Adenoid Cystic Carcinoma

🧬 Adenoid Cystic Carcinoma

🧠 Definition of Adenoid Cystic Carcinoma

Adenoid cystic carcinoma is a malignant epithelial salivary gland tumor that is slow growing yet highly aggressive, with a marked tendency for recurrence and perineural invasion.

• Most common malignant tumor of the submandibular gland

• Accounts for ~ 10% of all salivary gland tumors

• Common age group: 5th–7th decade

• Female preponderance

What is Neurotropism?

What is the other name of Adenoid Cystic Carcinoma?

Which is the most common malignant salivary gland tumor?

Which is the second most common malignant salivary gland tumor?

🧬 Histogenesis of Adenoid Cystic Carcinoma

Explained by the Reserve Cell (Stem Cell) Theory:

• Tumor arises from pluripotent reserve cells of intercalated ducts

• These differentiate into:

  • Ductal cells
  • Myoepithelial cells

What are the Genetic Alterations seen in Adenoid Cystic Carcinoma?

🔍 Histology of Adenoid Cystic Carcinoma

Gross Features

• Poorly encapsulated tumor

• Firm, gray-white

• Cut section shows solid tumor with small cystic spaces

What is characteristic appearance seen in Adenoid Cystic Carcinoma?

Microscopic Features

Tumor consists of ductal cells + myoepithelial cells arranged in three patterns:

🧀 Histological Patterns of Adenoid Cystic Carcinoma

• Cribriform
• Tubular
• Solid

🚩 Most tumors show mixed patterns – classification depends on the predominant pattern

Which is the most common Histological Patterns of Adenoid Cystic Carcinoma?

Which is the most aggressive Histological Patterns of Adenoid Cystic Carcinoma? Why?

What is the Histological Grading of Adenoid Cystic Carcinoma?

📍 Sites of Involvement of Adenoid Cystic Carcinoma

• Minor salivary glands

• Major salivary glands:

  • Parotid: 20–25%
  • Submandibular: 10–15%
  • Sublingual: ~5%

What is the most common site of involvement of Adenoid Cystic Carcinoma?

What is the most common site of involvement of Adenoid Cystic Carcinoma in minor salivary glands?

🩺 Clinical Features of Adenoid Cystic Carcinoma

• Slow-growing, firm mass

• Pain occurs early (important malignant feature)

• Progressive numbness

• Facial nerve palsy (parotid involvement)

• Fixation to deeper structures

• Surface ulceration

What is Neurotropism? What is it's implications in spread of Adenoid Cystic Carcinoma?

Metastasis

• Regional lymph nodes – rare

• Distant metastasis:- Lung, Bone, Liver

What is the most common site of distant metastasis in Adenoid Cystic Carcinoma?

🔎 Investigations of Adenoid Cystic Carcinoma

• Ultrasound – first line, FNAC guidance

• FNAC – diagnostic

• Biopsy – confirms pattern, grade, perineural invasion

• MRI (Gold standard)

• CT scan – bone involvement

• PET-CT – staging and distant metastasis

🏥 Treatment of Adenoid Cystic Carcinoma

🔪 Surgery (Mainstay)

• Wide local excision / total gland excision
• Bone resection if involved (palate, mandible, maxilla)
• Facial nerve preserved unless infiltrated

🦴 Neck Dissection

• Clinically node-positive → Therapeutic neck dissection

• Clinically N0 → Usually not done

What are the indications of Neck Dissection in Clinically N0 neck in Adenoid Cystic Carcinoma?

What are the indications of Adjuvant Radiotherapy in Adenoid Cystic Carcinoma?

💊 Chemotherapy in Adenoid Cystic Carcinoma

• Very limited role
• Mainly palliative
• Drugs with temporary response:
  • Cisplatin
  • Doxorubicin
  • Cyclophosphamide

📉 Prognosis of Adenoid Cystic Carcinoma

Poor Prognostic Factors

• Solid histological pattern (Grade 3)
• Perineural invasion
• Vascular invasion
• Positive margins
• Advanced stage
• Submandibular / sublingual involvement

Survival Rates

• 5-year survival: 60–75%
• 10-year survival: 30–50%

📌 Exam Pearls

• Slow growing but aggressive = Adenoid cystic carcinoma
• Swiss cheese appearance
• Perineural invasion → skip lesions
• Solid pattern = worst prognosis
• Most common malignancy of submandibular gland