ABSTRACT
<p><b>OBJECTIVE</b>To study the clinicopathologic features and differential diagnosis of 18 cases of endocrine ductal carcinoma-in-situ (E-DCIS).</p><p><b>METHODS</b>Eighteen cases of breast cancer with features of E-DCIS were studied by light microscopy, histochemistry and immunohistochemistry. E-DCIS was diagnosed if the histologic patterns were compatible with those described in the literature and at least 50% of the tumor cells expressing two of the three neuroendocrine markers employed (chromogranin, synaptophysin and neuron-specific enolase).</p><p><b>RESULTS</b>E-DCIS tended to occur in older women. All the patients were over 61 years old (mean age=71 years). The presenting symptoms were either palpable breast mass or had nipple discharge. Histologically, E-DCIS demonstrated an expansile intraductal growth pattern. Intraductal papilloma was not uncommon at the peripheral area of the tumor. The tumor cells were polygonal, oval or spindle in shape and contained abundant eosinophilic to granular cytoplasm and mildly to moderately pleomorphic nuclei. Intracellular or extracellular mucin was highlighted by periodic acid-Schiff (with diastase digestion) or alcian blue stains. Some tumor cells assumed a signet-ring configuration. All the three neuroendocrine markers were expressed by more than 50% of the E-DCIS cells. The neuroendocrine differentiation was further confirmed in some cases by CD57 and CD56 immunostaining. Pagetoid spread into adjacent ductolobular units was frequently seen in E-DCIS, and the expanded lobules were often not rimmed by myoepithelial cells. These two features helped to distinguish E-DCIS from usual ductal hyperplasia.</p><p><b>CONCLUSIONS</b>E-DCIS represents a subgroup of low-grade DCIS, which carries characteristic morphologic features and immunophenotype. Conventional light microscopy usually permits a correct diagnosis. Ancillary histochemical and immunohistochemical studies can be helpful in doubtful cases.</p>