Genetic profile of cumulative mutational damage associated with early pulmonary adenocarcinoma: bronchioloalveolar carcinoma vs. stage I invasive adenocarcinoma.

To detect the possible genetic alterations characteristic of bronchioloalveolar carcinoma (BAC) and to study molecular genetic factors responsible for determining the biologic aggressiveness of pulmonary adenocarcinoma, comparative analysis of loss of heterozygosity (LOH) on 9 chromosomal regions was performed in 14 BACs and in 20 stage I adenocarcinomas (AD). The most frequently affected chromosome regions in BAC were 8q and 17p. In stage I AD, more than 60% of the cases showed LOH of 1p, 3p, 5q, 7q, 17p, and 18q loci, and LOH of 1p, 3p, 7q, and 18q was observed with greater frequency than in BAC (P < 0.05). Fractional allele loss (FAL) was significantly greater in stage I AD than in BAC (P < 0.001). In cases with microdissection of multiple sites, intratumoral heterogeneity of LOH status was observed in 73% of BAC and 94% of stage I AD, and homogeneous distribution of LOH of 9p was unique to BAC. The high FAL value was associated with a poor prognosis of BAC, but this trend did not reach statistical significance (P = 0.098). In stage I AD, no correlation was found between LOH of particular chromosomal region or FAL and clinical outcome. LOH of 1p, 3p, 7q, and 18q was associated with invasive properties of pulmonary AD and may be useful in identifying invasive adenocarcinoma when conventional histomorphological tools are not helpful.

Pulmonary meningothelial-like nodules: a genotypic comparison with meningiomas.

BACKGROUND: Minute pulmonary meningothelial-like nodules (MPMNs) are incidental interstitial pulmonary nodules. They share histologic, ultrastructural, and immunohistochemical features with meningiomas (MGs). DESIGN: Sixteen cases yielding 33 separate MPMNs and 10 cases of benign MG were studied. Immunohistochemical studies and mutational analyses were performed on microdissected tissue using 20 polymorphic microsatellite markers targeting 11 genomic regions in an effort to identify genetic similarities of MPMN and MG. RESULTS: A total of 96.6% of MPMNs stained positive for vimentin, 33.3% for epithelial membrane antigen, 3% for S-100, and all were negative for cytokeratin and synaptophysin. Loss of heterozygosity (LOH) was identified in 25% of single MPMN affecting 3 genomic loci. No solitary MPMN had more than 1 LOH event. Multiple LOHs were seen only in MPMN-omatosis syndrome, where 33.3% of MPMNs showed LOH affecting 7 genomic loci. MG showed the highest frequency of LOH with major events seen at 22q (60%), 14q (42.8%), and 1p (44.4%) that were not shared by MPMN. CONCLUSION: Isolated MPMN lacks mutational damage, consistent with a reactive origin. MPMN-omatosis syndrome might represent the transition between a reactive and neoplastic proliferation. MPMNs are different from MG based on the major molecular genetic events seen in their formation and progression.

Molecular analysis to demonstrate that odontogenic keratocysts are neoplastic.

CONTEXT: Odontogenic keratocysts (OKCs) are unique odontogenic lesions that have the potential to behave aggressively, that can recur, and that can be associated with the nevoid basal cell carcinoma syndrome. Whether they are developmental or neoplastic continues to be debated. OBJECTIVES: To identify loss of heterozygosity of tumor suppressor genes in OKCs and to suggest a pathogenetic origin for these lesions. DESIGN: We examined 10 OKCs for loss of heterozygosity of tumor suppressor genes, using a microdissection and semiquantitative genotyping analysis. The genes analyzed included 10 common tumor suppressor genes, as well as the PTCH gene, which is mutated in nevoid basal cell carcinoma syndrome. RESULTS: Loss of heterozygosity was seen in 7 of 10 cases, with a frequency between 11% and 80% of the genes studied. The genes that exhibited the most frequent allelic losses were p16, p53, PTCH, and MCC (75%, 66%, 60%, and 60%, respectively). Daughter cysts were associated with a higher frequency of allelic loss (P =.02), but epithelial budding was not. CONCLUSIONS: Our study indicates that a significant number of OKCs show clonal loss of heterozygosity of common tumor suppressor genes. The finding of clonal deletion mutations of genomic DNA in these cysts supports the hypothesis that they are neoplastic rather than developmental in origin.

Molecular genotyping of medullary thyroid carcinoma can predict tumor recurrence.

Medullary thyroid carcinoma can have an aggressive behavior, and little is known about the molecular basis for clinical outcome. Defining risk of recurrent or metastatic disease is difficult, and it has been limited to clinical and pathologic features, such as advanced age, cervical lymph node metastases, and stage at presentation. Using microdissection and genotyping, we studied 11 cases of medullary carcinoma for allelic losses in a panel of known tumor suppressor genes. The tumor suppressor genes with the most frequent allelic losses were NF2, l-myc, and p53 (75%, 44%, and 44%, respectively). The average frequency of allelic loss across all tumors was 44% and was higher in tumors that recurred. A combination of previously described high-risk variables (increased patient age and cervical lymph node metastases) with the frequency of allelic loss yielded a high-risk group, in which 6 of 6 patients recurred, and a low-risk group, in which 0 of 5 patients recurred (P = 0.004). Frequency of allelic loss in tumor suppressor genes may provide a useful adjunctive prognostic test in medullary thyroid carcinoma.