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A unique tumor measuring 8 x 8 x 5 mm and composed of adenoma, adenocarcinoma and mixed carcinoid-adenocarcinoma arising in the ascending colon is reported. The mixed carcinoid-adenocarcinoma, in which adenocarcinomatous and carcinoid components intermingled, originated in the mucosa, penetrated the muscularis mucosa and extended into the submucosa. Immunohistochemically, carcinoid cells were positive for neuroendocrine markers and adenocarcinoma cells were intracytoplasmicly positive for carcinoembryonic antigen. Ultrastructurally, membrane-bound electron dense granules varying in shape, size and electron density were detected in the cytoplasm of carcinoid cells. No mutations of p53 and k-ras genes were detected in adenomatous, adenocarcinomatous or mixed carcinoid-adenocarcinoma components. The morphological appearances of the present case strongly suggests the histogenesis of this tumor in an adenoma-adenocarcinoma-carcinoid tumor sequence.

Immunohistochemical analysis of p53 has become an established method of detecting mutated p53. Immunolocalization of p53 has been extensively studied in tissue sections of many human neoplasms, but not in cytology specimens. Therefore, we performed immunolocalization of p53 in both cytology and tissue preparations obtained from the same specimens in 19 cases of human esophageal squamous-cell carcinoma. Three different antibodies, PAb1801, DO-7, and CM-1, were employed. Positive p53 nuclear immunoreactivity was observed in carcinoma cells, but not in noncarcinomatous cells, in both tissue and cytology preparations. The incidence of p53 positivity was 53% (10/19) in cytology and 42% (8/19) in tissue, and the coincident rate of both results was 89% (17/19). We conclude that immunohistochemistry of p53 in cytology is a useful method for detecting p53 mutations, and may contribute to the diagnosis of malignancy, because it is a simple, easy, and rapid technique.

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