Warthin Tumor (Salivay Gland Neoplasm) - part 2

Warthin Tumor (Salivay Gland Neoplasm) - part 2
Warthin tumor or papillary cystadenoma lymphomatosum is a benign neoplasm that occurs almost exclusively in the parotid gland. Although it is much less common than the pleomorphic adenoma, it represents the second most common benign parotid tumor, accounting for 5% to 14% of all parotid neo- plasms. The name adenolymphoma also has been used for this tumor, but this term should be avoided because it overemphasizes the lymphoid component and may give the mistaken impression that the lesion is a type of lymphoma. Analyses of the epithelial and lymphoid components of the Warthin tumor have shown both to be polyclonal; this suggests that this lesion may not represent a true neoplasm but would be better classified as a tumorlike process.
The pathogenesis of these tumors is uncertain. The traditional hypothesis suggests that they arise from heterotopic salivary gland tissue found within parotid lymph nodes. However, researchers have also sug- gested that these tumors may develop from a prolifera-tion of salivary gland ductal epithelium that is associated with secondary formation of lymphoid tissue. This latter theory is supported by studies that have found cytogenetic abnormalities in the epithelial component. A number of studies have demonstrated a strong asso- ciation between the development of this tumor and smoking. Smokers have an eightfold greater risk for Warthin tumor than do nonsmokers.
The Warthin tumor usually appears as a slowly growing, painless, nodular mass of the parotid gland. It may be firm or fluctuant to palpation. The tumor most frequently occurs in the tail of the parotid near the angle of the mandible, and it may be noted for many months before the patient seeks a diagnosis. One unique feature is the tendency of Warthin tumor to occur bilaterally, which has been noted in 5% to 17% of reported cases. Most of these bilateral tumors do not occur simultaneously but are metachronous (occurring at different times).
In rare instances, the Warthin tumor has been reported within the submandibular gland or minor salivary glands. However, because the lymphoid com- ponent is often less pronounced in these extraparotid sites, the pathologist should exercise caution to avoid
overdiagnosis of a lesion better classified as a papillary cystadenoma or a salivary duct cyst with oncocytic ductal metaplasia.
Warthin tumor most often occurs in older adults, with a peak prevalence in the sixth and seventh decades of life. The observed frequency of this tumor is much lower in blacks than in whites. Most studies show a decided male predilection, with some early studies demonstrating a male-to-female ratio up to 10:1. However, more recent investigations show a more bal- anced sex ratio. Because Warthin tumors have been associated with cigarette smoking, this changing sex ratio may be a reflection of the increased prevalence of smoking in women over the past few decades. This association with smoking also may help explain the frequent bilaterality of the tumor, because any tumori- genic effects of smoking might be manifested in both parotids.
The Warthin tumor has one of the most distinctive histopathologic patterns of any tumor in the body. Although the term papillary cystadenoma lympho- matosum is cumbersome, it accurately describes the salient microscopic features.
The tumor is composed of a mixture of ductal epithelium and a lymphoid stroma . The epithelium is oncocytic in nature, forming uniform rows of cells surrounding cystic spaces. The cells have abundant, finely granular eosinophilic cyto- plasm and are arranged in two layers. The inner luminal layer consists of tall columnar cells with centrally placed, palisaded, and slightly hyperchromatic nuclei. Beneath this is a second layer of cuboidal or polygonal cells with more vesicular nuclei. The lining epithelium demonstrates multiple papillary infoldings that protrude into the cystic spaces. Focal areas of squamous metaplasia or mucous cell prosoplasia may be seen. The epithelium is supported by a lymphoid stroma that frequently shows germinal center formation.
Surgical removal is the treatment of choice for patients with Warthin tumor. The procedure usually is easily accomplished because of the superficial location of the tumor. Some surgeons prefer local resection with minimal surrounding tissue; others opt for superficial parotidectomy to avoid violating the tumor capsule and because a tentative diagnosis may not be known pre- operatively. A 6% to 12% recurrence rate has been reported. Many authors, however, believe that the tumor is frequently multicentric in nature; therefore, it is difficult to determine whether these are true recur- rences or secondary tumor sites. Malignant Warthin tumors (carcinoma ex papillary cystadenoma lym- phomatosum) have been reported but are exceedingly rare.