Mucin histochemistry in primary adenocarcinoma of the urinary bladder (of urachal or vesicular origin) and metastatic adenocarcinoma originating in the colorectum.

In order to evaluate the mucin histochemistry of primary adenocarcinomas (PA) of the urinary bladder and metastatic adenocarcinoma (MA) originating in the colorectum, 52 PA and nine MA were examined. It was determined that the percentage of cases in which more than 25% of the tumor was stained by each of the following: (i) Alcian blue pH 2.5 periodic acid–Schiff (AB-PAS); (ii) high iron diamine-AB (HID-AB); (iii) periodic acid-sodium borohydride-potassium hydroxide-PAS (PA-SB-PH-PAS); (iv) galactose oxidase– Schiff (GOS); and (v) paradoxical concanavalin A stain (PCS). For PA, the values obtained were: 75% of cases (blue, AB-PAS), 85% (magenta, AB-PAS), 71% (black, HID-AB), 75% (blue, HID-AB), 0% (PA-SB-PH-PAS), 19% (GOS), 8% (class II concanavalin A (Con A)-reactive mucin)), and 0% (class III Con A-reactive mucin). For MA, the corresponding values were 33, 22, 0, 11, 0, 0, 11, and 0%, respectively. A higher percentage of PA than MA cases showed staining in AB-PAS for acidic and neutral mucins, in HID-AB for sialo- and sulfomucins, and in GOS for terminal β-galactose and β-N-acetylgalactosamine. PA and MA were significantly different in terms of both frequency of staining with AB-PAS and frequency of staining with HID-AB. However, the overlap was such that in practice, it might be difficult, if not impossible, to use mucin histochemistry to inform a differential diagnosis. In view of the differences in AB-PAS and HID-AB positivity between PA and MA, we speculate that MA (originating in the colorectum) may have undergone structural distortion affecting the production and/or secretion of neutral mucins and acidic mucins (sialo- and sulfomucins) during metastasis or invasion.