsy and surgical specimen

Item	ESD biopsy specimen (initial assessment)	Surgical resection specimen (final diagnosis)
Specimen type	Limited endoscopic biopsy (partial submucosal tissue)	Full-thickness gastrectomy specimen
Tumor architecture	Fragmented tissue with spindle cell-like components	Infiltrative growth involving mucosa, submucosa, and muscularis propria
Cellular morphology	Elongated cells with hyperchromatic nuclei; limited structural context	Poorly differentiated adenocarcinoma with marked atypia
Mucosal involvement	Not adequately assessed	Definite ulceration with mucosal invasion
Depth of evaluation	Superficial and limited	Complete assessment of tumor depth
Immunohistochemistry	Not performed at initial stage	Tumor cells positive for epithelial markers (anti-epithelial antigen 1/anti-epithelial antigen 3, CK antibody monoclonal 5.2, CK7, CK8/18, epithelial membrane antigen, partial CEA); CD34 staining limited to vascular endothelial cells; CD117 and discovered on GIST-1 not performed
Diagnostic interpretation	Suggestive of gastrointestinal stromal tumor	Confirmed poorly differentiated adenocarcinoma

ESD: Endoscopic submucosal dissection; CK: Cytokeratin; CEA: Carcinoembryonic antigen; GIST: Gastrointestinal stromal tumor.

Table 2 Previous cases of gastric adenocarcinoma suspected or misdiagnosed as gastrointestinal stromal tumor

Ref.	Age/sex	Endoscopic findings	EUS findings	Diagnostic method	Final diagnosis
Hu et al[24], 2023	64/F	3-cm round SMT-like mass with smooth mucosa	Heterogeneous hypoechoic mass (MP), subtle layer obliteration	ESD	Moderately to poorly differentiated adenocarcinoma
Chen et al[25], 2019	48/F	2-cm SMT near cardia with central ulceration and exposed vessel	Not described	Intraoperative frozen section	Moderately differentiated adenocarcinoma
Liu et al[26], 2025	60/M	2-cm SMT-like mass at the lesser curvature, smooth overlying mucosa	2.0 cm × 0.8 cm well-defined hypoechoic mass (MP)	ESD	Poorly differentiated adenocarcinoma
Lee and Oh[27], 2020	64/F	2-cm lobulated SMT with normal mucosa	19 mm × 11 mm heterogeneous hypoechoic mass (MP), well-circumscribed	Intraoperative frozen biopsy	Signet ring cell adenocarcinoma
Kim et al[28], 2012	57/M	10 cm × 12 cm intraluminal protruding lesion with normal mucosa	Heterogeneous mass (MP) with hyperechoic deposits and necrotic zones	EUS-guided trucut biopsy	Signet ring cell adenocarcinoma
Shin et al[29], 2015	59/F	8-cm protuberant SMT with slight ulceration	Not described	Postoperative pathology	Poorly differentiated tubular adenocarcinoma
Shin et al[29], 2015	68/M	4.8-cm protruding SMT with central ulceration	Not described	Laparoscopic biopsy	Mucinous adenocarcinoma
Li et al[30], 2016	44/M	1-cm sessile polypoid SMT-like lesion with erosion	0.7 cm × 0.8 cm well-defined hypoechoic mass (MP)	ESD with IHC	Poorly differentiated adenocarcinoma

EUS: Endoscopic ultrasound; SMT: Submucosal tumor; MP: Muscularis propria; ESD: Endoscopic submucosal dissection; F: Female; M: Male; IHC: Immunohistochemistry.