case_images: PMC11372762_01
case_images: The morphology and immunoprofile of the original colonic biopsy. (a) There is proliferation of sheets of cells with signet-ring like appearance that contain intracytoplasmic mucin, highlighted by Diastase PAS (Inset). (b) CDX-2 immunostain is positive in the tumor cell nuclei. (c) Synaptophysin is positive in the tumor cell cytoplasm. (d) INSM-1 is positive in tumor cell nuclei. (e) and (f) Loss of PMS2 and MLH1 nuclear staining in the tumor cells, in the presence of internal positive control, consistent with MMR-deficient tumor. (g) BRAF p. V600 E shows strong diffuse cytoplasmic staining.
case_images: 10.1177_20363613241266036-fig1.jpg
case_images: PMC11372762_01_10.1177_20363613241266036-fig1.jpg
case_images: fig1-20363613241266036
case_images: While the second component is composed of monomorphic smaller cells with indistinct cytoplasm and high nuclear-to-cytoplasmic ratio with nuclei showing homogenous fine chromatin with no evidence of prominent nucleoli (Figure 1(a)). INSM-1 (Figure 1(d)), and SATB2 (not shown), but were immunonegative for Chromogranin-A and CD56. In addition, MMR proteins (MLH1 and PMS2) showed loss of nuclear staining (Figure 1(e) and (f)) while MSH-2 and MSH-6 nuclear staining was intact. V600 E (Figure 1(g)) which was positive, in support of MLH-1 methylation.