Immunohistochemical expression of estrogen and progesterone receptors in primary pulmonary neuroendocrine tumors.

CONTEXT Lung and breast carcinomas are among the most prevalent cancers. Advances in cancer therapies can provide survival benefit and be potentially curative, even in metastatic disease. Due to the high prevalence of these carcinomas, it is not unusual to encounter lung nodule(s) in a patient with breast carcinoma, and distinguishing between primary and metastatic disease is critical for management/treatment. Occasionally neuroendocrine differentiation is present in breast carcinoma, making its distinction from pulmonary/nonpulmonary neuroendocrine tumors in the lung difficult. OBJECTIVE To assess estrogen and progesterone receptor expression in the entire spectrum of pulmonary neuroendocrine tumors. DESIGN Seventy-one neuroendocrine neoplasms including typical carcinoids (42), atypical carcinoids (7), small cell carcinomas (14), large cell neuroendocrine carcinomas (2), and combined small cell carcinomas (6) were evaluated for estrogen and progesterone receptors. Mammary and non-small cell lung carcinomas were also stained for comparison. RESULTS The entire spectrum of neuroendocrine neoplasms demonstrated focal to diffuse estrogen (typical carcinoid, 23; atypical carcinoid, 6; small cell carcinoma, 8; large cell neuroendocrine carcinoma, 2; combined small cell carcinoma, 4) and progesterone (typical carcinoid, 11; atypical carcinoid, 2; small cell carcinoma, 7; large cell neuroendocrine carcinoma, 0; combined small cell carcinoma, 2) expression. There was no correlation between sex and estrogen/progesterone status. Estrogen and progesterone staining were also noted in endothelial cells. Relative to neuroendocrine carcinomas, mammary carcinomas expressed estrogen and progesterone more frequently. Non-small cell carcinomas had greater and similar immunoreactivity for estrogen and progesterone, respectively. CONCLUSIONS Although estrogen and progesterone receptor staining is frequently associated with breast and gynecologic primaries, it can also be observed in "nontarget" organs. Therefore, presence of estrogen and/or progesterone expression in neuroendocrine tumors involving the lung should not exclude a primary pulmonary neoplasm.