Salivary Tumors

The Salivary Glands: Comparison of Histologies

Grade Histology local-regional recurrence LN(+) at presentation Distant Metastasis Standard Therapy OS-5
Low mucoepidermoid, of parotid glands 5-6% S
Low mucoepidermoid, low-grade 15% rare S
Low Pleomorphic adenoma 22% S
High mucoepidermoid, of minor salivary glands 30% S + RT (bed+ LN)
High mucoepidermoid, high-grade 60% 44-55 33% S + RT (bed + LN)
High Adenocarcinoma 23% 56% 44% S + RT (bed + LN) 30%
High Squamous of parotid 50-60% S + RT (bed + LN)
Other Adenoid cystic 7.5% initially 40-50% S + RT (bed + Nerve)
  • S: Surgery (parotidectomy)
  • bed: Tumor bed
  • LN: Regional Lymph nodes
  • Nerve: Cranial nerve to base of skull

SUMMARY OF HISTOLOGY

table

PERCENT WITH POSTIVE LYMPH NODE PRESENTATION

Low-risk (10%)

  • acinic
  • adenoid cystic
  • carcinoma ex pleomorphic adenoma

Intermediate-Risk(30%)

  • mucoepidermoid with

High-risk (50%)

  • other high-grade tumors
  • especially SCCA and undifferentiated tumors

HISTOLOGY

histology

MIXED TUMORS

Benign

  • Benign Mixed Tumor: Also called Pleomorphic adenoma, other names include "mixed tumor, salivary gland type"
    • characterized by an admixture of polygonal epithelial and spindle-shaped myoepithelial elements in a variable background stroma that may be mucoid, myxoid, cartilaginous or hyaline.
    • 75% of benign tumors and more than 50% of all parotid neoplasms.
  • pleomorphicadenoma

Low-Grade

  • Epithelial-myoepithelial carinoma is a salivary gland malignancy composed of an inner layer of ductal cells surrounded by a layer of clear myoepithelial cells. They usually have well circumscribed peripheral margins (A). Classic form is a double cell proliferation composed of a darker inner layer of ductal cells associated with a prominent outer layer of clear myoepithelial cells accentuated by immunostain for calponin (inset) (B). Variations including sclerotic (hyalinizing) (C) and clear cell dominant (ductal poor) (D) mophologies.
  • epithelial

High-Grade

  • Malignant mixed
  • also called Carcinoma ex pleomorphic adenoma
    • malignant transformation from Pleomorphic adenoma
    • Carcinosarcoma arising de novo is a distinct type of malignant mixed tumor.
    • adenocarcinoma is the most common histologic subtypes of carcinom ex pleomorphic adenoma

EPITHELIAL TUMORS

Benign

  • Basal Cell Adenoma (a type of Monomorphous adenoma)

Low-Grade

  • Basal cell adenocarcinoma
  • Low-grade Adenocarcinoma
  • polymorphous low-grade adenocarcinoma (PLGA) - a type of low-grade Adenocarcinoma
    • resemble pleomorphic adenoma and adenoid cystic carcinoma
    • also called terminal duct adenocarcinoma, lobular carcinoma, papillary low-grade adenocarcinoma and trabecular adenocarcinoma.

High-Grade

  • Adenoid cystic
    • invasive tumor composed of basaloid cells with cribriform, tubular or solid growth pattern, and excessive myxohyaline stroma.
  • Adenocarcinoma
  • SCCA
  • Anaplastic
  • Undifferentiated
  • salivary duct carcinomas
    • Highly aggressive tumor with solid, papillary, solid and cribriform patterns, that resemble in situ and invasive ductal carcinoma of the breast.
adnoidcystic

A+B: Adenoid cystic showing cribriform growth pattern and tumor cell nests.
E: solid-type adenoid cystic carcinoma with mitoses and central necrosis

  • Invasive tumor composed of basaloid cells with cribriform, tubular or solid growth pattern, and excessive myxohyaline stroma.
  • The one important thing to remember that is particularly frustrating is that distant metastases can develop in up to 50% of patients. Survival is about 75% at five years but drops to as low as 25% at 15-20 years. It is almost like a systemic disease with an unpredictable clinical course.

C+D: Polymorphous low-grade adenocarcinoma (PLGA) with infiltration into fat and perineural space
F: PLGA showing a tubule lined by a single layer of cuboid, monomorphic tumor cells with round, vesicular nuclei containing indistinct nucleoli.

SEROUS OR MUCINOUS ACINIC TUMORS

Low-Grade

  • Low-grade mucodepidermoid
    • Epithelial malignant tumor composed of mucous, intermediate and epidermoid cells.
    • Since most of this lesion is cystic and there is orderly production of mucin, this component would be classified as a low grade mucoepidermoid carcinoma.
  • LGME
  • acinic cell carcinoma
    • Salivary gland tumor with acinar cell differentiation.
    • second most common malignant tumors of the parotid gland

High-Grade

  • High-grade mucoepidermoid
    • Epithelial malignant tumor composed of mucous and epidermoid cells.
  • High-grade Acinic: Acinic cell carcinoma resemble serous acinar cells vary in their behavior from locally aggressive to blatantly malignant (most are low-grade). Prognosis is good a) 5-yr survival rate is 89%. b) 20-yr survival rate is 56%.
  • acinic1

LYMPHOID TUMORS

Benign

  • Adenolymphoma (Warthin's Tumor): also called Papillary Cystadenoma Lymphomatosum
    • also called adenolymphoma
    • 2-6% of all parotid tumors
  • Benign Lymphoepithelial Lesions (Godwin's Tumor)

High-Grade

  • Lymphoepithelioma (Malignant Lymphoepithelial Lesions)
    • Rare malignant epithelial tumor, considered a subtype of the undifferentiated carcinomas, composed of islands of atypical, large, epithelial cells accompanied by a benign dense lymphoplasmacytic infiltrate.

OTHER BENIGN TUMORS

  • Oncocytoma
    • slow-growing tumor found mostly in the older age group.
    • The encapsulated tumor has a dark appearance similar to melanoma.

ADENOID CYSTIC CARCINOMA OF PAROTID

INCIDENCE

  • 10-15% of all salivary neoplasms, most common sites: minor salivary glands (60%) and parotids (25%)

HISTOLOGY

  • 3 patterns: cribiform (higher local recurrence), tubular, and solid.
  • Note that pleomorphic adenoma can be confused with ACC on FNA.

NATURAL HISTORY

  • It is a slow growing, indolent tumor, but highly aggressive.
    • Need long (15 yr) follow up due to late relapses.
    • Lymph node mets are rare
    • Distant failure to lung and bone is common.
  • 50% have Perineural invasion (a characteristic finding).

TREATMENT

  • Optimal treatment regimens have not yet been identified, but surgery and adjuvant RT are recommended.
  • No known chemotherapy agents are known to be effective.
  • RT is most useful when margins are + or perineural invasion is present (even if not seen in path specimen).
  • There are no randomized trials.
Unless otherwise stated, the content of this page is licensed under Creative Commons Attribution-Share Alike 2.5 License.