Material and Method: Over a period of one year, computerized tomography (CT)–guided FNAC was performed in forty patients presenting with respiratory symptoms with a localized lung lesion clinically, which was confirmed radiologically.

Results: Male preponderance was noted in this study with M:F ratio of 2.08:1. Malignancy was the predominant lesion found in this study with twenty-four cases (60%). Among the malignant lesions, adenocarcinoma was the commonest malignancy followed by squamous cell carcinoma. Material in two cases was inadequate for interpretation. Adenocarcinoma was the commonest malignancy seen in females. However, adenocarcinoma was still more common in males overall. Squamous cell carcinoma was the commonest malignancy seen in males. Squamous cell carcinoma was the commonest malignancy among smokers. The diagnostic accuracy was 95% considering cytological criteria as the standard.

Conclusion: Transthoracic CT-guided FNAC is a relatively safe and accurate procedure in the diagnosis of difficult lung lesions. FNAC should be used earlier and more frequently to shorten the diagnostic interval and allow more prompt therapy for persistent lung lesions.

The results were classified into five categories: (1) Inflammatory, (2) Granulomatous lesion/ Tuberculosis, (3) Suspicious of malignancy, (4) Positive for malignancy, (5) Inadequate for interpretation

Table I shows the distribution of the cases. The predominant lesion found in this study was malignancy in twenty-four cases (60%), followed by an inflammatory lesion in twelve cases (30%). One case each was reported as suspicious of malignancy (2.5%) and as a granulomatous lesion (2.5%) (Figure 1). The material was inadequate for interpretation in two cases (5%). Out of twenty-four FNAC-proven cases of malignancy, twenty were males (83.33%) and only four were females (16.66%). Hence, there was a significant male preponderance in malignant cases with a M:F ratio of 5:1. Table II shows the cytological typing of malignant lesions. The most common malignant lesion seen was adenocarcinoma in twelve cases (30%) (Figure 2). Two of these were diagnosed as bronchioloalveolar carcinoma (Figures 3,4). Squamous cell carcinoma was diagnosed in nine cases (22.5%) whereas three cases were classified as undifferentiated carcinomas (7.5%) (Figures 5,6,7).

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Figure 1: Granulomatous lesion – A cluster of epitheloid cells and few lymphocytes (MGG, x400).

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Figure 2: Adenocarcinoma – Neoplastic cells with delicate cytoplasm and pleomorphic, hyperchromatic nucleus arranged in cell clusters and glandular pattern (arrow) (Pap, x400).

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Figure 3: Bronchioloalveolar carcinoma – Mildly pleomorphic cells arranged in cohesive sheets (Pap, x100).

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Figure 4: High power of the above tumor showing prominent intranuclear vacuoles (Pap, x400).

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Figure 5: Squamous cell carcinoma – A cluster of neoplastic squamous cells with highly pleomorphic cells having ample eosinophilic cytoplasm (Pap, x400).

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Figure 6: Undifferentiated carcinoma – Highly pleomorphic, undifferentiated cells in sheets (MGG, x400).

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Figure 7: Undifferentiated carcinoma – Highly pleomorphic, undifferentiated cells in sheets (Pap, x400).

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Table I: Distribution of cases

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Table II: Cytological typing of malignant lesions

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Table III: Association with smoking

Adenocarcinoma was the commonest malignancy seen in females. Three out of four females positive for malignancy were diagnosed as adenocarcinoma. However, adenocarcinoma was still more common in males overall with a M:F ratio of 2.3:1. Squamous cell carcinoma was the commonest malignancy seen in males with a M:F ratio of 3.5:1.

Table II shows the association with smoking. Sixteen out of forty patients were smokers. All of them were males. Thirteen out of sixteen smokers were positive for malignancy (81.25%). Squamous cell carcinoma was diagnosed in seven of these thirteen patients and five were diagnosed as adenocarcinoma, of which one was diagnosed as bronchioloalveolar carcinoma. There was therefore a strong predisposition to develop lung carcinoma among smokers and squamous cell carcinoma was the commonest malignancy among smokers. No major complications were encountered in this study, however one patient developed dyspnoea following FNAC. He was treated successfully with an adrenaline injection (Figure 1-7).

Different imaging modalities such as fluoroscopy, ultrasonography, and computed tomography have been used by various authors^{1,4,7,13,16-18}. Computed tomography is widely used nowadays^16,17,19,20.

