Sporadic Adenomas vs Dysplasia Associated Lesion Mass DALM

Several different subtypes of DALMs in IBD have been described. These subtypes broadly fall into two forms, adenoma-like and non-adenoma like. This distinction is based primarily on their gross/endo-scopic appearance. Non-adenoma-like lesions are usually large, sessile with a broad base, irregular masses or ill-defined nodules. To some, a biopsy finding of dysplasia in a non-adenoma-like DALM, either low or high-grade, is usually an indication for colectomy because of the high probability (between 30 to 80%) of an associated adenocarcinoma [14]. Adenoma-like DALM is present as an isolated, well-circumscribed and pedunculated adenoma-like polypoid dysplastic lesion, which is basically not unlike the appearance of a sporadic adenoma either endo-scopically or macroscopically. In this instance, the clinical differential diagnosis includes an adenomalike DALM in UC vs. a sporadic adenoma, a lesion that occurs coincidentally in a patient with underlying IBD.

The fact that sporadic adenomas can also arise within colons affected by IBD creates a problem in diagnosis and management. Sporadic adenoma arising in patients with IBD can sometimes be difficult if not impossible to differentiate from IBD-associated dysplasia (polypoid dysplasia). One can be confident that one is dealing with a sporadic adenoma if it is found in an area not affected by IBD (a right-sided adenoma in a patient with left-sided colitis). On the other hand, finding such a lesion in a colonic segment affected by IBD in a young age group is in favour of polypoid dysplasia rather than adenomas, as these tend to occur mostly in a middle age group or older. However, if the adenoma-like dysplastic lesion arises within an area involved by IBD, then this problem becomes much more difficult. It used to be recommended to 'judge the lesion by the company of the epithelium it keeps'. In other words, if the epithelium adjacent to the lesion is dysplastic, then the lesion is judged to be the same. We feel that is a feeble way of addressing the issue scientifically.

In an attempt to distinguish sporadic adenomas from adenoma-like dysplastic lesions arising in IBD, studies have evaluated as to whether histologic features [23], molecular genetic studies or the location of the lesion can be used reliably to distinguish between them. Torres et al. [24] evaluated 89 polypoid adenomatous lesions from 59 patients with IBD, including 51 patients with UC and 8 patients with CD, and correlated the morphologic features of these adenoma-like lesions with clinical, endoscopic and follow-up data. If the lesion was located proximal to histologically diseased mucosa, lesions were classified as A, or probable sporadic adenomas. If they developed within an area of colitis associated with flat dysplasia or carcinoma, which was detected during follow-up, lesions were classified as B, or probable IBD-associated polypoid dysplasia. If they were located in an area of colitis, but with no flat dysplasia or carcinoma on the follow-up evaluation, the lesions were classified as C, or indeterminate type. In nine patients with probable sporadic adenomas (group A), follow-up information was available and none developed subsequent dysplasia or adenocarcinoma. In contrast, of the 31 patients with either indeterminate polyps or probable IBD-associated dysplastic lesions (groups B and C), in the follow-up information, 13 patients either had or developed flat dysplastic lesions or adenocarcinoma in adjacent mucosa (including five patients with probable IBD-associated dysplastic lesions who had flat dysplasia in adjacent mucosa at the onset). Using these categories, it was found that patients with probable IBD-associated dysplastic lesions were younger (median age 48 years) than those with probable sporadic adenomas (median age 63.5 years), were more likely to have active colitis and were more likely to have a longer duration of disease (median 11 vs. 5 years). Histologically, patients with probable IBD-associated dysplastic lesions more commonly had lamina propria mononuclear inflammation, lamina propria neutrophilia and most importantly, were significantly more likely to have an admixture of dysplastic and non-dysplastic crypts on the surface of the polyp (60 vs. 16%). Others suggest that superficial, or the so-called "top down", dysplasia is more specific for a subset of adenoma-like polyps. In such lesions, the dysplastic glands are usually located in the upper part of the polyp and confined to the surface, forming a band like array [13].

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Responses

  • hassan
    How to distinguish dalm from sporadic adenoma?
    8 years ago
  • bonnie wood
    How to differentiate DALM from adenoma?
    4 years ago

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