Comprehensive Study Notes on Epithelial Neoplasms of the Oral Cavity

Definition and Nature of Neoplasia

• Biological Phenomenon: Neoplasia is a complex biological process that is sometimes difficult to differentiate from other tissue reactions or processes.

• Willis Definition (1952): A neoplasm is defined as an abnormal mass of tissue, the growth of which exceeds and is uncoordinated with that of the normal tissues and persists in the same excessive manner after cessation of the stimuli that evoked the change.

• Clinical Significance: While oral neoplasms constitute a small percentage of conditions seen by dentists, they are critical due to their potential to jeopardize the health and longevity of the patient. Familiarity with these lesions is essential for appropriate treatment or specialist referral.

Benign Neoplasms of Epithelial Tissue Origin

Squamous Papilloma

• Etiology: Associated with the Human Papilloma Virus (HPV), specifically types $6$ and $11$. These types are not typically demonstrated in oral malignancies or potentially malignant lesions.

• Epidemiology:

  • Fourth most common oral mucosal mass.

  • Found in $1$ out of every $1000$ individuals.

  • Accounts for $3\%-4\%$ of all biopsied oral soft tissue lesions.

  • More common in males and the white race.

• Infectivity: Extremely low virulence and infectivity rate; generally not considered contagious.

• Clinical Features:

  • Exophytic growth with numerous finger-like projections (cauliflower-like or verrucous surface).

  • Usually pedunculated, occasionally sessile, well-circumscribed, and painless.

  • Color is white or pink.

  • Common sites: Tongue, lips, buccal mucosa, gingiva, and palate (near the uvula).

  • Size: Usually a few millimeters, but can reach several centimeters.

  • Age: Most common between $30$ and $50$ years, and in children under $10$.

• Histology:

  • Long, thin, finger-like projections of stratified squamous epithelium supported by a thin central connective tissue core.

  • Proliferation of spinous cells in a papillary pattern.

  • Secondary hyperkeratosis may occur due to trauma.

  • Koilocytes: HPV-altered cells with perinuclear clear spaces and nuclear pyknosis may be present. Koilocytes are HPV-altered cells distinguished by two key features: - **Perinuclear Clear Spaces**: These clear areas surrounding the nucleus are indicative of cellular changes associated with HPV infection. - **Nuclear Pyknosis**: This refers to the condensing of the nucleus and is another hallmark of koilocytotic changes. Koilocytes are typically found in epithelial tissues, particularly in lesions associated with HPV, such as squamous papillomas and low-grade squamous intraepithelial lesions (LSILs). They are often observed in the surface layers of the epithelium, where the viral pathology manifests.

• Treatment: Excision including the base; recurrence is rare if properly removed.

Verruca Vulgaris (Common Wart)

• Etiology: Associated with HPV subtypes $2$, $4$, and $40$.

• Clinical Features:

  • Common on skin, uncommon on oral mucosa (except lips).

  • White, verrucous surface with a narrow stalk.

  • Growth is rapid, seldom exceeding $5\,mm$.

  • Autoinoculation: Highly contagious; spreads to lips/mouth through finger sucking or nail biting.

• Treatment: Surgical excision, curettage, liquid nitrogen cryotherapy, or topical keratinolytic agents (salicylic/lactic acid).

Multiple Hamartoma and Neoplasia Syndrome (Cowden Syndrome)

• Nature: Autosomal dominant disease.

• Manifestations: Facial trichilemmomas, oral papillomatous or "pebbly" lesions/fibromas, associated with abnormalities in the gastrointestinal tract, thyroid, CNS, and musculoskeletal system.

Squamous Acanthoma

• Nature: Likely a reactive phenomenon caused by trauma rather than a true neoplasm.

• Clinical Features: Small, flat or elevated, white, sessile or pedunculated lesion in older adults.

• Histology: Well-demarcated elevated/umbilicated epithelial proliferation with a thickened orthokeratin layer.

Keratoacanthoma (KA)

• Nature: Low-grade malignancy originating in pilosebaceous glands; considered a variant of invasive Squamous Cell Carcinoma (SCC).

