Histological examination confirmed surface ulceration with destruction and replacement of the underlying submucosa and muscle wall by an undifferentiated tumour arranged in sheets. These are confirmed on immunohistochemistry to be lymphoid (B-cell) in nature.
Low power of bowel wall with replacement by sheets of tumour cells.
High power of tumour cells showing large irregular nuclei, large nucleoli, and minimal cytoplasm. The cells show no evidence of differentiation, including no glandular differentiation (carcinoma) or melanin pigmentation (melanoma).
CD20 stain (B-cell marker) - There is positive staining indicating a B-cell lineage. The T-cell stains showed reactive background T-cells only.
Cytokeratin (epithelial marker) - negative.
S-100 (melanoma marker) - negative.