Papillary lesions These lesions cause diagnostic problems because papillary structures are found in benign and malignant processes and the differences between the two are often subtle and difficult to assess; the entities concerned are shown in Table 3. In practice few problems should be encountered with small single benign intraduct papillomas which are usually centrally placed under the nipple and removed by microdochectomy. However, potential pitfalls will be encountered with all of these processes on needle core biopsy, partly because of sampling error and partly related to architectural distortion due to crush artefact. Our early experience with pre-operative use of needle core biopsy, based on the manual Tru-Cut needle lead us to advise caution when benign papillary structures were identified, because of the risk of a false negative diagnosis. It is undoubtedly true that some invasive papillary carcinomas arise in a pre-existing benign papilloma, almost always of the multiple type. The finding of benign papillary structures on needle core biopsy does not necessarily mean, therefore, that malignant change is not present elsewhere in the lesion. It is our practice to issue a report with a non-specific conclusion of 'papillary lesion present', and local excision is advised. This would come into the B3 category - lesion of uncertain malignant potential - in the revised United Kingdom National Health Service Breast Screening Service (NHSBSP) Guidelines for Pathologists. It should also be noted that multiple duct papillomas are usually peripheral and often associated with florid epithelial proliferations, including usual and atypical ductal hyperplasia. In excision specimens adequate sampling is required to exclude the presence of associated ductal carcinoma in situ (see also below - borderline lesions). Some benign papillary lesions form relatively well defined solid masses with a dominantly sclerosed architecture. In the past the term ductal adenoma was applied to such lesions, but they are now believed to arise from sclerosis of duct papillomas and we prefer to use the term complex sclerosing papillary lesion. Epithelial proliferation is relatively common and a minor degree of nuclear atypia may be seen, especially if there is apocrine change. They are, in fact, entirely benign and care must be taken not to overdiagnose malignancy, especially if entrapped tubular structures are found. There is considerable morphological overlap with sclerosing adenosis and radial scar/complex sclerosing lesion and in some cases it may be impossible to make a firm distinction. Encysted papillary carcinoma (papillary carcinoma in situ) may be confused with invasive papillary carcinoma, especially on needle core biopsy. This relatively uncommon lesion is now being detected with increasing frequency in mammographic screening. Because of their soft, cystic structure encysted papillary carcinomas are rarely palpable clinically, but are seen on mammography in older women as well circumscribed mass lesions. Astute radiologists quickly develop a suspicion of the correct diagnosis when they encounter an unusual degree of haemorrhage on needling the lesion. Using a multi-disciplinary team approach this information enables the pathologist to assess the papillary structures seen on needle core biopsy more accurately. The presence of multi-layering and genuine cytological atypia point towards a diagnosis of encysted papillary carcinoma rather than a benign intracystic papilloma but care must be taken not to overinterpret the presence of entrapped tubules as evidence of invasion. In any event all such circumscribed impalpable papillary lesions should be managed by complete local excision rather than mastectomy in the first instance. Attention must be paid to excision margins, since local recurrence is related both to the presence of ductal carcinoma in situ in adjacent ductal structures and completeness of excision. 18 As with needle core biopsy areas of possible invasion around the periphery of the excised lesion should be assessed with caution. There is usually a broad fibrous 'capsule' and 'pseudoinvasion' due to the presence of entrapped tubules is a frequent finding. Invasive carcinoma may, rarely, be associated with encysted papillary carcinoma, but should only be diagnosed when epithelial structures extend into adjacent breast or adipose tissue. Encysted papillary carcinoma has a good prognosis and complete excision appears to be curative. 18 |
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