COM August 2013 Diagnosis

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A firm, long-standing nodule of the upper lip should make a clinician think of canalicular adenoma since the upper lip is the most common location for that neoplasm. The age of the patient is consistent with that of most patients who present with canalicular adenoma, but not the gender. Nonetheless, canalicular adenoma should be on the differential diagnosis. The histology is not supportive of canalicular adenoma.

Canalicular adenoma is a benign neoplasm that is almost exclusively of minor salivary gland origin. The upper lip is the most common location, accounting for over 80% of all cases, followed by the buccal mucosa. Occurrences in the parotid gland and other major salivary glands are described, but rarely. They present as well-circumscribed, firm, movable, slow-growing, painless nodules. They occur in females over the age of 50 and are usually single nodules. However, canalicular adenomas are sometimes known to present in a multifocal manner, which a clinician may mistake for invasion or metastasis. They are treated by simple enucleation. Histologically, canalicular adenomas present as an encapsulated neoplasm with cords, duct-like structures of monotonous, cuboidal or low columnar basaloid cells, and sometimes with large cystic dilatation of the duct-like spaces.

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A firm, long-standing nodule on the upper lip should also make a clinician think of the most common benign neoplasm of the salivary gland origin, which is pleomorphic adenoma (PA). The age and gender of this patient are not typical of PA, but this condition should nonetheless be included on the differential diagnosis of a swelling of the upper lip. The histology in this case, however, was not supportive of PA.

Pleomorphic adenoma is the most common benign salivary gland neoplasm of both the major and minor salivary glands. It originates from the myoepithelial cells and the reserve cells of the intercalated ducts. It accounts for 80% of all benign salivary gland neoplasms. It occurs in both major and minor salivary glands and accounts for up to 77% of parotid, 68% of submandibular, and 43% of minor salivary gland tumors. It is most common in females 30-50 years of age, but it is also described in children. One study reports 1% of cases affecting children under 10 years of age and 5.9% of cases occurring in patients between the ages of 10 and 20. PA presents as a small, painless, slowly enlarging nodule. If left untreated, it can enlarge significantly, sometimes increasing by several pounds in weight. It occurs in the oral cavity, especially the palate and lips. On the palate, it is usually located in the posterior hard palate or anterior soft palate but can also be in the posterior soft palate; PA usually occurs in the posterior and lateral palate, as opposed to torus palatines, which usually occurs in the middle hard palate and in the anterior. The posterior hard palate mixed tumor is fixed due to the bone-bound anatomy of the region; the tumor is otherwise movable. Histologically, mixed tumor has a wide variety of cellular and pattern manifestations. The main cellular components are epithelial duct-like structures and mesenchymal-like tissue such as myxochondroid matrix. These lesions are generally encapsulated, ranging from predominantly myxoid (36%) to extremely cellular (12%). Complete surgical removal with clean margins is the preferred treatment. Palatal lesions respond well to excision in one piece with the periosteum and overlying mucosa. Pleomorphic adenoma has a good prognosis, but it has a tendency for recurrence (up to 44%) if not treated thoroughly. The risk of recurrence is less if it occurs in the minor salivary glands (up to 20%). The risk of malignant transformation is about 5%.

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Soft tissue neoplasms can be long-standing and do occur on the upper lip. For that reason, they should be considered on the differential diagnosis. Schwannoma should be considered for a firm nodule of the upper lip since this location is a relatively common location for this neoplasm. The age of this patient is not typical and is on the older end of the age range in which this condition occurs. The histology is not supportive of schwannoma.

Schwannoma is a benign, firm, smooth-surfaced, encapsulated and mobile neoplasm of Schwann cell origin. It occurs at any age but is more common in individuals 30-50 years of age with equal sex distribution. The tongue is the most common location, followed by the floor of mouth and the lips. It is also described as occurring within the jaw bones, especially the mandible. Up to 48% of schwannomas occur in the head-and-neck area. They are usually isolated lesions unless they present as part of neurofibromatosis type 1. Shwannoma presents as a slow-growing, firm, rubbery, smooth-surfaced nodule. The histology is usually diagnostic where the lesion is encapsulated and has two patterns: antoni A, the cross section of which gives rise to “verocay bodies,” and antoni B, which is loose and resembles neurofibroma. Simple excision is the treatment of choice and recurrence is rare.

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The history of twenty-year long standing nodule argues strongly against a metastatic disease. Nonetheless this is a metastatic renal cell carcinoma. It is hard to speculate as to what was present in that area for twenty years. The histology did not show anything beside the metastatic nodule.

Cancer metastasis to the oral cavity is neither specific nor common. Although such cases constitute less than 1% of all oral malignant neoplasms, it may have a devastating result to the patient mainly because metastasis to other sites has already developed or is inevitable. Theoretically, any malignant neoplasm can metastasize to the oral cavity, but in actuality few do and of the ones that do, the majority are carcinomas rather than sarcomas. The most common malignant neoplasms that metastasize to the mouth are from the breast, lung, kidney, prostate and colon. Malignant neoplasms from the pancreas, esophagus, thyroid, cervix, and liver have also been described. Breast cancer is the most common neoplasm to metastasize to the oral cavity altogether. Lung and prostate cancers are the most common neoplasms to metastasize to the oral cavity in men. In most cases, the oral presentation is a secondary diagnosis when the primary diagnosis of malignancy in a distant organ has been already made and the patient has had or is undergoing treatment for it. In rare cases, the oral lesion is the first manifestation of the disease. By far the most common location is the posterior mandible, where 80% of cases occur, followed by the gingiva. This condition is mostly described in adults over the age of 30 and rarely in children. Pain and swelling are the most common clinical symptoms. Metastatic lesions may also present as asymptomatic, simulating a periapical lesion, or with gingival swelling like a pyogenic granuloma. They can cause anesthesia and parasthesia, especially when they involve the inferior alveolar canal. The latter results in so-called “numb-chin syndrome.” Tooth loosening, displacement and sharp resorption have also been described. The radiographic appearance of the borders can range from moderately well demarcated to diffusely irregular. The majority of neoplasms cause bony destruction with ill-defined borders; the moth-eaten appearance of some bony destruction indicates aggressive behavior. It is also important to mention that at times, well-demarcated lesions with a benign morphology, as well as cystic radiographic morphology, have also been described. Metastatic neoplasms from the prostate and, rarely, from the breast can be bone-forming, resulting in radiopaque or mixed radiolucent and radiopaque lesions misdiagnosed as benign fibro-osseous lesions. Tumor metastasis to the oral cavity carries a poor prognosis because the oral cavity is usually not an isolated site and tends to project a more disseminated clinical behavior. Patients are typically treated with chemotherapy and the five-year survival rate is poor.