Gastrointestinal stromal tumor with secondary thrombocytosis: a case report of a high-risk patient

Abstract

Gastrointestinal stromal tumor (GIST) with secondary thrombocytosis is a rare clinical case, exhibiting specificity in clinical diagnosis and treatment. We report a case of GIST with secondary thrombocythemia to raise clinicians' attention to this disease. On October 11, 2024, a 58-year-old male patient was admitted to the hospital due to "intermittent right lower abdominal pain with increased bowel movements for more than 1 month." The patient had no prior history of tumors, chronic inflammatory diseases, hematologic disorders or family history of genetic disorders. MRI-enhanced scans of the small intestine highly indicated a lymphoma of intestinal origin. Small bowel endoscopy and pathological biopsy revealed mild chronic inflammation of the intestinal mucosa, with intact villous architecture, no plasmacytosis, granulomas, or vasculitis, and no indication of GIST. Laboratory tests showed platelet count of 909 × 10⁹/L, white blood cell count of 11.86 × 10⁹/L, neutrophil ratio of 75.10%, lymphocyte ratio of 15.30% and hemoglobin 101 g/L. Bone marrow biopsy microscopically showed a normal number of megakaryocytes without abnormal aggregation and no myelofibrosis, suggesting there was no obvious hematologic malignancy and the thrombocytosis may have been secondary. The patient underwent partial resection of the small intestine and resection of mesenteric lesions on October 18, 2024. The intraoperative frozen section suggested a stromal tumor. The postoperative pathological biopsy suggested a GIST and genetic testing showed a mutation in the c-KIT gene (Exon 13). Postoperatively, the patient was treated with oral imatinib mesylate (400 mg/d) as adjunctive therapy. Three months after surgery, imaging showed no recurrence, platelet decreased and returned to normal levels.

Keywords: Exon 13; c-KIT; case report; gastrointestinal stromal tumor; secondary thrombocythemia.

Figure 1

Small Bowel Enteroscopy and Histopathological Findings from Endoscopic Biopsy. (A) Enteroscopic examination revealed scattered lymphoid follicular hyperplasia in the terminal ileum. The surrounding mucosa appeared smooth, with well-preserved villous architecture and no evidence of ulceration, mass lesions, or abnormal vascularity. (B) Histological analysis of endoscopic biopsy specimens showed mild chronic inflammatory infiltration in the lamina propria with intact villous architecture. No significant plasma cell infiltration, granuloma, or vasculitis was identified. Lymphoid follicle formation was observed. There was no histological evidence of inflammatory bowel disease, intestinal tuberculosis, or Behçet’s disease.

Figure 2

Magnetic resonance imaging (MRI) features of the abdominal mass. (A) Coronal T2-weighted image showing a well-defined, hyperintense mass in the lower abdomen (left panel, arrow). (B) Axial contrast-enhanced image demonstrating heterogeneous enhancement of the lesion, suggestive of a solid, vascularized tumor (upper right panel, arrow). (C) Axial T1-weighted image revealing a hypointense mass at the corresponding site (lower right panel, arrow).

Figure 3

Bone marrow biopsy showed no evidence of hematologic malignancy. (A) Bone marrow cellularity was within normal limits, and megakaryocytes were adequate in number, exhibiting typical lobulated nuclei without dysplasia (left panel, H&E stain). (B) No abnormal increase or clustering of lymphocytes or plasma cells was observed, and no features suggestive of hematologic neoplasms were identified (right panel, H&E stain).

Figure 4

Histopathological features of the resected tumor showing classic morphology of gastrointestinal stromal tumor (GIST). Spindle-shaped tumor cells were arranged in fascicular and interlacing bundles. The cytoplasm was eosinophilic with indistinct cell borders. The nuclei were elongated or oval, and mitotic figures were readily observed, consistent with a high-risk GIST. (A) Hematoxylin and eosin (H&E), ×4. (B) H&E, ×10. (C) H&E, ×20.

Figure 5

Immunohistochemical staining of the resected tumor specimen confirming the diagnosis of GIST. (A) CD34 staining showed partial positivity in tumor cells. (B) Strong and diffuse membranous positivity for CD117 (c-KIT) was observed. (C) DOG-1 staining was diffusely positive, further supporting the diagnosis of GIST.

Figure 6

Timeline of the clinical course of the patient. The figure illustrates symptom onset, diagnostic workup, surgical treatment, and long-term follow-up. Platelet count values are annotated at key time points.