Salivary gland pathology | Gastrointestinal pathology | Pathology

Salivary gland pathology

Tumors: Most salivary gland tumors are benign. Skin cancers may metastasize to the salivary glands.

Most parotid gland tumors are benign, while roughly half of minor salivary gland tumors are malignant. The following are common benign tumors of the salivary glands:

i) Pleomorphic adenoma: It arises from intercalated stem cells of the parotid gland. Pleomorphic adenoma is the most common parotid gland tumor and is seen more often in middle-aged women. Prior radiation exposure is a risk factor. It presents as a slow-growing, painless mass. On gross examination, it is pseudo-encapsulated, smooth, lobulated, and greyish-blue, with a semi-translucent cut surface. Microscopically, it shows a “pleomorphic” mixture of epithelial (ductal) cells, myoepithelial cells, and chondromyxoid stroma. Treatment is local surgical resection. Local recurrence is common even after surgical resection.

ii) Warthin’s tumor: This is a benign tumor seen most commonly in the parotid gland in middle-aged to older men. It often presents as bilateral parotid tumors. It arises from lymphoid tissue and is often associated with TB and brucellosis. On gross examination, the tumor is encapsulated, with cystic spaces filled with milky fluid and hemorrhagic areas. Microscopically, it shows a characteristic double layer of epithelial cells resting on dense lymphoid stroma with germinal centers, along with cystic spaces and polypoid projections. Rarely, signet or goblet cells and areas of squamous metaplasia may be seen. No myoepithelial elements are present.

The following primary malignant tumors are seen in the salivary glands:

i) Mucoepidermoid carcinoma: This is the most common malignant tumor of the salivary glands and mainly affects the parotid gland. Radiation exposure carries a high risk of developing mucoepidermoid tumors. The tumor arises from excretory stem cells. It is associated with t(11;19), resulting in formation of the MECT1 gene, which causes unregulated growth and inhibition of apoptosis. Microscopically, it shows a mixture of mucinous, squamous, intermediate, and clear cells with local infiltration. Metastases to regional lymph nodes may be seen.

ii) Adenoid cystic carcinoma or cylindroma: This tumor is associated with NOTCH1 and NOTCH2 mutations. It arises from intercalated stem cells of the minor salivary glands. It characteristically infiltrates along nerve sheaths. Pulmonary metastases may be seen. Microscopically, tubular or cribriform patterns are seen, with myoepithelial elements.

iii) Acinic cell carcinoma: It arises from intercalated stem cells of the parotid gland. Cells are arranged in acini or sheets and have basophilic cytoplasm.

iv) Polymorphous adenocarcinoma: It arises from intercalated ductal cells of the minor salivary glands. Microscopy is typical of other adenocarcinomas, with glandular structures.

v) Squamous cell or epidermoid carcinoma: It arises from excretory stem cells in the parotid and submandibular glands. Skin infiltration and keratin formation are seen. Metastases to regional lymph nodes in the neck area may occur.

vi) Non-Hodgkin lymphoma: Locally infiltrating lymphocytes can progress to NHL. Some cases of Sjogren’s syndrome may develop NHL.
Primary Sjogren’s syndrome: This is an autoimmune disorder that affects the salivary and lacrimal glands and is more common in females. It causes xerostomia and xerophthalmia (keratoconjunctivitis sicca) due to loss of gland cells. Aberrant local activation and proliferation of B cells causes Sjogren’s syndrome. Sjogren’s syndrome is often associated with rheumatoid arthritis.
Mikulicz syndrome: This is a chronic inflammatory disorder characterized by enlargement of the salivary and lacrimal glands. It is often associated with TB, Hodgkin’s disease, syphilis, leukemia, and SLE. It is more common in females. It presents with recurrent fevers, xerophthalmia, and xerostomia.
Infections of the salivary glands: Mumps virus causes epidemic parotitis of the parotid glands. Other viruses, such as HIV, Hep C, and Coxsackie viruses, can also cause parotitis. Bacterial parotitis with S.aureus or Streptococci is seen in DM, immunodeficiencies, and post-surgery settings. It presents with local swelling, pain, and fever.

Acute sialadenitis (inflammation of the salivary glandular ducts) is commonly precipitated by stones (sialolithiasis). In recurrent cases, or if an abscess develops, imaging may be done using sialography, ultrasound, CT, MRI, or PET scan.

Chronic inflammation in the salivary glands is seen with chronic sialolithiasis, strictures, autoimmune disorders, TB or fungal infections, sarcoidosis, and syphilis. It can be visualized by contrast-enhanced CT or MRI.
Sialolithiasis: Sialolithiasis is stone formation in the salivary ducts. It presents with postprandial swelling of the salivary gland, pain that worsens with meals, and decreased salivary secretion. Some stones can be palpated. Sialolithiasis is more common in the submandibular gland because its secretions tend to stagnate due to duct location, and because its mucinous, alkaline secretions promote calcium precipitation. It is assessed with sialography, non-contrast CT scans, MRI, or ultrasound.

