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Clinicopathologic data including immunophenotypic expression of 16 new cases of small intestinal leiomyosarcoma are presented. Patient age ranged from 27 to 87 years (mean, 61 years) with a 2.2:1 male-female ratio. Eighty-eight percent of tumors occurred distally, i.e., in the jejunoileum. Considerable histologic heterogeneity was noted including epithelioid, myxoid, and sclerotic variants. Stratification by histologic grade suggests important clinical subsets. Only in grade I tumors is surgical extirpation alone potentially curative. Grade II tumors are associated with meaningful survival usually measured in years, however, nearly all patients can be expected to die from their tumors. Grade III sarcomas are fully malignant and rapidly progressive: except for one case with limited follow-up, all patients with Grade III sarcomas died of disease with a mean survival of only nine months (median, 2 months). Immunostaining with antibodies directed against vimentin, muscle-specific actin, desmin, and S-100 protein were performed. Only antivimentin was uniformly reactive. Sixty-three percent of cases tested showed actin immunoreactivity, and no tumors revealed immunohistochemically detectable desmin or S-100 protein. Although many small bowel stromal sarcomas appear "poorly differentiated" by immunohistochemical methods presently available, that they are indeed leiomyosarcomas seems most likely from their intramural location and light histologic study. The limited utility of immunophenotyping and the importance of histologic grading are stressed.

Albumin messenger RNA (mRNA) in situ hybridization is a sensitive and specific biomarker for hepatocellular carcinoma (HCC). Intrahepatic cholangiocarcinoma (ICC) shows variable sensitivity, whereas extrahepatic cholangiocarcinoma (ECC) and metastatic carcinoma are generally negative. We studied the clinical utility and limitations of albumin mRNA detection in a cohort of HCCs, ICCs, ECCs, bile duct adenomas, bile duct hamartomas, and metastatic carcinomas to the liver; and investigated the variability in sensitivity observed for this biomarker in ICCs. We identified 122 cases of hepatobiliary lesions and metastatic carcinomas. Albumin mRNA detection was performed using RNAscope run on formalin-fixed, paraffin-embedded tissue sections. ICCs were categorized according to the classification proposed by Hayashi and colleagues into the small duct, large duct, and indeterminate subtypes. Albumin mRNA was detected in all 17 HCCs and focally in 6/8 (75%) of bile duct adenomas. All 28 nonhepatic carcinomas, 13 bile duct hamartomas, and 9 ECCs were negative. Albumin mRNA was found in 38/47 (80.9%) of ICC with 35/37 (94.6%) in the small duct subtype, 2/3 (66.7%) in the indeterminate subtype, and 1/7 (14.3%) of the large duct subtype (P<0.003). Albumin mRNA detection is a sensitive and specific biomarker for HCCs. It is highly sensitive and moderately specific in the diagnosis of ICC with small gland morphology, but not ICCs with large duct morphology and in metastatic carcinoma. The variability in the sensitivity of albumin mRNA expression in ICCs may depend on the subtypes of ICC.

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