Clinical Pathology of Nevi and Facial Malformations

Classification and Features of Nevi

Nevi are categorized into several types based on their clinical and histological characteristics:

• 1) Keratotic Nevi: Also known as white spongy nevus.
• 2) Vascular Nevi: Includes Hemangioma and Lymphangioma.
• 3) Pigmented Nevi: These are further subdivided into:

Pigmented Nevi Varieties

• A) Intradermal Nevus: Located in the connective tissue (CT). It presents as a papillomatous shape, often containing hair, and is less pigmented. Histopathology: Benign, non-encapsulated proliferation of nevus cells; lacks dendritic processes, has less cytoplasm, and contains less melanin.
• B) Junctional Nevus: Located at the dermal-epidermal junction. It is flat and black in color. Histopathology: Benign, non-encapsulated proliferation of nevus cells; lacks dendritic processes, shows junctional activity, and contains cytoplasm and melanin.
• C) Compound Nevus: Located at both the junction and within the connective tissue. It presents as an elevated papule and is brown in color. Histopathology: Benign, non-encapsulated proliferation of nevus cells; lacks dendritic processes, and contains cytoplasm and melanin.
• D) Blue Nevus: Commonly found on the hands, feet, and palate. It is macular or dome-shaped and appears blue due to the Tyndall effect. Histopathology: A collection of elongated, slender melanocytes with melanin granules located deep in the lamina propria.
• E) Spitz Nevus (Juvenile): Typically occurs in childhood as a pink papule. Histopathology: Shows junctional activity and the presence of Kamino bodies.
• F) Halo Nevus: Located on the skin of the trunk, characterized by a hypopigmented border. Histopathology: Contains chronic inflammatory cells and may regress without treatment.

Reactive and Benign Lesions

Pyogenic Granuloma: A reactive lesion and a double misnomer, often associated with pregnancy. It is primarily found on the gingiva. Histopathology: Small spaces filled with blood and lined by endothelial cells, mixed inflammatory cells, and an ulcerated surface. It may eventually mature into an irritational fibroma.

Chondroma: A benign tumor of the cartilage. Histopathology: Encapsulated hyaline cartilage with cells containing one nucleus and a fibrous stroma. X-ray: Presents as an irregular radiolucency (RL) with mottled radiopacity (RO).

Developmental Disturbances of the Face

• 1) Oblique Facial Cleft: Caused by the failure of fusion between the maxillary and lateral nasal processes. It runs from the inner canthus of the eye to the ala of the nose.
• 2) Transverse Facial Cleft: Caused by the failure of fusion between the maxillary and mandibular processes. It runs from the angle of the mouth to the ear.
• 3) Macrostomia and Microstomia: Macrostomia results from the failure of fusion between the maxillary and mandibular processes, while microstomia is caused by their excessive fusion.
• 4) Facial Hemihypertrophy: A congenital malformation affecting one half of the face. Etiology: Vascular or genetic. Clinical features: Enlargement of the teeth, tongue, and jaw, often leading to the early shedding and eruption of teeth.

Developmental Disturbances of the Lip

• 1) Cheilitis Glandularis: An inflammatory condition of the lower lip involving exposed minor salivary glands.
• 2) Cheilitis Granulomatosa: A firm, non-tender swelling of the upper lip associated with Melkersson-Rosenthal syndrome. Histopathology: Non-specific granulation tissue, chronic inflammatory cells, and epithelioid cells.
• 3) Congenital Lip Pit: A shallow depression on the vermillion border. Commissural lip pits occur at the corners of the mouth due to the failure of fusion between the maxillary and mandibular processes.
• 4) Cleft Lip (Pre-alveolar): Etiology: Genetic or congenital.
  • A) Lower Lip: Median cleft lip caused by the failure of fusion of the two mandibular processes.
  • B) Upper Lip: Can be unilateral, bilateral, or mixed, caused by issues between the median nasal and maxillary processes.