**3.7. Mucoepidermoid carcinoma**

### *3.7.1. Definition*

**Figure 7.** a) Papillary-cystic tumor associated with a dense lymphoid stroma. b) KI 67 positive B- cell component.

Sebaceous adenoma is a benign epithelial neoplasm composed of proliferating, incompletely differentiated sebaceous glands. Sebaceous lymph adenoma is a rare variant in which the epithelial proliferation is supported by a dense lymphoid stroma and possibly arises from entrapped salivary gland tissue within intraparotid or periparotid lymph nodes (Figure 8).

Immunohistochemistry can be used to confirm the sebaceous differentiation (such as with CD15, androgen receptor, or EMA Epithelial component is cytokeratin and is EMA reactive)

a) b)

**Figure 8.** a) Sebaceous lymphadenoma b) EMA highlights the sebocytes

**3.6. Sebaceous adenoma / lymphadenoma**

314 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2

*3.6.2. Immunohistochemical stains*

*3.6.1. Definition*

[17-19]

A malignant glandular epithelial neoplasm characterized by mucus, intermediate, and epidermoid cells. This common salivary gland malignancy represents between 2% and 16% of all salivary gland tumors and up to one third of malignant salivary gland tumors.

#### **3.8. Immunohistochemical stains**

Intermediate and epidermoid cells are immunoreactive for cytokeratin and frequently EMA Three cell populations can generally be seen in MEC- epidermoid cells, mucous cells, and intermediate cells— variably set within a cystic background (Figure 9).

CK5/6, Ki-67, and p63 nuclear expression may help in the differential diagnosis. [23, 24]

**Figure 9.** a) Mucoepidermoid carcinoma(H&E) and b) CK5/6 highlight the epidermoid and intermediate cells.

### **3.9. Adenoid cystic carcinoma**

#### *3.9.1. Definition*

Adenoid cystic carcinoma accounts for 10% of all malignant salivary gland tumors. ACC is cribriform and has two prominent growth patterns: Tubular, and solid, and it is composed of epithelial and myoepithelial cells (Figure 10).

#### *3.9.2. Immunohistochemical stains*

Pseudocysts are positive for PAS, Alcian blue, laminin, and type IV collagen Epithelial cells are positive for low-molecular-weight keratins, EMA, and CD117 Myoepithelial cells are positive with calponin, SMA, S100 protein, and p63. [25 – 32].

**Figure 10.** a) Adenoid cystic carcinoma showing multiple patterns b) CD117 highlights the epithelial cells.

Polymorphous low-grade adenocarcinoma.

#### *3.9.3. Definition*

This is a malignant epithelial tumor characterized by an infiltrative growth of cytologically uniform cells ("low-grade") arranged in architecturally diverse patterns (polymorphous), slowly growing tumor that exclusively affects the minor salivary glands, most often of the palate (Figure 11).

#### *3.9.4. Immunohistochemical stains*

Cytokeratin, vimentin, and S100 protein are positive. Variable results are seen with immuno‐ histochemistry and are rarely of diagnostic value. It reacts with EMA, S-100 protein, and Bcl-2; these findings can help differentiate it from PA and ACC. [17-19, 33]

**Figure 11.** a) polymorphous low-grade adenocarcinoma b) S-100 protein

## **3.10. Epithelial-myoepithelial carcinoma**

#### *3.10.1. Definition*

a) b)

This is a malignant epithelial tumor characterized by an infiltrative growth of cytologically uniform cells ("low-grade") arranged in architecturally diverse patterns (polymorphous), slowly growing tumor that exclusively affects the minor salivary glands, most often of the

Cytokeratin, vimentin, and S100 protein are positive. Variable results are seen with immuno‐ histochemistry and are rarely of diagnostic value. It reacts with EMA, S-100 protein, and Bcl-2;

a) b)

these findings can help differentiate it from PA and ACC. [17-19, 33]

**Figure 11.** a) polymorphous low-grade adenocarcinoma b) S-100 protein

**Figure 10.** a) Adenoid cystic carcinoma showing multiple patterns b) CD117 highlights the epithelial cells.

Polymorphous low-grade adenocarcinoma.

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*3.9.3. Definition*

palate (Figure 11).

*3.9.4. Immunohistochemical stains*

Epithelial-myoepithelial carcinoma is a low-grade, malignant, biphasic salivary tumor that comprises 1% to 2% of all salivary neoplasms, the majority of which develop in the parotid gland. It is a malignant neoplasm with biphasic duct-like structures composed of an inner layer of duct lining, epithelium-type cells and an outer layer of clear, myoepithelial-type cells (Figure 12).

### *3.10.2. Immunohistochemical stains*

Inner cells are positive for keratin; outer myoepithelial cells are calponin, SMA, p63, and, less reliably, S100 protein positive; CD117 and bcl-2 are frequently positive. [17- 19, 34

**Figure 12.** a) Epithelial-myoepithelial carcinoma b) smooth muscle actin strongly stains the myoepithelial cells

## **3.11. Clear cell Carcinoma**

#### *3.11.1. Definition*

Many salivary and nonsalivary tumors contain clear cells. Among these are mucoepidermoid carcinoma, acinic cell carcinoma, oncocytoma, renal cell carcinoma, myoepithelioma, and clear cell odontogenic carcinoma.

#### *3.11.2. Immunohistochemical stains*

The neoplastic cells are positive with AE1/AE3, CAM5. 2, CK7, EMA, and p63; cells are negative with S-100 protein, calponin, actins, and GFAP (Figure 13). They are usually negative for myoepithelial markers that include S-100 protein, MSA, SMA, SMMHC, calponin, and GFAP and are also negative for CD10, CK20, vimentin, desmin, RCC, CA9, and Pax-2 see). [35-37]

**Figure 13.** a) Clear cell carcinoma b) Highlighted clear cells by S100

#### **3.12. Acinic cell carcinoma**

#### *3.12.1. Definition*

A malignant epithelial neoplasm demonstrating serous acinar cell differentiation with cytoplasmic zymogen secretory granules (Figure 14).

#### *3.12.2. Immunohistochemical stains*

PAS-positive, diastase-resistant zymogen granules. Acinic cells may stain positively for amylase, transferrin, lactoferrin, CEA, VIP, and others. About 10% show some positivity for S100 protein. [38, 39]

**Figure 14.** a) Serous acinar cells have abundant pale to basophilic, heavily granular cytoplasm (H&E). b) Trypsin is detectable in acinar cells.
