Histopathologic reassessment of so-called colonic adenoma

 
We studied 30 cases of previously diagnosed "colonic adenomas." These were colonoscopic polypectomy or surgical colectomy specimens that were submitted for routine histopathologic analysis. The specimens were fixed with 10% formalin and processed for histopathology. Tissue sections stained with hematoxylin and eosin were examined with conventional light microscopy. In all of the cases of so-called colonic adenomas we studied, it was obvious that the neoplastic cells were all confined in the colonic epithelium. In addition, they showed most or all of the following histopathologic features (Figs. 2–5).
 
  1. Increase in length of the crypts and crowding of them at scanning magnification.
  2. Irregularity in shape of the crypts.
  3. Decrease or loss of differentiation or maturation as evident by a decrease in the number of goblet cells and in the size of mucin vacuoles.
  4. Crowding of nuclei seen as stratification.
  5. Decrease in amount of cytoplasm, enlargement of nuclei, and increase of nuclear to cytoplasmic ratio.
  6. Nuclear hyper- and heterochromasia.
  7. Increase in number of mitotic figures, present at all levels of the crypts including the surface.
  8. Single cell necrosis.

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View Figure  		Fig. 2  A so-called colonic adenoma with its stalk. A: In comparison with the stalk, which is lined by normal colonic mucosa, the so-called adenoma shows obvious loss of maturation and crowding of hyperchromatic nuclei. B: The stalk lined by normal mucosa. C: The so-called adenoma. Note the nuclear hyperchromasia, enlargement of nuclei, increase of nucleus to cytoplasm ratio, nuclear crowding and loss of maturation (decrease in the number of goblet cells as well as in the size of mucin vacuoles).

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View Figure  		Fig. 3  A tiny (2 mm in size) example of so-called colonic adenoma. A: Even at scanning magnification, nuclear hyperchromasia and loss of maturation are evident. B, C: There is crowding of hyperchromatic, elongated nuclei, with increased number of mitotic figures. The numbers of goblet cells are diminished even on the surface of the lesion (loss of maturation).

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View Figure  		Fig. 4  A so-called colonic adenoma of 2 cm in size. A: A pedunculated polypoid lesion. B: Irregularity in shape of the crypts. C–D: There is stratification with a markedly diminished number of goblet cells (loss of maturation). The neoplastic cells have large, elongated, hyperchromatic nuclei. E. There are increased mitotic figures (long arrow) and presence of single cell necrosis (short arrow).

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View Figure  		Fig. 5  A so-called colonic adenoma of 2 cm in size (the same lesion illustrated in Fig. 4). A: A pedunculated polypoid lesion. B: There is marked elongation of the crypts, parallel to each other. Goblet cells are decreased in number. C, D: The neoplastic cells having large hyperchromatic nuclei. Mitotic figures are increased and are even seen at the surface of the crypts.