Immunohistochemically detectable duct-like structures in benign and malignant eccrine poromas: CEA and involucrin...

The duct-like structures present in 7 cases of benign and malignant eccrine poroma were examined by immunohistochemical staining for carcinoembryonic antigen (CEA), involucrin, and S-100 protein. The demonstration of CEA and involucrin was helpful in the recognition of these structures. The overt immunopositivity precedes morphological evidence for duct formation. On the basis of the CEA immunostaining, the duct-like structures were divided into 4 types: 1) mature acrosyringeal structure, 2) cystic luminal structure lined by elongated cells, 3) immature acrosyringeal structure, and 4) vacuole- or dot-like potential lumen in a single cell. Involucrine was observed in the lining cells of 1) and 2). None of the 4 types showed positive reactivity for S-100 protein, suggesting the irrelevance of these structures to the secretory element of sweat gland. The polymorphism of the ductal formation tended to be more remarkably observed in malignant eccrine poromas than in the cases of benign eccrine poroma and poroepithelioma tested.