In most cases, small-cell carcinoma of the urinary bladder is admixed with other histological types of bladder carcinoma. To understand the pathogenetic relationship between the two tumor types, we analyzed histologically distinct tumor cell populations from the same patient for loss of heterozygosity (LOH) and X chromosome inactivation (in female patients). We examined five polymorphic microsatellite markers located on chromosome 3p25-26 (D3S3050), chromosome 9p21 (IFNA and D9S171), chromosome 9q32-33 (D9S177), and chromosome 17p13 (TP53) in 20 patients with small-cell carcinoma of the urinary bladder and concurrent urothelial carcinoma. DNA samples were prepared from formalin-fixed, paraffin-embedded tissue sections using laser-assisted microdissection. A nearly identical pattern of allelic loss was observed in the two tumor types in all cases, with an overall frequency of allelic loss of 90% (18 of 20 cases). Three patients showed different allelic loss patterns in the two tumor types at a single locus; however, the LOH patterns at the remaining loci were identical. Similarly, the same pattern of nonrandom X chromosome inactivation was present in both carcinoma components in the four cases analyzed. Concordant genetic alterations and X chromosome inactivation between small-cell carcinoma and coexisting urothelial carcinoma suggest that both tumor compo- Small-cell carcinoma of the urinary bladder histologically resembles that occurring in the lung and has been reported with an increasing frequency in recent years. [1][2][3][4][5][6][7][8][9][10] It has been estimated to represent 0.5% of bladder malignancies and develops more frequently in older men, with hematuria as the most common presenting symptom. 8 Small-cell carcinoma of the urinary bladder behaves aggressively, often with locally advanced or metastatic disease at the time of presentation. 11 Over the years, three principal theories have been proposed to account for the development of small-cell carcinoma in the urinary bladder. The first theory is that small-cell carcinomas originate from multipotential, undifferentiated cells or stem cells in the urothelium. 5,8,12,13 The frequent association of this tumor with coexisting urothelial carcinoma supports this theory. The second theory is that these tumors arise from neuroendocrine cells within normal or metaplastic urothelium. 14 The third theory is that small-cell carcinomas are derived from an undefined population of submucosal neuroendocrine cells. 1 In this study, we investigated the clonal relationships between small-cell carcinoma and coexisting urothelial carcinoma using loss of heterozygosity (LOH) and X chromosome inactivation analysis. Materials and Methods PatientsTwenty patients with small-cell carcinoma of the urinary bladder and concurrent urothelial carcinoma were included in our study. Archival materials from the 20 cases

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Purpose: Patients with papillary thyroid carcinoma often have two or more distinct papillary tumors at thyroidectomy. Whether these multifocal papillary lesions are clonally related or whether they arise independently is unknown as previous studies have shown conflicting results. Molecular analysis of microsatellite alterations and X-chromosome inactivation status in separate tumors from the same patient can be used to define the genetic relationships among the multiple coexisting tumors. Experimental Design: We examined 64 separate tumors from 22 female patients who underwent thyroidectomy for thyroid carcinoma. All patients had multiple and separate papillary carcinomas (range, two to six). Genomic DNA samples were prepared from formalin-fixed, paraffin-embedded tissue sections using laser-capture microdissection. Loss of heterozygosity assays for three microsatellite polymorphic markers for putative tumor suppressor genes on chromosomes 3p25 (D3S1597), 9p21 (D9S161), and 18p11.22-p11 (D18S53) were done. In addition, X-chromosome inactivation analysis was done on the tumors from all patients. Results:Twenty of 22 (91%) cases showed allelic loss in one or more of the papillary lesions in at least one of the three polymorphic markers analyzed. Concordant allelic loss patterns between coexisting papillary tumors were seen in 20 of 23 (87%) cases. A concordant pattern of nonrandom X-chromosome inactivation in the multiple coexisting papillary lesions was seen in all informative cases. Conclusion: Our data suggest that the multifocal tumors in patients with papillary thyroid carcinoma often arise from the same clone. Thus, intrathryoid metastasis may play an important role in the spread of papillary thyroid carcinoma, a finding that has important therapeutic, diagnostic, and prognostic implications.Papillary thyroid carcinoma is the most common malignancy of the adult thyroid with an average of 20,000 new cases occurring each year. These tumors often present as thyroid nodules or as lymphadenopathy due to metastases (1, 2). Papillary thyroid carcinoma is frequently seen in the setting of Hashimoto's thyroiditis and is more frequently multifocal than any other well-characterized type of thyroid carcinoma. Often, there is a primary tumor that is >1 cm and additional microscopic foci measuring <1 cm (3, 4). Multifocal tumors have been associated with an increased risk of lymph node and distant metastases, suggesting multifocal papillary thyroid cancer may necessitate a unique treatment approach (5).Previous genetic studies have shown follicular thyroid carcinomas to display more extensive loss of heterozygosity and increased chromosomal instability than papillary carcinomas, which may be responsible for the more indolent course and better prognosis of papillary lesions (6 -8). The RET, NTRK1, RAS, and BRAF genes have been shown to participate in the pathogenesis of papillary thyroid carcinoma (9 -18). Subsequent clonality studies have yielded variable results, with independent clonal origin of multifocal papi...

Phyllodes tumor of the prostate is a rare neoplasm, composed of epithelium-lined cysts and channels embedded in a variably cellular stroma. The pathogenetic relationship of the epithelium and stroma is unknown and whether each is a clonal neoplastic element is uncertain. We studied the clonality of phyllodes tumors from six patients who underwent either enucleation or transurethral resection as their initial treatment. This was followed by total prostatectomy in three of the patients. Laser-assisted microdissection was performed to extract epithelial and stromal components of phyllodes tumor from formalin-fixed, paraffinembedded tissue. Polymerase chain reaction was used to amplify genomic DNA at specific loci on chromosome 7q31 (D7S522), 8p21.3-q11.1 (D8S133, D8S137), 8p22 (D8S261), 10q23 (D10S168, D10S571), 17p13 (TP53), 16q23.2 (D16S507), 12q11-12 (D12S264), 17q (D17S855), 18p11.22-p11 (D18S53), and 22q11.2 (D22S264). In each tumor, stroma and epithelium were analyzed separately. Gel electrophoresis with autoradiography was used to detect loss of heterozygosity. All tumors showed allelic loss in one or more loci of both the epithelial and stromal components. The frequency of allelic loss in the epithelial component was 2 of 5 (40%) at D7S522, 2 of 6 (33%) at D8S133, 1 of 5 (20%) at D8S137, 3 of 6 (50%) at D8S261, 4 of 4 (100%) at D10S168, 4 of 6 (67%) at TP53, 2 of 6 (33%) at D10S571, 6 of 6 (100%) at D16S507, 1 of 5 (20%) at D12S264, 1 of 6 (17%) at D17S855, 2 of 6 (33%) at D18S53, and 2 of 5 (40%) at D22S264. The frequency of allelic loss in the stromal component was 2 of 5 (40%) at D7S522, 1 of 6 (17%) at D8S133, 2 of 5 (40%) at D8S137, 3 of 6 (50%) at Phyllodes tumor of the prostate is a rare neoplasm with poorly understood pathogenesis. Histologically, it resembles phyllodes tumor of the breast with hyperplastic epithelium-lined cysts and channels embedded in a variably cellular stroma.1,2 A variety of terms have been used to describe these lesions, including phyllodes type of atypical hyperplasia, cystosarcoma phyllodes, and prostatic cystic epithelial-stromal tumor.

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