PMC6292410_01
Imaging for Case 1.. Notes: Pre-treatment (A, B) and post-treatment (C, D) fused axial PET/CT images of the patient's left-sided primary breast lymphoma (A, C) and gastrointestinal stromal tumor of the pancreatic head (B, D). Pre-treatment imaging revealed mildly FDG-avid left breast changes at the site of biopsy-confirmed DLBCL (A), with resolution of these findings after six cycles of R-CHOP chemotherapy (C). Pre-treatment imaging revealed a 5.0 x 6.0 cm duodenal/pancreatic head mass with significant FDG avidity (B); this decreased in size to 4.6 x 5.2 cm after 10 months of imatinib, with continued FDG avidity, suggesting persistent disease despite partial response (D).. Abbreviations: DLBCL, diffuse large B cell lymphoma; FDG, fluorodeoxyglucose; PET, positron emission tomography; R-CHOP, rituximab/cyclophosphamide/doxorubicin/vincristine/prednisolone.
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Subsequent fluorodeoxyglucose positron emission tomography (PET) and CT scans during staging evaluation for her PBL revealed a 5.0 x 6.0 cm mass involving the duodenum and the head of the pancreas (Figure 1). PET/CT performed to pre-operatively assess the duodenal GIST; this PET/CT revealed resolution of the breast mass, with interval decrease in size (4.6 x 5.2 cm) and central cavitation of the duodenal/pancreatic mass suggesting treatment-related necrosis, with continued metabolic activity suggesting persistent disease despite treatment response (Figure 1). Patient, therefore, proceeded to pylorus-preserving pancreaticoduodenectomy, cholecystectomy, and retroperitoneal lymphadenectomy. Pathology revealed a 4.5 cm GIST invading the full thickness of duodenal wall, 1/18 lymph nodes involved by direct tumor extension, negative surgical margins, and less than five mitotic figures per 50 high-power field (HPF; Figure 2).
Case 1 GIST surgical resection pathology findings.. Notes: (A) Gastrointestinal stromal tumor involving the wall of the duodenum (arrowhead). The neoplastic cells showed epithelioid morphology with focal areas of spindle cell morphology. Mitotic figures were few (<5 per 50 high-power fields). (H&E stain; 100x original magnification) (B) DOG1 immunohistochemistry showed diffuse positive staining. (C) Bcl-2 immunohistochemistry showed diffuse positive staining. (Immunohistochemistry with hematoxylin counterstain; 100x original magnification).
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PET/CT performed to pre-operatively assess the duodenal GIST; this PET/CT revealed resolution of the breast mass, with interval decrease in size (4.6 x 5.2 cm) and central cavitation of the duodenal/pancreatic mass suggesting treatment-related necrosis, with continued metabolic activity suggesting persistent disease despite treatment response (Figure 1). Patient, therefore, proceeded to pylorus-preserving pancreaticoduodenectomy, cholecystectomy, and retroperitoneal lymphadenectomy. Pathology revealed a 4.5 cm GIST invading the full thickness of duodenal wall, 1/18 lymph nodes involved by direct tumor extension, negative surgical margins, and less than five mitotic figures per 50 high-power field (HPF; Figure 2). Immunohistochemical staining confirmed positivity of the GIST specimen for DOG1, a highly sensitive and specific marker for GIST, as well as diffuse strong positive staining for Bcl-2 (Figure 2).
PMC6292410_02
Case 2 GIST surgical resection pathology findings.. Notes: (A) GIST comprised of neoplastic cells with spindle cell morphology exhibiting a herringbone growth pattern. Mitotic figures were few (<5 per 50 high-power fields). (H&E stain; 100x original magnification) (B) CD117 immunohistochemistry showed diffuse positive staining. (Immunohistochemistry with hematoxylin counterstain; 100x original magnification).. Abbreviation: GIST, gastrointestinal stromal tumor.
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While the patient was receiving rituximab for her recurrent lymphoma, she underwent abdominopelvic mass excision which revealed a GIST of the small intestinal serosa measuring 21x18 cm with four mitotic figures per 50 HPF, negative margins, and positive tumor staining CD117 and CD34 (Figure 3).