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Salivary glands

Epithelial/myoepithelial tumors

Acinic cell carcinoma


Reviewers: Fatima Aly, M.D. (see Reviewers page)
Revised: 1 February 2013, last major update August 2011
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

General
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● 1-3% of all salivary gland tumors; 3% of all parotid salivary gland tumors
● #2 childhood salivary gland malignancy after mucoepidermoid carcinoma
● Usually parotid and minor salivary glands, also parotid lymph nodes
● 10-15% metastasize (usually to local lymph nodes), 10-30% recur (may be due to inadequate excision)
● 80-90% recur if incompletely excised
● 5 year survival 90%, 20 year survival 60%
● Less aggressive in minor salivary glands

Poor prognostic factors
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● High stage, pain or fixation, gross invasion, desmoplasia, anaplasia or dedifferentiated component, increased mitotic figures, necrosis, neural invasion, incomplete resection, large size, involvement of deep lobe of parotid, multinodularity

Case reports
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● Dedifferentiation with myoepithelial features after multiple resections (Arch Pathol Lab Med 2002;126:1104)
● Dedifferentiated parotid tumor with facial nerve involvement but no prior surgery (Arch Pathol Lab Med 2004;128:e52)
● Parotid tumors in 35 year old father and his 16 year old daughter (Arch Pathol Lab Med 1999;123:1118)
● Elderly patient with mass behind ear representing metastatic tumor (Case of Week #183)

Gross description
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● Encapsulated, tan-gray, firm to soft, solid/cystic; usually < 3 cm
● 3% bilateral or multicentric

Micro description
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● At scanning power, basophillia and prominent lymphoid infiltrate should raise suspicion of acinic cell carcinoma
● Tumor shows multidirectional differentiation towards acinar, ductal as well as myoepithelial elements
● Some tumor cells must demonstrate differentiation towards acinar cells
● Variable patterns: solid, microcystic, papillary cystic (associated with hemorrhage), follicular
● Variable cell types: uniform acinar (serous) type cells with basophilic granular cytoplasm, clear cells (hypernephroid pattern, contains glycogen or mucin), vacuolated, intercalated duct, nonspecific glandular cells (smaller, syncytial)
● Few mitotic figures
● May have prominent lymphoid follicles at periphery (lymphoid stroma), psammoma bodies

Micro images
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Papillary fronds with hobnail cells and vacuolated cells


Microcystic and solid patterns in tumors from father and daughter


Figure 3A-tumor (left) and normal salivary gland (right)

       
Various images


1-dedifferentiated parotid tumor with some classic areas; 2-mitotic figures and necrosis; 3-differentiated areas with basophilic cytoplasm and vesicular nuclei; 4-PAS+ diastase resistant granules


With clear cells


D: H&E; E: CK7; F: CK20


Dedifferentiated tumor

Cytology images
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Acinar-like cells but with larger nuclei, no ducts, no fibrofatty stroma and no “bunch of grades” architecture

Positive stains
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● Keratin, alpha-1-antichymotrypsin, alpha amylase; also vasoactive intestinal polypeptide, myoepithelial markers, granules are PAS+ diastase resistant
● May have focal neuroendocrine staining

EM description
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● Multiple round, electron flocculent material with variable granule density (dependent on fixation), cytoplasmic secretory granules

Differential diagnosis
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● Normal parotid gland: tumors lack striated and interlobular ducts, lack lobular architecture
● Thyroid carcinoma

End of Salivary Glands > Epithelial/myoepithelial tumors > Acinic cell carcinoma


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