Adenoid Cystic Carcinoma of the Parotid Gland
Craniofacial pain symptoms are often complex in nature and can represent a variety of unrelated conditions. Just a few from a long list include cardiac ischemia and acute myocardial infarction,1 Ernest Syndrome and temporal tendonitis,2-5 temporomandibular joint pain, and salivary gland adenoid cystic carcinoma (ACC).6 These diverse conditions can have almost identical signs and symptoms. This case required the effort of seven different physicians and dentists in order for the patient to be diagnosed and receive effective treatment. He could have easily been misdiagnosed as a patient with atypical facial pain, TMJ, or atypical trigeminal neuralgia. His management would likely have relied on pain medications, and he would have missed his window of opportunity for timely intervention for parotid adenoid cystic carcinoma. Resection of the tumor eliminated the painful symptoms and radiation therapy may help to prevent reoccurrence. The literature indicates that ACC is less than 1% of all malignancies and less that 10% of all salivary gland neoplasms.7
For comparison, another serious example of craniofacial pain origin was reported by Kreiner and Okeson et al. at the University of Kentucky in a 2007 prospective multi-center study:1
“Of 186 patients with ischemic cardiac episode, 11 patients or 6 percent had craniofacial pain as the only complaint. Of those 11 patients three had acute myocardial infarction (AMI). The most common craniofacial pain locations included the throat, left mandible, right mandible, and left temporomandibular joint/ear region and the teeth.”
Another 60 patients in the study (32%) reported craniofacial pain along with pain in other regions.1 Kreiner and Okeson’s study concluded that craniofacial pain is commonly induced by cardiac ischemia. However, we know not all craniofacial pain represents cardiac ischemia. Some cases of craniofacial pain may be parotid gland masses as will be seen in this article.
Clearly, a complex pain patient who suffers craniofacial pain is fortunate to be diagnosed accurately. I say this because any one of about 10 diverse medical and dental disciplines—with no organized inter-relationships—may see such a complex craniofacial pain patient. The patient may—or may not—get definitive help depending on the condition(s) and the particular examiner’s scope of knowledge and ability. This article serves to underscore the fact that a routine patient may turn out to have a life-threatening condition such as adenoid cystic carcinoma (ACC). If not diagnosed, ACC could cost them their life. The at-risk patient may not exhibit any swelling, motor or sensory deficit, and may not have any signs that would raise the suspicion index to prompt a CT scan, MRI scan, or other test. If hurting, the patient may complain of craniofacial pain that seems routinely non-fatal such as ear pain, pain in jaw, or pain in teeth.
Adenoid Cystic Carcinoma
The outcome of a diagnosis of adenoid cystic carcinoma is somewhat different than that of other salivary and secretory gland tumors.8 Adenoid cystic carcinoma (ACC) is a considered a “rare” type of tumor. ACC is most commonly found within secretory glands of the head and neck, but other sites of origin include the trachea, lacrimal gland, breast, skin, and vulva.9 For a pathologist, this type of tumor is defined by its very distinctive microscopic appearance (see Figure 1). The differential diagnosis includes other benign and malignant neoplasms that appear in these locations. For example, ACC and polymorphous low-grade adenocarcinoma (PLGA) are two forms of salivary gland cancer that share many features. But, in other sites, ACC may be misidentified on histological grounds with basaloid squamous carcinoma (a squamous carcinoma variant).
Signs and Symptoms
Obviously signs and symptoms depend on size of the mass and the location of site of origin. Early lesions of ACC are usually painless masses involving the mouth or face, and most of the time are growing slowly. Advanced stage tumors of ACC are usually painful and may present with nerve pain or paralysis because ACC is known to favor peripheral nerves with perineural invasion. Tumors of the lacrimal gland may interfere with vision. Tumors arising in the larynx may lead to changes in speech while tumors of the parapharyngeal space may affect the parotid gland and associated neural, vascular, and dental structures.
Because of ACC’s slow and quiet growth, this malignant tumor often grows without the patient’s awareness until it affects other tissues with its insidious effect. The disease survival rate for ACC is approximately 89% at 5 years, but only about 40% at 15 years. Another unusual feature of the ACC tumor is that it seldom metastasizes to regional lymph nodes. Unfortunately the metastasis, when it does occur, shows up most often at distant sites such as the lung or the liver.10 Bone involvement usually indicates an increasingly aggressive clinical course. Features such as solid growth pattern, perineural invasion of sensory or motor nerves, or positive surgical margins of the excised specimen are considered to be indicators for a poor outcome.
Most patients are afflicted with this tumor in the fourth and fifth decades of life and it appears in females in a ratio of 3 to 2 over males. No strong genetic or environmental risk factors have been noted and, as with other tumors, damage to the DNA genome occurs early in the tumor’s development. Researchers believe there is evidence that the p53 tumor suppressor gene is de-activated in the more advanced or aggressive forms of the tumor.
Treatment at this point relies on excisional surgery to remove the tumor and histologic examination to determine variant type, as well as to determine if the margins are clear. Many medical centers rely on radiation therapy because of anecdotal evidence that radiation helps to limit failure. There are some institutions using neutron beam treatment with favorable results, and most treatment centers do not rely on the conventional chemotheraputic drugs because of a lack of effectiveness. Several clinical trials are examining new cancer drugs to determine effectiveness against the ACC tumor.