PMC8179799_01
Sagittal CT scan representative image demonstrating the tumor's proximity to central arterial vasculature (A). Axial and coronal representative CT images demonstrating tumor proximity to gastric (B and D) and colonic (C) tissues (arrows demarcate points of organ abutment). Representative CT images obtained after 25 Gy of radiotherapy and four cycles of immunotherapy with gold fiducials demarcating the tumor (E-G).
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An abdominal CT revealed a 10.6x8.0x11.7cm mass arising from the pancreatic body, with partial encasement of the splenic artery (Figure 1A). The mass abutted the stomach and splenic flexure of the colon, with evidence of invasion of both organs (Figure 1B-D) without evidence of metastatic disease. Repeat imaging after a total of 4 cycles showed further tumor volume decrease (3.2x2.7x3.1 cm) and cystic degeneration (Figure 1E-G).
Pancreas with treatment effect. H&E stain (A and C) shows areas of necrosis surrounded by lymphocytes consistent with prior tumor bed. CD3 immunohistochemical stain (B and D) highlights CD3+ T lymphocytes surrounding areas of prior tumor bed.
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The pancreatic specimen revealed abundant mucin and necrotic tissue surrounded by a prominent histiocytic and lymphocytic infiltrate with patchy neutrophilic inflammation, indicative of treatment effect, with no residual dysplasia or carcinoma in the pancreas (Figure 2).
(A) H&E stain; 4x; Colon containing residual carcinoma with lymphocytic infiltrate within tumor (black arrowheads) and area of treatment effect (blue arrows). (B) CK7 IHC stain; 40x; CK7 stain highlighting residual carcinoma within colonic mucosa. (C) CD3 IHC stain; 40x; IHC stain highlighting CD3+ lymphocytes within tumor and area of treatment effect. (D) H&E stain; 400x; High power view of residual carcinoma within the colon with numerous tumor infiltrating lymphocytes.
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The resected colon contained a 4 mm segment of poorly differentiated adenocarcinoma within the lamina propria surrounded by a prominent histiocytic and lymphocytic infiltrate (Figure 3).