PATHOLOGY CLINIC

Mucoepidermoid carcinoma

Lester D.R. Thompson, MD

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-1 . •, • . A· ~;J. ~ # ,. r:;;; ~ c rV" ~ i} ...... l1.lG;y;t; ~ ~ ml· !' ~ ~ tJ " Figure. A: A blending of intermediate, pavemented cells and goblet-type, mucus-filled cells is characteristic ofan MEC. B: Cystic spaces are common in low-grade tumors. This MEC has an intermediate cell population and many mucocytes. Inset: An MEC demonstrates a strong reaction on a mucicarmine stain.

Mucoepidermoid carcinoma (MEC) is the most com• Cysts of variable sizes are often present, and they usually mon primary salivary gland malignancy, accounting for contain brownish fluid. MEC cells form sheets, islands, approximately 25% of all malignancies. More than half duct-like structures, and cysts of various sizes . The cysts of these cases involve the major saliva ry glands, primarily may be lined with intermediate, mucous , or epidermoid the parotid glands. MEC can also involve a variety of other cells, and they are filled with mucus (figure, A). Papillary sites that have minor mucoserous glands .Women are more processes may extend into the cyst lumina, and this is oc• commonly affected than men (3:2), and the mean age at casionally a conspicuous feature. onset is in the 5th decade of life. MEC is also the most The tumor is primarily made up of three cell types in common salivary gland malignancy in children. widely varying proportions: intermediate, mucous, and The tumor usually forms as a painless, fixed, slowly epidermoid. growing swelling of widelyvarying duration thatsometimes goes through a phase of accelerated growth immediately • The intermediate cells frequentl y predominate; their before clinical presentation. Symptoms include tender• appearance ranges from small basal cells with scanty ness, otorrhea, dysph agia, and trismus. Intraoral tumors basophili c cytopl asm to larger and more oval cells with are often bluish-red and fluctuant, and they may resemble more abundant pale eosinophilic cytoplasm that appears mucocele s or vascular lesions . They occasionally invade to merge into epidermoid or mucous cells . the underlying bone . • Mucou s cells (mucocytes) can occur singly or in clus• MECs may be circum scribed and variably capsulated or ters, and they have pale and sometimes foamy cytoplasm, infiltrative and fixed;the latter characteristics generally ap• a distinct cell boundary, and small, peripherally placed, ply to higher-grade tumors .Areas of scarring are relatively compressed nuclei . Mucocytes often form the lining of common. Most tumors are smaller than 4 em in diameter. cysts or duct-like structures (figure, B). Occasionally

From the Department of Pathology, Woodl and Hills Medical Center, Southern California Permanente Medical Group, Woodland Hills, Calif.

762 ENT-Ear, Nose & Throat Journal· De cem ber 2005 PATHOLOG Y CLINIC mucocytes are so scanty that they can be identified with The prognosis is dependent on the clinical stage, site, confidence only by using stains such as mucicarmine grading, and adequacy of surgery. Survival is greater than (figure, B, inset). 95% for low-grade tumors,and regional metastasesare rare. • Epidermoid cells may be uncommon and focally dis• The death rate increases to 45% for high-grade tumors. tributed. They have abundant eosinophilic cytoplasm, but Tumors that transgress surgical margins have a very high they rarely show keratin pearl formation or dyskeratosis. recurre nce rate, particularly high-grade tumors. Death Oncocytic metaplasia is seen occasionally. is usually caused by uncontrolled locoregional disease and metastases to the lung, bone, and brain. Treatmen t is Higher-grade tumors show evidence ofcytologic atypia, surgical excision with or without neck dissection. Radio• a high mitotic frequency, and areas of necrosis, and they are therapy is generally palliative in advanced tumors; it has more likely to show neural invasion.Stromal hyalinization little impact on prognosis. is common and sometimes extensive. MECs exhibit remarkable variability in their clinical Suggested reading behavior. Several microscopic grading systems based on a Brandwein MS, Ivano v K,Wallace 01 ,et al. Mucoepidermoidcarcinoma: numeric al score have been advocated as a means of predict• A clinicopathologic study of 80 patients with special reference to histological grading. Am J Surg Pathol 2001;25:835-45. ing outcome. These systems rely on subjec tive evalu ations Goode RK,A uclairPL,EllisGL. Mucoepidermoid carcinoma oft he major of the relative proportions of the various cell types, the salivary glands: Clinical and histopathologic analysis of234 cases degree of cellular atypia, mitotic frequency, presence of with evaluation of grading criteria. Cancer 1998;82:1217-24. necrosis, and invasive characteristics. Goode RK, El-Naggar AK. Mucoep idermoid carcinoma. In: Barnes EL, Michael L, eds. Pathology and Genetics of Tumours of the MECs must be distinguished from necrotizing sialometa• Head and Neck . Kleihues P, Sobin LH, series eds. World Health plasia, chronic sialadenitis, cystadenoma, cystadenocarci• Organization Classification of Tumours. Lyon, France: IARC noma, squamous cell carcinoma, epithelial-myoepithelial Press, 2005 :227-8. carcinoma, clear cell carcinoma (not otherwise specified), and metastatic tumors. ATTENTION LARYNGOLOGISTS How would you like to increase OR time by decreasing set-up time?

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