Oral cavity & oropharynx

• The sources of trauma / irritation that induce benign alveolar ridge keratosis include food impaction, chronic motion of an ill fitting denture or mucosal contact with an opposing, hypererupted or sharp tooth (Head Neck Pathol 2020;14:915)
• Morsicatio is a parafunctional habit that is more prevalent in those with excessive stress and mental illness (Dent J (Basel) 2019;7:15)
  • In addition to parafunctional habits, morsicatio can also be the result of abrasion from tooth brushing, orthodontic appliances and dentures (Head Neck Pathol 2021;15:572)

• No treatment is indicated for linea alba
• A biopsy may be performed on morsicatio buccarum to rule out hereditary conditions if suspected (e.g., white sponge nevus, hereditary benign intraepithelial dyskeratosis)
  • If the affected mucosa extends beyond the plane of occlusion, hereditary conditions are more likely
• Prior to performing a biopsy, an attempt should be made to identify a source of irritation; with removal of the irritant, resolution of the keratotic lesion should be observed within 2 weeks
  • Persistent lesions warrant biopsy (Dent J (Basel) 2019;7:15)

Contributed by Richard J. Vargo, D.M.D., M.B.A. and Elizabeth Ann Bilodeau, D.M.D., M.D., M.S.Ed.

• Linea alba
  • Parakeratosis overlying otherwise unremarkable stratified squamous epithelium
    • Intracellular edema of keratinocytes and mild chronic inflammation of the stroma may be seen in some cases
• Benign alveolar ridge keratosis
  • Parakeratosis or orthokeratosis and granulosis of the epithelium; the keratin layer may be shaggy and surface bacterial colonization may be observed (Head Neck Pathol 2020;14:915, Head Neck Pathol 2021;15:572)
    • Abrupt orthokeratotic / parakeratotic transitions should not be seen
  • Rete ridges are elongated, taper from superficial to deep and interconnect at their bases; vascular ectasia may be seen at the tips of the rete and stromal inflammation is scant or absent (Head Neck Pathol 2020;14:915)
  • No plasma pools in the superficial epithelium nor edema of keratinocytes are observed (Head Neck Pathol 2021;15:572)
• Morsicatio buccarum / labiorum and morsicatio linguarum
  • Acanthosis and parakeratosis with normal maturational changes of keratinocytes
    • Edema is present within keratinocytes; plasma pooling may also be noted in superficial epithelium (Head Neck Pathol 2021;15:572)
  • Surface parakeratin is ragged / shaggy in appearance; bacterial colonies and food debris may be noted within this ragged keratin
  • Stromal inflammatory infiltrate may or may not be present (Head Neck Pathol 2021;15:572)

Contributed by Joshua Seth Goldfaden, D.D.S.

Linea alba, morsicatio buccarum / labiorum and morsicatio linguarum


Benign alveolar ridge keratosis

• PAS is negative for fungal organisms
• EBER is negative in the spinous layer of lesions of morsicatio linguarum

• Materia alba:
  • Accumulation of desquamated epithelial cells with bacterial colonies and food debris, such as vegetable matter
    • Clinically, materia alba presents as a wipeable plaque that reveals normal, uninflamed underlying attached mucosa
• White sponge nevus:
  • Parakeratotic epithelium with acanthosis and spongiosis
  • Rete ridges are large and blunted
  • Epithelial cells exhibit compact eosinophilic peri and paranuclear condensation
• Leukoedema:
  • Parakeratinized, acanthotic epithelium with widened, elongated rete ridges
  • Spinous layer keratinocytes demonstrate hydropic degeneration (intracellular edema) with pyknotic nuclei
• Hereditary benign intraepithelial dyskeratosis:
  • Parakeratotic epithelium with acanthosis and keratinocyte discohesion in the superficial layers
  • Keratinocytes throughout epithelium exhibit dyskeratosis
    • The dyskeratotic process of this condition creates the illusion that keratinocytes appear to be engulfed by adjacent keratinocytes creating a "cell within a cell" appearance
• Smokeless tobacco keratosis:
  • Parakeratosis or orthokeratosis with acanthosis and church spires (chevroning)
  • Basket weaving / hydropic degeneration of the spinous layer epithelium may be seen
    • These epithelial cells may exhibit pyknotic nuclei
  • Mild chronic inflammation of the underlying connective tissue may be present
• Oral hairy leukoplakia:
  • EBER is positive in the spinous cell layer
  • Parakeratosis and ballooning degeneration of the spinous keratinocytes
  • Margination of chromatin (i.e., nuclear beading) of the spinous keratinocytes is observed; koilocytosis may also be noted
    • Both phenomena are cytopathic effects of an Epstein-Barr virus infection
  • Candidal organisms may be seen in the superficial epithelium, though an inflammatory response is typically absent
• Dysplasia (unifocal):
  • Expansion of basilar compartment and teardrop shaped rete ridges
  • Nuclear and cellular pleomorphism with increased N:C ratio
    • Nuclei may be hyperchromatic
  • Increased mitotic activity, single cell dyskeratosis and glassy appearance of some keratinocytes
• Proliferative verrucous leukoplakia (PVL):
  • Skip lesions consisting of sharply demarcated, alternating segments of orthokeratin and parakeratin
    • The keratin layer exhibits a verrucous / spiky architecture
  • Rete ridges may be bulbous, interconnect and exhibit downward pushing
    • This architectural dysplasia may obscure cytologic atypia
  • Epithelium may be atrophic in some instances
• Verrucous carcinoma:
  • Verrucous / papillary keratosis of the surface epithelium
    • Chevroning and deep keratin clefting are also noted
  • Broad, frond-like, bulbous rete ridges that demonstrate endophytic growth into the submucosa
    • Basement membrane remains intact
  • Keratinocytes are bland with minimal cytologic atypia
• Hyperplastic candidiasis:
  • Keratosis and acanthosis of the surface epithelium
  • Pseudohyphae are present in the stratum corneum and are oriented perpendicular to the epithelium
  • Pseudoepitheliomatous hyperplasia including elongated and bulbous rete ridges with a downward proliferating architecture; no cytologic atypia is observed
  • Underlying chronic inflammation with transmigratory neutrophils forming microabscesses in the stratum granulosum
• Lichen planus (plaque form):
  • Orthokeratosis or parakeratosis of the surface epithelium with Civatte bodies scattered throughout
  • Thickening of the basement membrane and hydropic degeneration of the basal cell layer
    • Hydropic degeneration of the basal cell layer may cause the rete ridges to appear saw toothed
  • Dense band of lymphohistiocytic inflammation immediately subjacent to the surface epithelium
• Dyskeratosis congenita:
  • Orthokeratosis and atrophy of the squamous epithelium
  • Over time, the lesions of this condition develop dysplastic changes and evolve into squamous cell carcinoma

