The presence of K-ras point mutations defines a subgroup of patients with lung adenocarcinoma in whom the prognosis is very poor and disease-free survival is not usually long despite radical resection and a small tumor load.

Amplification of the neu proto-oncogene in breast cancer has been reported to correlate with the presence of lymph-node metastases and with a poor prognosis. We describe a method for the immunohistochemical detection of overexpression of neu protein on formalin-fixed paraffin-embedded tissue, with the use of two different monoclonal antibodies. In a group of tumors with a known neu-gene copy number, intense membrane staining of tumor cells was present in all tumors with neu-gene amplification. Of 189 tumors from patients with Stage II breast cancer, 27 (14 percent) had neu-membrane staining. Neu overexpression was associated with larger tumor size (P = 0.006) but not with lymph-node involvement. Neu-protein expression in lymph-node metastases was the same as its expression in primary tumors. Among the patients with neu overexpression (median follow-up, 37 months), disease-free survival was not significantly shorter; overall survival was reduced significantly in these patients (P = 0.042), but this reduction did not remain significant after adjustment for tumor size. Of 45 ductal carcinomas in situ, 19 (42 percent) had neu-membrane staining. These 19 were all of the large-cell, comedo growth type. None of 16 ductal carcinomas in situ of small-cell, papillary, or cribriform growth type had neu overexpression. We conclude that neu overexpression may be an early step in the development of a distinct histologic type of carcinoma of the breast, but we could find no association of overexpression with lymph-node status or tumor recurrence.

nal intensities on T1-and T2-weighted images, contrast enhancement, relationship with adjacent fascia or tendon, secondary bone involvement, and intratumoral necrosis. In 19 cases the pathology findings were available for review and for a comparative MR-pathology study.Results. On T1-weighted images, lesions were isointense (n=3), hypointense (n=7) or slightly hyperintense to muscle (n=11). Immunohistochemical examination was performed in 17 patients. All 17 specimens showed positivity for HMB-45 antibody. In nine of 11 lesions with slightly increased signal intensity on T1-weighted images, a correlative MR imaging-pathology study was possible. All nine were positive to HMB-45 antibody. Conclusions. Clear cell sarcoma of the musculoskeletal system often has a benign-looking appearance on MR images. In up to 52% of patients, this lesion with melanocytic differentiation has slightly increased signal intensity on T1-weighted images compared with muscle. As the presence of this relative higher signal intensity on T1-weighted images is rather specific for tumors displaying melanocytic differentiation, radiologists should familiarize themselves with this rare entity and include it in their differential diagnosis when confronted with a well-defined, homogeneous, strongly enhancing mass with slightly higher signal intensity compared with muscle on native T1-weighted images. Abstract Objective. To evaluate MR imaging and pathology findings in order to define the characteristic features of clear cell sarcoma of the soft tissues (malignant melanoma of the soft parts). Design and patients. MR examinations of 21 patients with histologically proven clear cell sarcoma of the musculoskeletal system were retrospectively reviewed and assessed for shape, homogeneity, delineation, sig- Key words

Three infants with clinical and biochemical features of Zellweger's cerebrohepatorenal syndrome are presented, and the ultrastructural features of successive biopsy and autopsy liver specimens are described. No hepatocellular peroxisomes were found in these patients on routine electron microscopy or electron microscopic histochemistry. In a control group of liver biopsies from 9 patients with other pediatric liver diseases, peroxisomes were readily identifiable in each hepatocyte. Apart from the absence of peroxisomes, the hepatocytes had a remarkably "normal" aspect, even in the final stages of the disease. Mitochondrial abnormalities, which have been the subject of some controversy in this syndrome, were a highly variable and inconstant finding in our cases. We draw attention to another ultrastructural feature of the syndrome, namely the occurrence of large angulate lysosomes, containing conspicuous double lamellae, inside macrophages, which were especially abundant in later stages of the disease. These angulate lysosomes may be of additional value in the ultrastructural diagnosis of Zellweger's syndrome, especially when only poorly preserved liver tissue (e.g., paraffin-embedded or postmortem material) is available, and the absence of peroxisomes is difficult to assess. In these instances, the angulate lysosomes can still be identified with ease.

Atrophy of the external anal sphincter can be shown only on endoanal magnetic resonance imaging (MRI). Until now no study has compared the morphological endoanal MRI findings with histopathological aspects of the external anal sphincter. The aim of this study was to validate the MRI interpretation of the external anal sphincter using histology as a "gold standard." In this prospective study 25 consecutive unselected women (median age 48 years, range 27-72) with fecal incontinence due to obstetric trauma were assessed preoperatively with endoanal MRI. All patients underwent anterior sphincteroplasty within 6 months of the preoperative assessment. During sphincter repair, a biopsy specimen was taken both from the left and right lateral parts of the external anal sphincter. Interpretation of MRI was performed by one of the radiologists (J.S.), and biopsy specimens were evaluated by the pathologist (W.J.M.). Both were blinded to the interpretation of the other. MRI revealed external anal sphincter atrophy in 9 of the 25 patients (36%). Histopathological investigation confirmed these findings in all but one. In one additional patient atrophy was detected on histological investigation while the morphology of the external anal sphincter was classified as normal on MRI. In detecting sphincter atrophy endoanal MRI showed 89% sensitivity, 94% specificity, 89% positive predictive value, and 94% negative predictive value. MRI correctly identified sphincter morphology in 23 of 25 cases (92%). This study demonstrates that endoanal MRI accurately identifies normal and abnormal external anal sphincter morphology. Endoanal MRI is therefore a valuable preoperative diagnostic tool.

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