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(A) Subcutaneous nodules in the left anterior abdominal wall (arrow); (B) Surgical specimens after resection of subcutaneous nodule; (C) Abdominal computed tomography showed a subcutaneous nodule in the left anterior wall (arrow); (D) Histology of the subcutaneous nodule showed that the tumor cells were spindled (H&E staining, x400); (E-G) CD117, DOG1 and CD34 immunohistochemistry is positive in the subcutaneous metastasis, respectively.
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Due to suspected subcutaneous metastasis, excision biopsy was performed, and pathological examination revealed a tumor with spindled morphology, which stained positive for CD117, DOG1 and CD34 (Figure 1).
Sequencing results of KIT exon 11 and 13. The obvious double peaks in the sequencing diagram demonstrates there is mutation (red arrow). (A) and (B) Forward and reverse sequencing of KIT exon 11 (c.1740_1741ins(p.P577-H580dup)); (C) and (D) Forward and reverse sequencing of KIT exon 13 (c.1924A>G(p.K642E)).
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Additional molecular analysis confirmed mutations in KIT exon 11 and 13 (Figure 2).
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Immunohistochemical staining of SM-GIST (Case 3) showed the following: (A) CD117 (positive, x100); (B) CD34 (positive, x100); (C) DOG1 (positive, x100); (D) SDHB (negative, x100).
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The subsequent histopathological analysis revealed a tumor with epithelioid morphology, which stained positive for DOG1, CD117 and CD34 but negative for succinate dehydrogenase B (SDHB) (Figure 3).
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Immunohistochemical staining of a primary tumor and skin metastasis. Primary tumor: (A) H&E staining, x100; Immunohistochemical staining showed the following: (B) CD117 (negative, x100); (C) DOG1 (positive, x100); (D) CD34 (positive,x100). Skin metastasis: (E) H&E staining, x100; Immunohistochemical staining showed the following: (F) CD117 (negative, x200); (G) DOG1 (negative,x200); (H) CD34 (positive,x200).
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The histological features were compatible with the known primary tumor, but the tumor only stained positive for CD34 and molecular analysis showed no mutation in KIT/PDGFRA (Figure 4).