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Background Porocarcinomas are rare aggressive carcinomas that harbor tumor suppressor mutations and must be distinguished from benign entities such as poromas. Methods To determine whether altered expression of these genes was diagnostically informative, we examined p53, Rb, and p16 staining patterns in 15 poromas and 16 porocarcinomas. Results Poromas consistently displayed diffuse strong expression of Rb in all but one case that displayed focal loss (1/15, 7%), and no evidence of aberrancy in p53 or p16. Porocarcinomas displayed diffuse or focal loss of Rb expression in 9/16 (56%) cases, diffuse loss or overexpression of p53 in 8/15 (53%), and diffuse loss or overexpression of p16 in 6/14 (43%). Diffuse aberrancy in p53 and Rb expression correlated with tumor mutations in TP53 and RB1, respectively, whereas focal Rb loss was associated with wild type RB1. Diffuse p16 overexpression correlated with Rb loss rather than CDKN2A mutation. For porocarcinomas with all three stains evaluable, 10/13 (77%) displayed aberrancy in at least one marker. Conclusions Our findings suggest that altered p53, p16, and/or Rb expression is relatively specific to porocarcinoma in comparison with poroma. Technical limitations of this panel, including possible focal Rb loss, must be kept in mind, especially in limited samples.

Berlyne's stimuli were presented in a stereoscope to test his hypothesis that Ss prefer the more irregular member of a pair of stimuli. 32 Ss, screened for normal acuity and phorias, were tested. Contrary to Berlyne's hypothesis and consistent with earlier stereoscopic studies, Ss tend to report more frequently the less irregular member of a pair of stimuli. These data can be explained by an information-conflict model; however, the clearest implication of this study was that experiments concerned with familiarity of stimuli should be qualified by the method.

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