Morphological Classification of Oral Carcinoma
Oral carcinomas are primarily classified as squamous cell carcinomas, which can be further categorized based on histological features into several distinct subtypes that impact prognosis and treatment decisions. 1
Squamous Cell Carcinoma Subtypes
The World Health Organization (WHO) classification system recognizes the following subtypes of oral squamous cell carcinoma:
- Keratinizing type - Characterized by the presence of keratin pearls
- Nonkeratinizing type - Can be further subdivided into:
- Large cell variant
- Small cell variant
- Verrucous carcinoma - A well-differentiated variant with low metastatic potential
- Warty (condylomatous) carcinoma
- Papillary squamous cell (transitional) carcinoma
- Lymphoepithelioma-like carcinoma
- Basaloid squamous cell carcinoma - An aggressive variant with poor prognosis
- Adenoid basal carcinoma/epithelioma 1
Histological Grading
While histopathologic grading for squamous cell carcinoma has shown inconsistent correlation with prognosis, it remains an important descriptive feature:
- Grade 1 - Well-differentiated
- Grade 2 - Moderately differentiated
- Grade 3 - Poorly differentiated 1
For adenocarcinomas of the oral cavity, grading is based on architectural patterns and cytologic criteria:
- Grade 1 - Well-differentiated (≤10% solid growth)
- Grade 2 - Moderately differentiated (11-50% solid growth)
- Grade 3 - Poorly differentiated (>50% solid growth) 1
Tumor Invasion Assessment
The assessment of invasion depth and pattern is critical for staging and prognosis:
- Depth of invasion - Measured in millimeters from the basement membrane
- Interface with stroma - Can be infiltrating or pushing
- Pattern of invasion - Including:
- Superficial or deep invasion
- Invasion of adjacent structures 1
TNM Staging System
The TNM staging system for oral cavity cancers is based on:
T (Tumor size and local invasion):
- Tis: Carcinoma in situ
- T1: ≤2 cm in greatest dimension
- T2: >2 cm but ≤4 cm
- T3: >4 cm
- T4: Invasion of adjacent structures 2
N (Regional lymph node involvement):
- Assessed through physical examination and imaging
- Extranodal spread is an important prognostic factor 1
M (Distant metastasis):
- Evaluated primarily through chest imaging 2
Important Morphological Features for Prognosis
Several morphological features have significant prognostic implications:
- Depth of invasion - A key parameter in the 8th edition of the AJCC staging system
- Extranodal extension - Indicates aggressive behavior
- Perineural invasion - Associated with poor prognosis
- Lymphovascular invasion - Indicates higher risk of metastasis 2
Practical Considerations
When examining oral carcinoma specimens:
- Measure tumor in three dimensions
- Describe shape (ulcerating, exophytic, polypoid)
- Document multifocal growth if present
- Assess invasion of adjacent structures carefully, particularly bone invasion
- For lymph node dissections, document number of nodes, size of metastatic deposits, and presence of extranodal extension 1
The morphological classification of oral carcinomas is essential for determining prognosis and guiding treatment decisions. Accurate histopathological assessment and reporting using standardized terminology ensures optimal patient management.