FINAL DIAGNOSIS:

Primary Adenoid Cystic Carcinoma of the Trachea

Discussion:

Adenoid cystic carcinoma (ACCa) of the trachea is a relatively uncommon lesion, however it is the second most common tracheal malignancy behind squamous cell carcinoma.^1,2  Together, these two entities account for greater than 2/3 of all primary tracheal neoplasms.^1,3   Interestingly enough, however, tracheal malignancies are exceptionally rare with an incidence of 0.2 per 100,000 persons per year.^1,3   The mean age for patients with ACCa of the trachea is 44 years, which is roughly 10 years younger than patients who develop squamous cell of the same location.^2,4   Men appear to be as equally affected as women.^1-4The majority of patients with ACCa of the trachea present with (in decreasing order of incidence) dyspnea, hemoptysis, cough, wheezing, dysphagia and stridor.⁴   While ACCa can occur anywhere in the trachea, most authors have found them to most often occur in the upper portion of the trachea. ²   This particular case is interesting for the fact that the lesion appeared to originate distally near the carina. ACCa is typically a slow-growing tumor that may present as a bulky, obstructive mass with poorly defined margins, however, compression of adjacent structures is more common than overt invasion.⁴  This is in contrast with SCCa, which will usually present as a large, exophytic mass with overt invasion. Metastases from ACCa can occur to peritracheal lymph nodes, however the lungs are the usual site.^1-3  Interestingly enough most patients who die of this disease do so as a result of obstruction from the primary lesion, rather than as a consequence of their lung mets.²

Most resected specimens consist of firm tumors that demonstrate poorly defined borders with a gritty tan-white cut surface. ²   Microscopically, ACCa of the trachea is identical to its counterparts elsewhere in the head and neck. The tumors are almost always composed of relatively uniform cells that demonstrate dark nuclei and scant cytoplasm. ^2,5  Typically, ACCa of the trachea will also demonstrate the classical growth patterns of cribriform, tubular and solid. This particular case exemplifies the cribriform appearance. The cribriform and tubular growth patterns can often aid in diagnosis, whereas the solid pattern can prove to be troublesome if only a small biopsy specimen is obtained. As with ACCa found elsewhere in the head and neck, those that occur in the trachea also show a propensity for traveling along nerves. Microscopic extension of these tumors has been documented up to 1cm beyond what was grossly visualized / palpated by the surgeon in many cases.¹   This exemplifies the need for intraoperative frozen sections to examine the surgical margins of resection. ¹

References

1. Maziak DE, Todd TR, Keshavjee SH, Winton TL, Van Nostrand P, Pearson FG. Adenoid cystic carcinoma of the airway: thirty-two-year experience. J Thorac Cardiovasc Surg 1996;112:1522-31; discussion 1531-2.
2. Heffner. Diseases of the Trachea. In: Barnes, ed. Surgical Pathology of the Head and Neck. New York: Marcel Dekker, 2001:620-621.
3. Azar T, Abdul-Karim FW, Tucker HM. Adenoid cystic carcinoma of the trachea. Laryngoscope 1998;108:1297-300.
4. Mathisen DJ. Tracheal tumors. Chest Surg Clin N Am 1996;6:875-98.
5. Allen MS. Malignant tracheal tumors. Mayo Clin Proc 1993;68:680-4.