The Five Basic Techniques of Lung Cytology

PHILADELPHIA—The growing use of pulmonary cytology, and consequent increasing experience of cytopath-ologists, has raised the diagnostic accuracy of the five basic pulmonary cytology techniques, Nadia Al-Kaisi, MD, told Oncology News International in an interview after her workshop on the subject at the annual fall meeting of the American Society of Clinical Pathologists (ASCP) and College of American Pathologists (CAP).

Dr. Al-Kaisi, associate professor of pathology, Case Western Reserve University, said that the five basic techniques of pulmonary cytology involve sputum, bronchial brushings, bronchial aspirates and washings, bronchoalveolar lavage, and fine needle aspiration (FNA).

She noted that in addition to its use in cancer diagnosis, pulmonary cytology is also increasingly being used to diagnose the opportunistic infections seen in immunocompromised patients. Thin-Prep instruments, she added, are also increasingly being used to prepare pulmonary cytology smears.

Another new approach in this area is the use of immunoperoxidase techniques in the differential diagnosis of primary vs metastatic lung malignancies. “Immuno-peroxidase technique is an immunohistochemical stain that utilizes antibodies specific to certain tumor markers,” she said, adding that “the specificity of these tumor markers varies.”

She said that FNA is becoming increasingly popular in the diagnosis of lung masses out of the reach of the broncho-scope. This is the result, she said, “of the availability of sophisticated radiologic imaging techniques.”

Percutaneous transthoracic FNA of the lung is performed under CT or fluoroscopic guidance. “Direct smears are made and stained either with Papan-icolaou stain or with a quick H&E [hematoxylin and eosin] stain in cases where determination of adequacy of the smear needs to be evaluated,” she said.

Transbronchial FNA, performed through a bronchoscope, has been used recently to diagnose lung lesions that have not ulcerated the bronchial mucosa, she said. In this approach, the processing of the cellular material is similar to that used with percutaneous FNA.

Cigarette smoking, she said, is the “most frequent toxin associated with squamous cell metaplasia, and habitual marijuana smoking may produce similar changes in the bronchial epithelium as those observed with cigarette smoking.”

These changes, she said, include the presence of atypical/dysplastic cells, reactive columnar cells, eosinophils, and “purse” cells. The later are observed in sputum and represent flat squamous cells with a large cytoplasmic vacuole taking up the majority of the cells. The large vacuole usually contains numerous neutrophils.

Metastatic cancer to the lung is more common than primary lung cancer, Dr. Al-Kaisi said, noting that 30% to 53% of patients who die from malignancy have pulmonary metastases.

However, she added, many metastatic lung cancers do not shed cells into sputum or bronchial material because the overlying bronchial mucosa is not ulcerated.

Leukemic infiltrates in the lung occur in as many as 90% of leukemic patients, she said. “Any subtype can be seen, but chronic lymphocytic leukemia is the most common type encountered.”

She advised cytopathologists that familiarity with the less frequent primary lung neoplasms can prevent misdiagnosis. These include adenoid cystic carcinoma, mucoepidermoid tumor, pleomorphic adenoma of bronchi, pulmonary blastoma, fibrous mesothelioma, Schwannoma, and smooth muscle tumors.