A 56-year-old male visited our outpatient clinic for the examination for rectal polyp pointed out by barium enema. A granular superficial spreading tumor of the cecum was disclosed by colonoscopy. Biopsied specimen from the tumor showed a carcinoma in tubulovillous adenoma. The tumor resected revealed carcinoma in tubulovillous adenoma with severe atypia.
Histologically the carcinoma and tubulovillous adenoma with severe atypia are indistinguishable on HE stain. Therefore, we stained the tumor immunohistochemically, with Ki-67 and p53 antibodies, to differentiate objectively carcinoma from adenoma with severe atypia. Many Ki-67 positive cells in both tissues reveal high grade proliferation. This suggests whole tissue is carcinoma. On the other hand, neither was stained by p53 although the immunohistochemistry with the gene is useful for the detection of cancer. Thus we could not objectively decide whether the whole is cancer or the cancer exists in part. Tumors stained by p53 have a tendency to invade more deeply.
Generally speaking, a granular superficial spreading tumor has a tendency to grow rather horizontally than vertically in the colon mucosa. The immunohistochemistry in this case as mentioned above supports this.
