Case Report: Tumor-related hemorrhage determined treatment sequencing in blastic plasmacytoid dendritic cell neoplasm coexisting with gastric cardia adenocarcinoma.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and highly aggressive hematologic malignancy that commonly presents with skin involvement and may also involve the bone marrow, peripheral blood, and lymph nodes. The coexistence of BPDCN with a primary solid tumor is extremely uncommon and poses substantial diagnostic and therapeutic challenges. We report a 70-year-old man who was first diagnosed with BPDCN after excision of a left forearm lesion and later developed recurrent hematemesis during chemotherapy. Subsequent endoscopic evaluation revealed a bleeding cardia lesion, and repeat biopsy confirmed poorly differentiated gastric cardia adenocarcinoma. After multidisciplinary evaluation, radical gastrectomy was performed first to control tumor-related bleeding, after which systemic chemotherapy for BPDCN was resumed. This case suggests that, in BPDCN patients who develop hematemesis, progressive anemia, or weight loss during treatment, prompt evaluation for a second primary gastrointestinal malignancy is warranted, and control of active tumor-related bleeding may need to precede hematologic therapy.