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Salivary glands

Epithelial / myoepithelial tumors

Polymorphous low grade adenocarcinoma


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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● Common tumor of palate with infiltrative growth, multiple architectural growth patterns and cellular uniformity, first described in 1983 (Oral Surg Oral Med Oral Pathol 1983;56:157)
● Also called terminal duct carcinoma, lobular carcinoma, low grade papillary adenocarcinoma
● 10% of minor salivary gland tumors but only 1% of all malignant salivary gland tumors

Clinical features
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● #2 most common palate tumor (after adenoid cystic carcinoma); less common in Japanese
● In major salivary glands, usually associated with pleomorphic adenoma
● Median age 54 years, range 22-71 years, 2/3 women
● Rare in teenagers, but aggressive
● Slow growing, not painful
● More than focal papillary growth is associated with cervical nodal metastases
● Difficult diagnosis on biopsy, frozen section or fine needle aspiration (Arch Pathol Lab Med 2009;133:1763)

Treatment
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● Conservative wide excision
● 9-30% recur, nodal metastases in 9-15%, 10% have distant metastases (lung) or tumor related death
● Long term follow-up required (Am J Surg Pathol 2000;24:1319)
● Positive or unknown surgical margins are associated with local recurrence

Gross description
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● Exophytic, may be ulcerated
● Average size 2 cm

Micro description
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● Triad of infiltrative growth, multiple architectural growth patterns, cellular uniformity
● Nonencapsulated but often well circumscribed tumor with diverse (polymorphous) growth patterns (cribriform, fascicular, microcystic, mixed, papillary [focal], pseudoadenoid cystic [without true lumens], single file, solid, strand-like, tubular) (Am J Surg Pathol 1984;8:367)
● Infiltrative borders as small islands and tubules
● Mucoid and hyaline stroma (may contain calcifications)
● Cells have only mild atypia with uniform, bland nuclei (occasional mucus, clear or oncocytic cells), but with perineurial invasion (prominent, frequent, targetoid pattern) common around small nerves
● No/rare mitotic figures, rare tumor necrosis
● High grade transformation shows atyipia, necrosis, mitoses, MIB index, p53 overexpression

Micro images
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Various images


Low grade features


Polymorphous patterns


H&E, CK7 and CK20


H&E, CD117, galectin 3

Positive stains
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● CK7, CK8, CK14, p63, EMA (luminal and nonluminal cells), S100 (Am J Surg Pathol 1988;12:461), galectin3 (cytoplasmic, Mod Pathol 2002;15:687), vimentin
● Focal CEA
● Also membrane E-cadherin, kallikrein8, kallikrein13, osteopontin, beta-6, tenascin C, MMP1, intense catepsin, maspin, MCM2, COX2, beta-catenin (nuclear and cytoplasmic), DNMT1 (DNA methytransferase)
● Also laminin, collagen IV, fibronectin positive stroma

Negative stains
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● Myoepithelial markers (alpha smooth muscle actin, smooth muscle myosin heavy chain, calponin), CD117 (may be weak, Mod Pathol 2003;16:1224), GFAP negative/low, CK13, CK19, CK20, kallikrein3, E2F1, PLUNCs, cyclin D1
● No HER2 overexpression

Molecular / cytogenetics description
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● Diploid, but chromosome 12 abnormalities
● No t(11,19)
● 6q, 11q deletions in metastatic cases, few copy number alterations

Differential diagnosis
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Adenoid cystic carcinoma: bilayered tubules, nuclear atypia, CD117+, CK5/7+, cyclin D1+, galectin3+, luminal EMA, weak vimentin S100 and CEA, higher Ki67 and MCM2; also positive for myoeptihelial markers, methallothionin; cytokeratin/integrin pattern of apical luminal positivity vs bipolar pattern in PLGA (Mod Pathol 2008;21:105)
Basal cell adenoma
Carcinoma ex-pleomorphic adenoma / malignant mixed tumor
Cystadenocarcinoma has papillary areas but prominent cystic areas
Epithelial-myoepithelial carcinoma
● Metastatic lobular breast carcinoma: see Arch Pathol Lab Med 2000;124:157
● Monomorphous adenoma
Papillary adenocarcinoma (low grade)
Pleomorphic adenoma: circumscribed, no perineurial invasion, although both may extend focally into adjacent minor salivary glands

End of Salivary glands > Epithelial / myoepithelial tumors > Polymorphous low grade adenocarcinoma


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