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Solitary fibrous tumors are spindle-cell neoplasms that originally were described in the pleura but that can occur in a large variety of sites. We report a well-circumscribed tumor, apparently involving the renal capsule, clinically thought to be a renal-cell carcinoma or oncocytoma. It was composed of bland spindle-shaped cells with a patchy lymphoplasmacytic infiltrate, suggesting sarcomatoid renal-cell carcinoma, inflammatory myofibroblastic tumor, or solitary fibrous tumor; however, immunohistochemical stains were negative for keratin, alpha-smooth-muscle actin, and desmin but strongly positive for CD34. Ultrastructural examination revealed fibroblast-like cells without myofibroblastic or epithelial differentiation. The combined findings favor a diagnosis of a solitary fibrous tumor involving the renal capsule. To our knowledge, this lesion has not been reported in this location.

Primary lymphoma of the colon, a rare and typically late complication of ulcerative colitis, exhibits high-grade morphology and behavior when it occurs. Recently, several reports of colonic lymphoma masquerading as ulcerative colitis have been described. These previous reports described inflammatory mucosal changes typical of ulcerative colitis as being present in superficial biopsies, leading to the initial diagnosis of ulcerative colitis; however, further workup resulted in a diagnosis of primary colonic lymphoma within several months in these cases, and all symptoms and mucosal changes resolved after treatment of the lymphoma. Herein we report a case of mantle cell lymphoma arising in the colon and rectum in a 71-year-old woman with a 4-year history of ulcerative colitis. Immunoglobulin heavy-chain gene rearrangements were detected using the polymerase chain reaction procedure in fixed tissue in the lymphoma as well as in a prior resection specimen that histologically appeared to show only changes of severe ulcerative colitis. This finding suggests that an indolent lymphoid proliferation may have been the underlying disease in this patient and raises questions about the role of colonic lymphoma in causing mucosal injury.

Ewing's sarcoma (ES) and peripheral neuroepithelioma (PN) are closely related tumors, and it can be difficult to distinguish them from other small-round-cell tumors (SRCTs). The glycoprotein p30/32MIC2 is highly, but not exclusively, expressed in both ES and PN. Although the monoclonal antibody (Mab) HBA71, which reacts with P30/32MIC2, has been reported to be relatively specific and highly sensitive for both neoplasms, it is not readily available. Yet, Mab O13 is commercially available, and it purportedly displays the same immunostaining characteristics as HBA71. Because O13 has not been studied extensively, we immunostained 21 ES/PNs and 147 other tumors or lesions that might show SRCT-like features with O13. The results were similar to those reported for HBA71. We found O13 to be 100% sensitive for ES/PN; and, no immunostaining was noted on the SRCTs often included in the differential diagnosis of ES/PN (i.e., conventional neuroblastoma, rhabdomyosarcoma, and non-lymphoblastic lymphomas). But, O13 immunoreacted with lymphoblastic lymphomas and some other tumors and normal tissues. Nonetheless, this nonspecific reactivity should not cause diagnostic problems, if an antibody panel containing anti-desmin and anti-leukocyte common antigen is used in conjunction with O13. We conclude that, within the proper diagnostic context, strong immunoreactivity of a SRCT tumor for O13 should be considered good evidence that the tumor is ES/PN.

Tumor proliferation is inversely associated with survival in patients with breast carcinoma. Labeling of tumor cells with bromodeoxyuridine (BRDU) correlates highly with that seen with [3H]thymidine, the current "gold standard" for measuring tumor S-phase. However, the relationship of BRDU labeling to mitotic figure content and tumor grade remains incompletely defined. To determine this, we labeled 55 breast carcinomas with BRDU in vivo and correlated the results with mitotic figure content. The BRDU labeling index was the number of BRDU-positive cells/2,000 tumor cells, the mitotic figure index was the number of mitotic figures per 1,000 tumor cells, and the mitotic figure count was the number of mitotic figures per 10 high-powered fields. BRDU labeling was also correlated with tumor grade (Scarff-Bloom-Richardson). The BRDU labeling index correlated highly with the mitotic figure index (r = 0.814, p = 7.0 x 10(-14)), mitotic figure count (r = 0.725, p = 6.0 x 10(-10)), and tumor grade (r = 0.68, p = 1.1 x 10(-8)). The correlation of BRDU labeling with mitotic figure content was strong enough to suggest that a very carefully measured mitotic figure index provides an estimate of tumor growth fraction equivalent to the BRDU labeling index. Also, analysis of variance showed that the mitotic figure index was twice as precise as the mitotic figure count in estimating BRDU labeling, and thus was a more accurate measure of tumor proliferation. Moreover, measurements made by the mitotic figure index were as precise as those made by BRDU labeling. However, which method is optimal for estimating tumor proliferation rate remains unclear. Further studies are indicated.

