chest radiology

CHEST RADIOLOGY

Case 16:

A 60-year-old female presents with repeated attacks of respiratory tract infection. CT scan of the chest is performed.
What is the diagnosis?


Fig 1	Fig 2(contrast)

Fig 3(contrast)	Fig 4

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Imaging Findings
Collapse of the left upper lobe is noted, with a minimally enhancing endobronchial mass lesion.

Diagnosis

Lung carcinoid

Discussion

Bronchial carcinoid tumors are rare, accounting for as many as 2.5% of all pulmonary neoplasms and for 12-15% of carcinoid tumors overall. They originate from the neurosecretory cells of bronchial mucosa and were previously classified as bronchial adenomas, a term no longer used. Bronchial carcinoids are now classed as low-grade malignant neoplasms because of their potential to cause local invasion, their tendency for local recurrence, and their occasional metastases to extrathoracic sites. Bronchial carcinoid tumors arise from Kulchitsky cells (argentaffin cells) within the bronchial mucosa. The predominant distribution of cells occurs at the bifurcation of the lobar bronchi.

Histologically, bronchial carcinoids can be categorized into two groups: Kulchitsky cell carcinoma (KCC) I (typical carcinoids), KCC II, (atypical carcinoids).
KCC I is the classic or typical bronchial carcinoid and the least aggressive. These tumors are usually well defined, smaller than 2.5 cm in diameter, centrally placed within the mainstem bronchi, and associated with endobronchial growth.
KCC II tumors are atypical carcinoids and account for one quarter of lung carcinoid tumors. These lesions are much more aggressive than typical carcinoids. They usually affect relatively old patients with a male preponderance, they are larger than the others at presentation, and they tend to occupy a peripheral location.

Most tumors follow a benign course and are amenable to surgery. The 5-year survival rate for patients with typical bronchial carcinoid (KCC I) is 94%.

CT provides excellent anatomic detail of both the endobronchial and the extraluminal components of the tumor. Tumors usually deform or obstruct the adjacent bronchus, and even peripheral tumors are shown to lie in immediate proximity to a recognizable small airway. As on CXRs, lesions usually appear as well-defined, lobulated, round or oval masses sized 2-4 cm. Extension into adjacent mediastinal structures is detectable on CT scans in more aggressive tumors.
Lesions are highly vascular and usually demonstrate marked homogeneous enhancement on CT scans obtained after the intravenous administration of contrast material. However, some carcinoid tumors (particularly atypical carcinoids) may show heterogeneous or no enhancement. Limitations regarding the specificity apply to CT as with Chest X-ray, and bronchoscopic or percutaneous image-guided biopsy may be necessary for definitive diagnosis.