Pulmonary adenocarcinoma: classification and molecular biology

Primary epithelial lung malignancies in the pediatric population

BACKGROUND

Primary epithelial lung malignancies are rare in childhood and adolescence. We reviewed the Memorial Sloan-Kettering Cancer Center experience with these tumors to better understand their histology, time to diagnosis, treatment, and outcome.

PROCEDURE

A retrospective review was performed on all patients 21 years of age or younger at diagnosis, treated for primary epithelial lung malignancies at Memorial Sloan-Kettering Cancer Center between 1980 and 2001.

RESULTS

We identified 11 patients with primary epithelial lung malignancy. The median age at diagnosis was 19 (range: 12-21) years. The most common radiographic abnormality was a mass (55%) on chest imaging. Seven patients (64%) were initially diagnosed as having pneumonia which contributed to a delay in diagnosis. Final pathologic diagnoses included adenocarcinoma (four), carcinoid tumor (three typical, one atypical), basaloid carcinoma (two), and mucoepidermoid carcinoma (one). A majority of patients presented with advanced disease (two stage III, four stage IV). Patients with localized disease were treated with surgical resection and all but one remains disease free with a median follow-up of 60 months (range: 13-286). Patients with either advanced locoregional or distant metastatic disease were treated with multimodal therapy and a majority had rapid progression of disease.

CONCLUSIONS

When children and adolescents present with primary epithelial lung malignancy a majority will have advanced disease and experience a delay in diagnosis. The histologic types of tumors encountered are similar to lung tumors occurring in adults, although the frequency of the various types differs. Carcinoid tumors are more frequent, and less common subtypes of bronchogenic carcinoma are also more prevalent in the pediatric age group. Similar to the adult population, the prognosis of these tumors is dependent on histology and stage. Patients with carcinoid tumors seem to have the best prognosis, followed by adenocarcinoma. The highly aggressive basaloid carcinoma has the worst.

Heterogeneous distribution of P53 immunoreactivity in human lung adenocarcinoma correlates with MDM2 protein expression, rather than with P53 gene mutation

Although the tumor suppressor p53 protein (P53) immunoreactivity and its gene (p53) mutation were reported to be significant prognostic indicators for human lung adenocarcinomas, little is known regarding the relationship between the heterogeneous distribution of P53 and its genetic status in each tumor focus and the clinicopathological significance. To determine how P53 is heterogeneously stabilized in patients, we compared P53 expression to both the p53 allelic mutation in exon 2 approximately 9 by polymerase chain reaction-single strand conformation polymorphism using microdissected DNA fractions, and the immunohistochemical MDM2 expression. Of the 48 positive to P53 in 118 lung adenocarcinomas examined, 10 with heterogeneous P53 expression were closely examined. The higher P53 expression foci in 7 of 10 cases were less differentiated, histologically in respective cases, and were frequently associated with fibrous stroma. Two had genetic mutations in exon 7 of the p53 gene in both the high and low P53 expression foci of cancer tissue indicating no apparent correlation between heterogeneous P53 expression and the occurrence of gene mutation. Immunohistochemical expression of MDM2 was significantly lower in high P53 expression areas (p < 0.05, the mean labeling indices of high and low P53 expression areas being 4.2 +/- 5.4% and 13.6 +/- 12.2%, respectively). In addition, among all the 118 cases examined, MDM2 expression was significantly suppressed in cases of p53 gene mutation, simultaneously with P53 overexpression, as compared with cases without both the p53 mutation and expression (p < 0.001). These findings suggest that the heterogeneous stabilization of P53 in human lung adenocarcinomas could be partly due to suppressed MDM2 expression. The overexpression of non-mutated P53 may afford a protective mechanism in human lung adenocarcinomas.