We describe a unique case of pure squamous carcinoma of the larynx that developed a cervical lymph node metastasis showing rhabdomyosarcoma admixed with squamous carcinoma (that is, carcinosarcoma). The rhabdomyosarcoma showed foci immunoreactive to multiple cytokeratin monoclonal antibodies, as well as to markers for striated muscle, thus indicating true divergent epithelial and rhabdomyosarcomatous differentiation. Although the morphogenesis of carcinosarcomas remains controversial, the sequence of events for the current case favors sarcomatous transformation of the original carcinoma (that is, sarcomatous neometaplasia of the primary carcinoma clone). The possible contributory role of radiation therapy in this case in inducing such a change is noted.

Nucleolar organizer regions (NOR) are DNA loops encoding ribosomal RNA production. Detectable by the argyrophilia (AgNOR) of associated proteins, AgNOR numbers correlate with growth fraction and may have diagnostic and prognostic utility in human tumors. Because nucleolar size is important in the diagnosis of prostate carcinoma, we compared AgNOR counts in benign, atypical, and malignant prostate lesions and correlated them with nucleolar diameter. We counted AgNOR in benign prostatic hyperplasia, atypical adenomatous hyperplasia, intraductal dysplasias, and carcinomas of various Gleason grades. The mean AgNOR count per nucleus for benign prostatic hyperplasia nuclei was 4.51; for atypical adenomatous hyperplasia, 5.64; for intraductal dysplasias, 7.35; for carcinoma of Gleason grades 2 + 3, 8.87; and for carcinoma Gleason grades 4 + 5, 10.42. Counts in the carcinomas and intraductal dysplasias were significantly different from those of benign prostatic hyperplasia. Mean AgNOR counts of the carcinomas and intraductal dysplasias did not overlap with those of benign prostatic hyperplasia, suggesting that intraductal dysplasia shares more with carcinoma than benign prostatic hyperplasia. Nucleolar diameters increased from benign prostatic hyperplasia to atypical adenomatous hyperplasia, intraductal dysplasias, and the carcinomas, correlating with increasing AgNOR counts. Nucleolar diameters in the carcinomas were significantly different than those of benign prostatic hyperplasia; those in intraductal dysplasias were not. Our findings suggest that AgNOR counts are superior to nucleolar diameters alone in separating intraductal dysplasias from benign prostatic hyperplasia but provide no additional information in diagnosing carcinoma.

Peptic ulceration is a known complication of hepatic arterial chemotherapy for metastatic disease. We report a case of peptic ulceration associated with marked epithelial atypia initially interpreted as carcinoma, probably metastatic in nature. Subsequent partial gastric resection proved the lesion benign. Examination of other gastric biopsies from ulcerated and nonulcerated mucosa from similarly treated patients has revealed similar marked atypical changes. The etiology of the epithelial atypia and ulceration remains unanswered, but is probably related to locally enhanced chemotherapeutic cytotoxicity or ischemia. Care should be taken not to interpret the marked epithelial atypia as carcinoma in this clinical setting.

Two unusual cases of colonic ganglioneuromatosis are described. One case was associated with multiple adenomatous polyps in a 74-year-old man and the second case was associated with juvenile polyps in a 16-year-old boy. To our knowledge this is the first report of colonic mucosal ganglioneuromatosis associated with multiple adenomatous polyps and the second report associated with multiple juvenile polyps. In the first case the ganglioneuromatosis was found in colonic mucosa without adenomatous changes, while in the second case ganglioneuromatosis was found both within normal mucosa and within juvenile polyps. The relationship between mucosal ganglioneuromatosis and multiple colonic polyps remains unclear. Neither patient has yet developed features to suggest either multiple endocrine neoplasia type 2b or von Recklinghausen's disease.