• Etiology: Sunlight (UV), chemical carcinogens (pitch and tar), trauma, HPV (types $9, 11, 13, 16, 18, 24, 25, 33, 37, 57$), and genetic factors ($8q, 1p, 9q$ gains; $3p, 9p, 19p, 19q$ deletions).

• Clinical Stages: (i) Proliferative, (ii) Mature, and (iii) Involutional/Resolving.

• Clinical Features:

  • Firm, round papule progressing to a dome-shaped nodule with a central crateriform ulceration or keratin plug.

  • Size: $1.0-1.5\,cm$ diameter.

  • Solitary lesions common on sun-exposed areas (face, neck, dorsum of hands).

• Ghadially Classification:

  • Type I: Bud-shaped (upper follicular origin).

  • Type II: Dome-shaped.

  • Type III: Berry-shaped (lower follicular origin).

• Histology:

  • Hyperplastic squamous epithelium with central keratin plugging.

  • Leading margin may look invasive, mimicking SCC.

  • Characteristic Margin: Normal adjacent epithelium is elevated toward the center of the crater with an abrupt change to hyperplastic epithelium.

  • SCC KA-type: Term for Classic KA with atypical mitotic figures and hyperchromatic nuclei.

• Management: Surgical excision. While spontaneous regression is possible (leaving a scar), it is not guaranteed.

Potentially Malignant Disorders (OPMDs)

Evolution of Terminology

• WHO 1978: Distinguished between "precancerous lesion" (morphologically altered tissue) and "precancerous condition" (generalized state).

• WHO 2005: Recommended the term "Potentially Malignant Disorder" (OPMD).

• WHO 2021 Definition: Any oral mucosal abnormality associated with a statistically increased risk of developing oral cancer.

• PPOEL: Potentially Premalignant Oral Epithelial Lesions—a broad term for histologic and clinical lesions with malignant potential.

Pathologic and Genetic Staging of OPMDs

• Zhang and Rosin Model: Categorizes risk based on Pathology ($P$) and Genetic ($G$) indices.

  • $P_1$: No or mild dysplasia.

  • $P_2$: Moderate dysplasia.

  • $P_3$: Severe dysplasia/CIS.

  • $G_1, G_2, G_3$: Low, intermediate, and high genetic risk (based on DNA ploidy).

• Risk Categorization:

  • Stage 1 (Lowest): $P_1 + G_1$.

  • Stage 2: $P_2$ or $G_2$ patterns.

  • Stage 3 (Highest): Severe dysplasia or high-risk genotype (e.g., $P_1 + G_3$).

• DNA Ploidy progression risk:

  • Diploid: $3\%$

  • Tetraploid: $60\%$

  • Aneuploid: $84\%$

Leukoplakia (White Patch)

Definition and Diagnostics

• Clinical Definition: "A white patch or plaque that cannot be characterized, clinically, or pathologically as any other disease" (WHO 1978). It is a diagnosis of exclusion.

• Clinical Requirements: Must not be scrapable; color does not disappear on stretching.

• Preleukoplakia: Grayish-white area with indistinct borders blending into normal mucosa.

Epidemiology and Classification

• Global Prevalence: $1.39\%$.

• Malignant Transformation Rate (MTR): Ranges from $3.54\%$ to $9.70\%$ (Average: $7.20\%$).

• Indian Context: Prevalence as high as $86.7\%$ in Bihar; highest among combined smoking and chewing habits ($6.0$ per $1000$).

• Clinical Types:

  • Homogeneous: Uniformly flat and thin, shallow cracks.

  • Nonhomogeneous: Includes Speckled (erythroleukoplakia), Nodular, and Verrucous (exophytic).

Etiology of Leukoplakia

• Tobacco: Strong dose-response relationship.

• Alcohol: Synergistic effect with other irritants.

• Microbiology:

  • Candida albicans: Found in $10\%$ of cases (Chronic Hyperplastic Candidiasis). Dysplasia is $4$ to $5$ times more frequent in candidal leukoplakia.

  • HPV (types $16, 18$): Associated with exophytic verrucous types.

• Nutritional Factors: Decreased serum Vitamin $A, B_{12}, C, \beta$-carotene, and folic acid.

