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Salivary glands

Epithelial / myoepithelial tumors

Pleomorphic adenoma


Reviewer: Adriana Handra-Luca, M.D. (see Reviewers page)
Revised: 30 January 2013, last major update September 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

General
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● Most common tumor of salivary glands
● Painless, slow growing tumor, composed of biphasic population of epithelial and mesenchymal cells
● Also called benign mixed tumor

Clinical features
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● Often women in 30ís, but any age
● 90% occur in parotid gland (represent 60% of parotid tumors; 50% occur in tail, 25% in superficial lobe, 25% in deep lobe), 10% in submandibular gland, rare in sublingual gland
● Represents 50% of salivary gland tumors of palate
● Epithelial and mesenchymal (myxoid, hyaline, chondroid, osseous) cells often arise from same cell clone (Hum Pathol 2000;31:498), which may be a myoepithelial or ductal reserve cell
● No difference in behavior based on proportion of various elements
● Risk factors for malignant transformation: submandibular location, older age, larger size, prominent hyalinization, increased mitotic rate (if present, sample tumor more thoroughly), radiation exposure

Case reports
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● 28 year old man with submandibular mass (Case of the Week #243)

Treatment
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● Wide local excision (25% recur with enucleation, 4% with adequate parotidectomy)
● Recurrences are usually within 18 months, but can be up to 50 years later (Arch Pathol Lab Med 2008;132:1445)
● After surgery for recurrent tumor, 25% recur again

Gross description
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● Well-demarcated, partially encapsulated, gray-white, myxoid, rubbery mass with solid cut surface, often 6 cm or less, tumor extensions into adjacent tissue may be subtle

Gross images
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White tumor with myxoid cut surface


Various images

Micro description
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● Not as well circumscribed as may grossly appear, with tongue like protrusions into surrounding salivary gland
● Thick capsule if present in deep parotid lobe
● Biphasic population of epithelial and mesenchymal cells
● Epithelial cells are glandular or occasionally squamous; may be spindled or oval, have large hyperchromatic nuclei
● Myoepithelial basal layer or overlying pseudoepitheliomatous hyperplasia; tumor may be very cellular
● Stroma is myxoid, hyaline, chondroid, rarely adipose tissue or osseous; mucin often present
● Occasional angiolymphatic invasion
● May have adenoid cystic pattern
● No mitotic figures, no necrosis

Micro images
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Various images

Cytology description
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● Clusters of benign epithelial cells with blue myxoid matrix and tyrosine-rich crystals

Cytology images
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Bland epithelial cells and fibrillar, metachromatically staining stroma


Various images

Positive stains
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● Ductal component: CK19, CK14, EMA, CEA, alpha-1-antitrypsin, alpha-1-antichymotrypsin, GCDFP-15, PSA (50%), PAP (50%)
● Myoepithelial component: keratin, actin, myosin, other smooth muscle proteins, S100 (particularly in cartilaginous areas), GFAP

Negative stains
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● Amylase, p53

Molecular / cytogenetics description
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● Normal or rearrangements of 8q12 or 12q14-15

Electron microscopy description
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● Features of epithelial and mesenchymal cells


Benign metastasizing mixed tumors

General
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● Controversial but distinctive clinical entity with late metastasis (6-52 years) after tumor excision to bone, CNS, kidney, liver, lung, lymph nodes, maxilla, pharynx, skin, sphenoid sinus; benign morphology in original and metastatic tumor
● Some limit diagnosis to cases in which metastasis is identical to salivary gland pleomorphic adenoma
● Rare, <50 cases reported
● 24% are incidental findings
● Mean age 33 years
● Associated with incomplete pleomorphic adenoma surgery / local recurrence, post cardiac transplant patient / immunosuppression (Mod Pathol 1998;11:1142)
● 5 year disease specific and disease free survivals of 58 and 50%
● Metastasis thought to occur via vascular channels due to tumor fragmentation or seeding at surgery
● Possible predictive features of metastatic behavior: mitoses, infiltrative growth pattern, myoepithelial cell proliferation

Case reports
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● 37 year old man with spinal cord compression after submandibular tumor (Arch Pathol Lab Med 2003;127:887)
● 48 year old man with palate tumor metastasizing to sphenoid sinus (Clin Exp Otorhinolaryngol 2010;3:172)
● 53 year old woman with solitary kidney mass and subsequent parotid mixed malignant tumor (Am J Surg Pathol 2000;24:1159)

Treatment
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● Surgery; radio- or chemotherapy of limited value (Arch Otolaryngol Head Neck Surg 2006;132:788)

Micro images
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Sphenoid sinus metastasis from palate


Spinal cord metastasis from submandibular tumor (MRI and H&E)

Stains
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● PR+, ER- in both tumor components (J Med Assoc Thai 2009;92:1250); also p53, bcl2, Ki-67
● Also CD105, p21

Molecular / cytogenetics description (?)
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● May be diploid, hyopodiploid or aneuploid (Cancer Genet Cytogenet 1998;102:59, Rev Stomatol Chir Maxillofac 1996;97:26)
● 3p deletions

End of Salivary glands > Epithelial / myoepithelial tumors > Pleomorphic adenoma


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