Adenoid Cystic Carcinoma of Trachea: Findings on ¹⁸F FDG Positron Emission Tomography-Computed Tomography

A 51-year old woman presented with chief complaints of nonproductive cough with dyspnea for the past 6 months to pulmonology outpatient department. On suspicion of bronchogenic carcinoma, ¹⁸F FDG positron emission tomography-computed tomography (PET-CT) was advised to look for sites of metabolically active disease. Maximum intensity projection images of the scan showed focal area of FDG uptake in the mediastinal region [Figure 1a, solid blue arrow]. Figure 1b [solid white arrow] represents the axial chest CT image showing an extraluminal lesion measuring approximately 1.4 cm × 1.4 cm arising from the trachea just before its bifurcation and also involving the carina. The lesion showed increased FDG uptake in the fused transaxial PET-CT images [Figure 1c, solid red arrow]. Figure 1d [solid yellow arrow] and e [solid green arrow] represents coronal and sagittal fused ¹⁸F FDG PET-CT images respectively, showing increased FDG uptake in the tracheal lesion. No distant metastasis was recorded on PET-CT scan and the patient underwent surgery and histopathology was diagnostic of primary adenoid cystic carcinoma (ACC) of the trachea.

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Figure 1 (a) Maximum intensity projection images of the ¹⁸F FDG positron emission tomography-computed tomography scan showing focal area of FDG uptake in the mediastinal region (solid blue arrow). (b) Axial chest computed tomographic image showing a lesion 1.4 cm × 1.4 cm arising from trachea (solid white arrow). (c) Tracheal lesion show increased FDG uptake in the fused transaxial positron emission tomography-computed tomography images (solid red arrow). (d) Fused coronal ¹⁸F FDG positron emission tomography-computed tomography image showing increased FDG uptake in the tracheal lesion (solid yellow arrow). (e) Fused sagittal ¹⁸F FDG positron emission tomography-computed tomography image showing increased FDG uptake intratracheal lesion (solid green arrow)

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Tracheal ACC originates from the submucosal glands of the airway are often misdiagnosed as asthma or bronchitis and accounts for about 10%–20% of the malignant tracheal tumor.[12] Due to rarity of this neoplasm in general population, there are not many published reports highlighting the utility of PET-CT in this type of tumor. Although some reports suggest that there is no special tumor site predilection,[3] Huo et al. in their series found lower one third of trachea to be one of the favored sites.[4] Metastases to cervical lymph nodes are a rare event; ACC spreads through a hematogenous route with distant metastases, especially to lungs, brain, bone and liver.[56] In our case, we had a localized disease with no nodal or visceral metastases; however, keeping in view its tendency to metastasize initially as well as late up to 15 years after the initial diagnosis,[7] the authors advocate use of ¹⁸F FDG PET-CT in workup algorithm of ACCs, especially for restaging purpose.