The present study consisted of forty-three aspirations performed on forty patients. In three cases (7.5%), repeat aspiration helped to obtain adequate material as the material was inadequate in the first instance. The aspiration was repeated in these cases as there was a strong suspicion of malignancy on clinical and radiological examination. Different studies cite a repeat aspiration rate of 13% for an inconclusive first aspiration. It is also stated that an unsatisfactory aspiration must be repeated, particularly when there is strong suspicion of possible malignancy¹³.

In two cases (5%), the material was inadequate for interpretation but aspiration could not be repeated either because the patient was uncooperative or lost to follow up. Various studies have shown the rate of inadequate sampling to vary from 8.8% to 25.4%^1-3,6,7. The reasons quoted are faulty technique, necrosis, tumor location and patient compliance⁴.

There was a male preponderance in the present study with a M:F ratio of 2.08:1. The ratio in lung lesions as quoted by various authors ranges from 1.7:1 to 2.6:1. This difference is explained on the basis of higher incidence of predisposing factors like smoking, COPD and alcoholism in males^21,22. Among FNAC-proven cases of malignancy, twenty were males (83.33%) and only four were females (16.66%). There was therefore a significant male preponderance with a M:F ratio of 5:1.

Twenty-four cases were positive for malignancy (60%) in the present study. The features were suspicious of malignancy but FNAC could not be repeated as the patient was lost for follow up in one case (2.5%). Repeated aspirations helped to obtain a specific diagnosis later in three cases. Various studies cite the incidence of malignant tumors on lung FNAC as 58-88%. The above findings correlated with the observations made by various authors^9,21,23,24.

Adenocarcinoma was the commonest tumor in females. Three of four females were diagnosed as adenocarcinoma. However it was still more common in males overall with a M:F ratio of 2.3:1. Squamous cell carcinoma was the commonest tumor in males with a M:F ratio of 3.5:1.

Cancer of the lung is a disease of middle and late periods. The incidence is low in those below 35 years, rises to a peak at about 60 years and declines slowly thereafter. In the present study, sixteen patients were smokers (40%) and all of them were males. Thirteen of 16 were positive for malignancy (81.25%). Among the smokers, squamous cell carcinoma was the commonest malignancy with seven cases (53.8%) followed by adenocarcinoma with 5 five cases (38.46%). These findings correlated with the results of previous authors. The relationship with smoking is strongest for squamous cell carcinoma^21,22.

Twelve of our cases were diagnosed as adenocarcinoma (30%) that included two cases of bronchioloalveolar carcinoma closely followed by squamous cell carcinoma in nine cases (22.5%). Though squamous cell carcinoma used to be considered the commonest tumor of the lung, studies indicate that adenocarcinoma may have overtaken it in incidence^21,22.

Bronchioloalveolar carcinoma constituted two cases in the present study (5%). One of these patients was a smoker. BAC represents 1-9% of all lung cancers in various series. It is less frequently associated with a history of smoking than are squamous cell carcinomas. More than 75% of these are still found in smokers²².

Between 20-30% of lung carcinomas are adenocarcinomas and the proportion has risen in the last fifteen years. Adenocarcinoma is the most common histological type in women and the rising proportion of women in the lung cancer population is undoubtedly a factor in the relative increase in the incidence of adenocarcinoma^9,21.

Three cases were diagnosed as undifferentiated carcinoma in the present study (7.5%). Undifferentiated carcinoma constitutes 7-15% of lung cancers. As no immunocytochemical studies were done in the present study, the above three cases were diagnosed as undifferentiated carcinoma and no further typing could be done²¹. Complications were encountered in only one case (2.5%), which developed dyspnoea following FNAC. No fatalities were reported in the present study. However major complications have been reported by previous workers, the commonest complication being pneumothorax^{5,6,9,10,18,23,24}.

Other carcinomas of the lung i.e. small cell carcinoma, giant cell carcinoma and adenosquamous carcinoma were not found in this study. The possible explanation can be the relative rarity of these neoplasms. Small cell carcinoma accounts for 10 – 20% whereas both giant cell carcinoma and adenosquamous carcinoma make up less than 5% of lung malignancies. The site of occurrence of small cell carcinoma is further a hindrance to its diagnosis by FNAC. It occurs predominantly in the central portions of the lung, in the major bronchi^21,22.

It is an accurate, safe and repeatable procedure in the diagnosis of difficult lung lesions. CT scan has enabled the visualization of previously inaccessible tumors, which can now be guided by this procedure, leading to a greater yield of cytological material and a significantly greater predictability of true positive cases in malignant lesions. FNAC should be used earlier and more frequently to shorten the diagnostic interval and allow more prompt therapy for persistent lung lesions.

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