A 55 year old man presents with a nonwipeable, ill defined white plaque of the right retromolar pad, distal to tooth #31. A biopsy of the lesion reveals stratified squamous epithelium with shaggy surface parakeratin, elongated, tapered rete ridges that coalesce and no cytologic atypia or stromal inflammation. Based on the clinical and histopathologic findings, what is the most appropriate diagnosis?

1. Benign alveolar ridge keratosis (BARK)
2. Dysplasia
3. Lichen planus
4. Materia alba

A. Benign alveolar ridge keratosis (BARK). A retromolar pad lesion with shaggy surface parakeratin, elongated, tapered rete ridges that coalesce and no stromal inflammation is consistent with benign alveolar ridge keratosis. Answer B is incorrect because dysplasia exhibits basal cell proliferation and teardrop shaped rete ridges; additionally, cellular and nuclear pleomorphism and increased mitotic activity are also characteristic of dysplasia. Answer C is incorrect because lichen planus exhibits saw toothed rete ridges, hydropic degeneration of the basal cell layer, Civatte bodies within the epithelium, thickening of the basement membrane and a tight band of lymphohistiocytic inflammation. Answer D is incorrect because materia alba is wipeable clinically and is histopathologically characterized by desquamated epithelial cells associated with bacterial colonies and food debris.

Comment Here

Reference: Frictional keratosis

A 22 year old female college student who is anxious about her upcoming final examinations presents with an ill defined white plaque of the lateral tongue. A biopsy is performed. Based on the photomicrograph, what is the most appropriate diagnosis?

1. Dysplasia
2. Lichen planus
3. Morsicatio linguarum
4. Oral hairy leukoplakia

C. Morsicatio linguarum. A lateral tongue lesion with ragged surface parakeratin, normal maturational changes of the epithelium, keratinocyte edema and surface bacterial colonization is consistent with morsicatio linguarum; additionally, a cause of trauma based on the patient’s social history is evident. Answer A is incorrect because dysplasia exhibits basal cell proliferation and teardrop shaped rete ridges; additionally, cellular and nuclear pleomorphism and increased mitotic activity are also characteristic of dysplasia. Answer B is incorrect because lichen planus exhibits saw toothed rete ridges, hydropic degeneration of the basal cell layer, Civatte bodies within the epithelium, thickening of the basement membrane and a tight band of lymphohistiocytic inflammation. Answer D is incorrect because oral hairy leukoplakia exhibits positive EBER in situ hybridization, ballooning degeneration of the spinous layer of epithelium and nuclear beading of the chromatin.

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Reference: Frictional keratosis

A 13 year old boy with orthodontic brackets and wires presents with bilateral, shagged, diffuse, white plaques of the buccal mucosae. An incisional biopsy reveals ragged surface parakeratin with surface bacterial colonization, normal maturational changes, superficial keratinocyte edema and minimal stromal inflammation. Based on the histopathologic findings, what is the most appropriate diagnosis?

1. Hereditary benign intraepithelial dyskeratosis
2. Leukoedema
3. Morsicatio buccarum
4. White sponge nevus

C. Morsicatio buccarum. Bilateral buccal mucosa lesion with ragged surface parakeratin, normal maturational changes of the epithelium, keratinocyte edema and surface bacterial colonization are consistent with morsicatio buccarum; additionally, a source of trauma (i.e., orthodontic appliances) is readily identifiable. Answer A is incorrect because hereditary benign intraepithelial dyskeratosis exhibits discohesion of the superficial layers of the epithelium and individual keratinocyte dyskeratosis that may create a "cell within a cell" appearance of the epithelium. Answer B is incorrect because the histopathologic appearance of leukoedema consists of widened, elongated rete ridges and hydropic degeneration of the spinous layer with pyknotic nuclei. Answer D is incorrect because white sponge nevus exhibits spongiotic epithelium with large, blunted rete ridges and epithelial cells with peri and paranuclear eosinophilic condensation.

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Reference: Frictional keratosis