Salivary gland pathology

Tumors: Most salivary gland tumors are benign. Skin cancers may metastasize to the salivary glands.

Most parotid gland tumors are benign, while roughly half of minor salivary gland tumors are malignant. The following are common benign tumors of the salivary glands:

i) Pleomorphic adenoma: It arises from intercalated stem cells of the parotid gland. Pleomorphic adenoma is the most common parotid gland tumor and is seen more often in middle-aged women. Prior radiation exposure is a risk factor. It presents as a slow-growing, painless mass. On gross examination, it is pseudo-encapsulated, smooth, lobulated, and greyish-blue, with a semi-translucent cut surface. Microscopically, it shows a “pleomorphic” mixture of epithelial (ductal) cells, myoepithelial cells, and chondromyxoid stroma. Treatment is local surgical resection. Local recurrence is common even after surgical resection.

ii) Warthin’s tumor: This is a benign tumor seen most commonly in the parotid gland in middle-aged to older men. It often presents as bilateral parotid tumors. It arises from lymphoid tissue and is often associated with TB and brucellosis. On gross examination, the tumor is encapsulated, with cystic spaces filled with milky fluid and hemorrhagic areas. Microscopically, it shows a characteristic double layer of epithelial cells resting on dense lymphoid stroma with germinal centers, along with cystic spaces and polypoid projections. Rarely, signet or goblet cells and areas of squamous metaplasia may be seen. No myoepithelial elements are present.

The following primary malignant tumors are seen in the salivary glands:

i) Mucoepidermoid carcinoma: This is the most common malignant tumor of the salivary glands and mainly affects the parotid gland. Radiation exposure carries a high risk of developing mucoepidermoid tumors. The tumor arises from excretory stem cells. It is associated with t(11;19), resulting in formation of the MECT1 gene, which causes unregulated growth and inhibition of apoptosis. Microscopically, it shows a mixture of mucinous, squamous, intermediate, and clear cells with local infiltration. Metastases to regional lymph nodes may be seen.

ii) Adenoid cystic carcinoma or cylindroma: This tumor is associated with NOTCH1 and NOTCH2 mutations. It arises from intercalated stem cells of the minor salivary glands. It characteristically infiltrates along nerve sheaths. Pulmonary metastases may be seen. Microscopically, tubular or cribriform patterns are seen, with myoepithelial elements.

iii) Acinic cell carcinoma: It arises from intercalated stem cells of the parotid gland. Cells are arranged in acini or sheets and have basophilic cytoplasm.

iv) Polymorphous adenocarcinoma: It arises from intercalated ductal cells of the minor salivary glands. Microscopy is typical of other adenocarcinomas, with glandular structures.

v) Squamous cell or epidermoid carcinoma: It arises from excretory stem cells in the parotid and submandibular glands. Skin infiltration and keratin formation are seen. Metastases to regional lymph nodes in the neck area may occur.

vi) Non-Hodgkin lymphoma: Locally infiltrating lymphocytes can progress to NHL. Some cases of Sjogren’s syndrome may develop NHL.
Primary Sjogren’s syndrome: This is an autoimmune disorder that affects the salivary and lacrimal glands and is more common in females. It causes xerostomia and xerophthalmia (keratoconjunctivitis sicca) due to loss of gland cells. Aberrant local activation and proliferation of B cells causes Sjogren’s syndrome. Sjogren’s syndrome is often associated with rheumatoid arthritis.
Mikulicz syndrome: This is a chronic inflammatory disorder characterized by enlargement of the salivary and lacrimal glands. It is often associated with TB, Hodgkin’s disease, syphilis, leukemia, and SLE. It is more common in females. It presents with recurrent fevers, xerophthalmia, and xerostomia.
Infections of the salivary glands: Mumps virus causes epidemic parotitis of the parotid glands. Other viruses, such as HIV, Hep C, and Coxsackie viruses, can also cause parotitis. Bacterial parotitis with S.aureus or Streptococci is seen in DM, immunodeficiencies, and post-surgery settings. It presents with local swelling, pain, and fever.

Acute sialadenitis (inflammation of the salivary glandular ducts) is commonly precipitated by stones (sialolithiasis). In recurrent cases, or if an abscess develops, imaging may be done using sialography, ultrasound, CT, MRI, or PET scan.

Chronic inflammation in the salivary glands is seen with chronic sialolithiasis, strictures, autoimmune disorders, TB or fungal infections, sarcoidosis, and syphilis. It can be visualized by contrast-enhanced CT or MRI.
Sialolithiasis: Sialolithiasis is stone formation in the salivary ducts. It presents with postprandial swelling of the salivary gland, pain that worsens with meals, and decreased salivary secretion. Some stones can be palpated. Sialolithiasis is more common in the submandibular gland because its secretions tend to stagnate due to duct location, and because its mucinous, alkaline secretions promote calcium precipitation. It is assessed with sialography, non-contrast CT scans, MRI, or ultrasound.