Proliferative Verrucous Leukoplakia (PVL)

• Nature: Aggressive, multifocal, idiopathic form of leukoplakia with a high MTR ($49.5\%$).

• Clinical Course: At least $5$ years of evolution; initially focal, becoming widespread and warty.

• Demographics: More common in females (>60 years) and nonsmokers.

• Histologic Spectrum:

  1. Corrugated ortho(para)hyperkeratotic lesion.

  2. Bulky hyperkeratotic epithelial proliferation.

  3. Barnaculate Carcinoma: Cumbrous epithelium with a "stuck-on" appearance.

Epithelial Dysplasia and Architectural/Cytological Features

Architectural Features (WHO 2022)

• Irregular stratification: Loss of normal layering.

• Loss of Basal Polarity: Disordered stratification.

• Drop-shaped Rete Ridges: Denotes altered adherence and organization.

• Mitoses High in Epithelium: Mitosis in the prickle cell layer.

• Basal Cell Nesting: Clonal basal cells growing downward.

• Keratin Pearls: Found within rete ridges deep in the tissue.

Cytological Features (WHO 2022)

• Anisocytosis and Pleomorphism: Variations in cell size and shape.

• Nuclear Changes: Anisonucleosis (size), nuclear pleomorphism (shape), hyperchromasia (dark staining), increased nucleoli.

• $N:C$ Ratio: Increases from $1:4$ up to $1:1$.

• Single-cell Keratinization: Premature keratinization in lower layers.

• Atypical Mitoses: Tripolar or star-shaped forms.

Grading of Dysplasia

• Mild (Grade 1): Proliferation limited to the lower third of the epithelium.

• Moderate (Grade 2): Proliferation extends into the middle third; bulbous rete pegs.

• Severe (Grade 3): Proliferation reaches the upper third; prominent pleomorphism; "Carcinoma in situ" is used synonymously with this grade.

• Malignant Potential: Overall rate is $5\%-18\%$. Annual MTR for mild is $1.7\%$, for severe is $3.57\%$.

Oral Submucous Fibrosis (OSF)

Etiology and Pathogenesis

• Primary Factor: Habitual chewing of Areca Nut (Betel nut).

• Alkaloids: Arecoline, guvacine, arecaidine, and guvacoline. Arecoline is the most potent, promoting collagen synthesis and DNA alkylation.

• Mechanism:

  • Stimulation of fibroblast proliferation.

  • Decreased collagenase secretion.

  • Upregulation of Lysyl Oxidase (copper-dependent enzyme) which increases collagen cross-linkage.

  • Toxic levels of copper in areca nut stimulate angiogenesis (VEGF, TNF-$\alpha$, IL-$1$).

• Genetics: Associated with HLA-$A_{10}, B_7$, and $DR_3$.

Clinical Features of OSF

• Prodromal Signs: Burning sensation (spicy food), vesicles on palate, ulcerations, excessive salivation, dryness (xerostomia).

• Advanced Features:

  • Blanched, opaque mucosa with white fibrous bands (vertical in buccal mucosa).

  • Uvula Patterns: Deviated, inverted, hockey-stick, or bud-like shape.

  • Restriction: Difficulty opening mouth (trismus), inability to whistle/blow candle, swallowing difficulty, nasal voice.

  • Sunken checks and loss of nasolabial fold.

Histology

• Four Stages: Very early, early, moderately advanced, and advanced.

• Hallmarks: Subepithelial hyalinization (cross-linked collagen), avascularity, and secondary epithelial atrophy.

• MTR: $5.2\%$. Areca nut is a Group $1$ carcinogen (IARC).

Malignant Neoplasms: Basal Cell Carcinoma (BCC)

• Nature: Most common human malignancy; rare in oral cavity (only occurs via skin invasion).

• Etiology: UV radiation ($290 \times 320\text{ nm}$ sunburn rays) with a $20 \times 50$ year latency.

• Genetics: Mutations in $p53$ ($17p$) and $PTCH$ ($9q22.3$).

• Subtypes:

  • Nodular: Most common; pearly papule with telangiectasia.

  • Pigmented: Mimics melanoma.

