PAS and GMS stains are quantitatively similar. Sensitivity of both methods can be increased by preparing two slides from different levels in the paraffin block.

We report a case of biliary adenofibroma with an invasive carcinoma in a 71-year-old female who presented with bilateral upper abdominal pain. Imaging revealed a 6.3 cm heterogeneously enhancing mass in the left lateral segment of the liver. Histologically, the adenofibroma showed the characteristic components as previously described of biliary adenofibromata, namely, cystic and tubular structures lined by cuboidal to low columnar biliary type epithelium and a dense fibrous stroma composed of spindled cells. Intimately admixed with the adenofibroma was a distinct tumor composed of malignant clear cells which demonstrated stromal and vascular invasion. Although mitotic figures were inconspicuous, Ki67 was brisk and p53 demonstrated 25–50% positivity. Sections also showed a von Meyenberg complex located adjacent to the tumor. This case expands the understanding of this rare tumor and proves two important assertions from previous case reports. First, the presence of an associated von Meyenberg complex with similar morphology and immunohistochemical staining pattern suggests that biliary adenofibromata and von Meyenberg complexes may share related histogenesis. Second, biliary adenofibromata harbor malignant potential and may show malignant transformation. Furthermore, this case highlights the need for these rare tumors to be followed aggressively, as their biological behavior is poorly understood.

We present a case of a 61-year-old woman with end-stage renal disease (ESRD) who developed painless hematochezia following initiation of anticoagulation. Work-up revealed a large ulceration in the sigmoid colon, and histologic images revealed sevelamer crystals embedded in the colonic mucosa, consistent with sevelamer crystal-mediated injury. This is a novel cause of gastrointestinal hemorrhage that has not previously been described in the literature. Physicians should be aware of the potential for sevelamer-induced injury.

Peritoneal metastasis in colorectal carcinoma is associated with a dismal prognosis; however, features that correlate with patterns of metastatic spread are not well characterized. We analyzed the clinicopathologic and molecular features of 166 patients with colorectal carcinomas stratified by metastases to the peritoneum or liver. Mucinous and signet ring cell differentiation were more frequently observed in colorectal carcinoma with peritoneal dissemination compared to colorectal carcinoma with liver metastasis (mucinous differentiation: 62% vs 23%, P < .001; signet ring cell differentiation: 21% vs 0%, P < .0001). The significant association of mucinous differentiation with peritoneal dissemination compared with liver metastasis was identified in patients with both synchronous and metachronous development of metastasis ( P< .01). In contrast, colorectal carcinomas with liver metastasis were more frequently low-grade (90% vs 72%, P = .005) and associated with dirty necrosis (81% vs 56%, P = .001) compared with colorectal carcinomas with peritoneal dissemination. No significant differences were identified between colorectal carcinoma with peritoneal metastasis versus liver metastasis with respect to KRAS mutations, BRAF mutation, or high levels of microsatellite instability. Patients with tumors involving the peritoneum had a significantly worse overall survival in comparison to patients with liver metastasis lacking peritoneal involvement ( P = .02). When including only those patients with peritoneal metastasis, the presence of any mucinous or signet ring cell differentiation was associated with a significantly worse overall survival ( P = .006). Our findings indicate that mucinous and signet ring cell differentiation may be histologic features that are associated with an increased risk of peritoneal dissemination and poor overall survival in patients with peritoneal metastasis.