Adenoid cystic carcinoma in trachea : A rare presentation

Email: pandeygreta@hotmail.com Primary tracheal tumors are rare. Adenoid cystic carcinoma of trachea is even rarer. It occurs as a polypoidal mass in trachea presenting with dyspnea and respiratory distress due to tracheobronchial obstruction. We report a case of young male presenting with dyspnea for some time. CT scan revealed mass in trachea obliterating its lumen. Histopathological examination conirmed the diagnosis. ABSTRACT


INTRODUCTION
Adenoid cystic carcinoma is a rare tumor of salivary gland origin, found mostly in head and neck region but has also been reported in breast, lacrimal gland of eye, lung, bartholin's gland, trachea and parasanal sinuses. 1,2Primary tracheal tumors are rare and constitute only two 2% of all respiratory tract tumors. 1 Adenoid cystic carcinoma is the second most common malignant tracheal tumor after squamous cell carcinoma. 1,2These tumors should be considered because they often present as dyspnea or respiratory distress and Pandey G 1 , Thakur B 2 , Devkota M  hence misdiagnosed and treated as asthma for months to years or sometimes until even with metastasis. 3We report a case of young male presenting with polypoidal tracheal mass with complains of dyspnea and respiratory distress as initial clinical presentation.Histopathological examination revealed it as Adenoid cystic carcinoma, a malignant tumor of salivary gland origin.

CASE REPORT
A 31 year-old male presented with respiratory distress for 3 months.All the base line blood investigations were within normal limits.Bronchoscopy showed an intramucosal 2x2cm mass at mid trachea approximately 5 cm distal to vocal cord and 6 cm proximal to carina.CT scan revealed well deined heterogeneously enhancing broad based polypoidal soft tissue mass of 20x19x14.5mm from posterior wall of trachea obliterating its lumen.(ig.1)Bilateral lungs have normal aeration.Operative indings revealed polypoidal mass measuring 2x2 cm attached to trachea over mid trachea with intact adventitia.Mass was obliterating around 80%of tracheal lumen.(ig.2)No palpable lymph nodes present.
Grossly, tracheal tissue with an intraluminal mass attached to tracheal ring.Microscopically lesion revealed basaloid cells arranged in iniltrating cords, cribriform pattern along with some tubules.(ig.3)Tumor cells show moderate degree of atypia.Some pseudocyst with eosinophilic secretions noted.

DISCUSSION
Adenoid cystic carcinoma of trachea was irst described clinically and pathologically by Billroth in 1859.These are rare malignant tracheal tumors occurring in only 0.2 per 100000 people per year accounting for under 0.1% of the cancer deaths per year.2][3] Primarily these arise from the minor salivary glands and sero-mucinous glands of upper respiratory tract.Tracheal tumors are present mostly in lower and upper third with a tendency to originate at lateral and posterolateral wall near the junction of cartilaginous and membranous portions. 1,2Squamous cell carcinoma is the most common pathology in smokers while adenoid cystic carcinoma is more prevalent among non-smokers.4Benign tumors are xanthogranulomas and pleomorphic adenoma. 3,4ese tumors show equal sex distribution and tend to occur in the fourth and ifth decades of life. 5Clinically they present with respiratory symptoms such as coughing, wheezing and dyspnea, hemoptysis, recurrent pneumonitis and are often treated for asthma for many time before they are correctly diagnosed. 1,3In our case they presented dyspnea followed by respiratory distress for 3 months.
The radiological appearance of tumors can be classiied as: intra-luminal, wall thickening, exophytic form.Endoscopic evaluation reveals that the majority of lesions are bulky and obstructive.The main advantage of imaging is demonstration of tracheal wall thickening and extraluminal changes. 4CT scan is useful and highly accurate in assessment of tumor location, invasion and metastasis. 1 Pathologically they present as smooth polypoidal mass obliterating the airway lumen of trachea.They occasionally grow circumferentially or in annular pattern.They can spread along both submucosal and perineural planes which are responsible for local late recurrences. 1,2They mostly have indolent behavior with a prolonged slow and insidious progression, in several years, despite its chances of local recurrences and distant metastasis. 2 However when it is associated with distant metastasis, survival is frequently less than 2 years. 3,6Metastasis to brain, liver, kidney, skin, abdomen and heart have been reported. 7enoid cystic Carcinoma often invaded the cartilaginous plate of trachea, extending to lung parenchyma and even to hilar and mediastinal soft tissue.They show heterogenous growth patterns, where the neoplastic cells are arranged in cribriform pattern, tubules and solid nests.These tumour cells are small with scant cytoplasm and dark hyperchromatic oval to angulated nuclei.Mitotic igures are not frequent.Formation of pseudocyst illed with eosinophilic Periodic Acid Schiff positive material or basophilic granular material are noted.Perineural invasion is often noted.The cells of origin include intercalated ducts, myoepithelial cells, secretory cells, and pluripotent reserve cells.Immunohistochemistry markers and staining pattern vary depending upon tumour histogenesis.They express cytokeratin, vimentin, smooth muscle actin, p63, and GFAP.The surrounding matrix recapitulates a basement membrane like material staining with type IV collagen, laminin, heparin sulphate. 5,8,9commended treatment consists of surgical resection with postoperative radiotherapy.However they have signiicant local invasion at the time of detection, making surgical resections more extensive. 3Our patient is doing well and is   on regular follow-up. 10

CONCLUSION
Tracheal adenoid cystic carcinoma presenting with respiratory distress may be misleading and hence correct diagnosis may be delayed.The publication of this article is to make aware about the unusual presentation of adenoid cystic carcinoma in trachea, which is slow growing, has multiple recurrences with late metastasis.Prompt diagnosis and treatment with regular follow up is needed.

Figure 1 :
Figure 1: CT scan showing mass in tracheal lumen.Figure 2: Photograph of trachea with polypoidal mass obliterating the lumen.

Figure 2 :
Figure 1: CT scan showing mass in tracheal lumen.Figure 2: Photograph of trachea with polypoidal mass obliterating the lumen.