  • Superficial: Scaly patches, often on the trunk.

  • Morpheaform/Sclerosing: Sclerotic scar-like plaques; high recurrence risk.

  • Pinkus Tumor (Fibroepithelial BCC): Soft papule on the lower back.

• Histology: Nests of basaloid cells with peripheral palisading and retraction artifact (clefting between nests and stroma).

Oral Squamous Cell Carcinoma (OSCC)

Epidemiology

• Global: $16^{\text{th}}$ most common cancer; >90\% of oral cancers.

• South Asia: High incidence due to betel quid; forms $45\%$ of all cancers in India.

• Mortality: Overall $5$-year survival is $63\%$. Lowest for lip ($0.04$/$100,000$), highest for tongue ($0.7$/$100,000$).

Genetic Basis of Oral Cancer

• EGF Pathway: Mutation in oncogenes (e.g., $ras$) sends a continuous growth signal via the kinase cascade (Raf, MEK, MAPK, c-myc).

• p53 Tumor Suppressor: Normal $p53$ stimulates $p21$ (CDK inhibitor) to block phosphorylation of $pRb$, stopping the release of E2F transcription factors.

• Apoptosis Pathway: $p53$ stimulates Bax, which blocks bcl-2, allowing Caspase 3 to proceed with cell death.

• Mutations: Mutation in $p53$ is found in up to $80\%$ of oral cancers.

Clinical Staging (TNM 8th Edition)

• T (Tumor):

  • $T_1$: $\leq 2\,cm, \text{DOI} \leq 5\,mm$.

  • $T_2$: \leq 2\,cm, \text{DOI} > 5\,mm \leq 10\,mm OR > 2\,cm, \leq 4\,cm, \text{DOI} \leq 10\,mm.

  • $T_3$: > 4\,cm OR any tumor with \text{DOI} > 10\,mm.

  • $T_4$: Invades deep structures (bone, sinus, skin).

• N (Node):

  • $N_1$: Single ipsilateral node $\leq 3\,cm$.

  • $N_2$: $3 \times 6\,cm$ or multiple nodes.

  • $N_3$: Node > 6\,cm.

  • ENE: Extranodal extension (classified as positive or negative).

• M (Metastasis): $M_0$ (None), $M_1$ (Distant).

Variants of Squamous Cell Carcinoma

• Verrucous Carcinoma (Ackerman Tumor): Slow-growing, exophytic, warty growth associated with tobacco chewing. Histology shows parakeratin plugging and broad bulbous rete ridges with an intact basement membrane.

• Spindle Cell Carcinoma (Lane Tumor): Rare, aggressive, biphasic tumor with epithelial and mesenchymal components (epithelial-mesenchymal transition).

• Basaloid SCC: Highly aggressive, lobulated sheets of basaloid cells with central necrosis and hyalinized stroma.

• Carcinoma Cuniculatum: "Rabbit burrow" pattern of keratin-filled crypts extending into bone.

• Adenoid SCC: Pseudoglandular appearance due to acantholysis.

• Lymphoepithelioma: Occurs in nasopharynx; associated with EBV. Cells show syncytial pattern and large nucleoli.

Malignant Melanoma of the Oral Cavity

• Epidemiology: Rare ($1.6\%$ of all melanomas), but more common in Japanese populations.

• ABCDE Rule: Asymmetry, Border irregularity, Color irregularity, Diameter > 6\,mm, Elevation.

• Clinical Features: Predilection for palate and maxillary gingiva. May show a radial growth phase (radial spread) before the vertical growth phase (invasion and metastasis).

• Survival: Dismal $5$-year survival rate of $7\%$.

• Diagnostics: Immunohistochemistry markers include S-100, HMB45, Melan-A, and Vimentin.

Metastatic Carcinomas

• Frequency: Less than $1\%$ of all oral tumors.

• Primary Source: Lung and Kidney (men); Breast and Thyroid (women).

• Common Sites: Jaws ($70\%$) and attached gingiva.

• Silent Primary: Cases where the primary tumor cannot be identified despite metastatic proof.

• Symptoms: Pain, swelling, and ill-defined radiolucency in the jaws.