Introduction

Pathology of the oral cavity affects the following structures: (1) the mucosa, (2) the salivary glands, and (3) the jaw bones. Lesions may extend into the oropharynx, sinuses, and the skin. As such, the scope of practice of oral and maxillofacial pathology overlaps with otorhinolaryngologic pathology, dermatopathology, and bone pathology. The oral cavity is also the primary site for the development of lymphomas and many soft tissue tumors, and is also sometimes the location of metastatic tumors. This atlas focuses on pathology that is frequently seen in the oral cavity.

Unlike the skin, mucosal lesions in the oral cavity may manifest only in a limited number of ways—erythematous/erosive (from epithelial atrophy, vascular ectasia, and inflammation), white (from keratosis or underlying fibrosis), yellow/ulcerative (from fibrinous exudate), vesiculobullous (often erosive), pigmented, papillary, diffuse or nodular swelling, and mass. It is important for the pathologist to be familiar with clinical presentations of mucosal disease for accurate diagnosis. Clinical images (even those taken with a smartphone) or radiographic images are often indispensable for the diagnosis of mucosal lesions and osseous pathology, respectively.

Anatomy

The oral mucosa varies clinically and histologically from site to site, and is divided into keratinized and nonkeratinized mucosa ( Fig. 1.1 ). Specific oral conditions correlate with oral anatomy: for example, recurrent aphthous ulcers occur primarily on the nonkeratinized mucosa, whereas recrudescent herpes simplex virus infections occur almost exclusively on the keratinized mucosa (such as the hard palatal mucosa and keratinized gingiva) in immune-competent patients. The tongue dorsum (with the thickest epithelium in the oral cavity) but not ventrum (with thin epithelium) is specialized for gustatory, masticatory, and deglutition functions. Filiform papillae cover the entire surface of the dorsum. Taste buds are present within fungiform (on dorsum), circumvallate (8 to 14 on the posterior dorsum), and foliate (posterior lateral tongue) papillae but not within filiform papillae ( Fig. 1.2 ). The lingual tonsil extends across the base of the tongue and may extend into the foliate papillae. The oral mucosa contains no submucosa per se because there is no muscularis mucosa or any other consistently recognizable histologic landmark that separates mucosa from submucosa. As such, the terms papillary (between rete ridges), superficial , and deep lamina propria are preferable to submucosa . In general, the epithelium of the oral cavity is much thicker than that of the skin ( Table 1.1 ; Figs. 1.3–1.9 ). The keratinocytes are generally well glycogenated and may exhibit perinuclear halos; these should not be misdiagnosed as koilocytes. Muscle is present fairly superficially on the tongue and slightly deeper on the buccal and lip mucosa. Minor salivary glands are predominantly mucous, although serous acini and demilunes are frequently seen ( Fig. 1.10 ); they are present everywhere in the mouth except on the keratinized gingiva (also known as “attached” gingiva because of its “attachment” to the periosteum and bone). Serous salivary glands with a smaller mucous component are frequently encountered on the anterior ventral tongue (glands of Blandin-Nuhn) and posterior lateral and dorsal tongue (glands of von Ebner), sometimes invested in muscle.

FIG 1.1
Gingival mucosa showing marginal and attached (keratinized) gingiva and nonattached (nonkeratinized) gingiva.

FIG 1.2
(A) Tongue showing filiform papillae (generalized “fur”) and circumvallate papillae (arrow) , as well as epiglottis behind the uvula. (B) Tongue with inflamed fungiform papillae (small red papules).

TABLE 1.1
Histology of Oral Mucosa at Different Sites
Site Appearance
  • Nonkeratinized mucosa (thick)

    • Buccal mucosa

    • Labial mucosa

  • Buccal and labial mucosa are contiguous and similar (see Fig. 1.3 )

    • Epithelium 15–25 cells thick

    • Broad, tapered rete ridges

    • Loose fibrovascular tissue in the lamina propria or corium; muscle at the base

  • Nonkeratinized mucosa (intermediate)

    • Nonattached gingiva/alveolar mucosa

  • Nonattached gingiva/alveolar mucosa

    • Intermediate in thickness between buccal mucosa and floor of mouth

  • Nonkeratinized mucosa (thin)

    • Floor of mouth

    • Ventral tongue

    • Soft palate/fauces

  • Floor of mouth and ventral tongue are contiguous and similar to soft palate (see Fig. 1.4 )

    • Epithelium 10–15 cells thick

    • Short or poorly formed rete ridges

    • Ventral tongue in the anterior and posterior often contains serous salivary glands (glands of Blandin-Nuhn and von Ebner, respectively) (see Fig. 1.5 )

  • Keratinized mucosa

    • Hard palatal mucosa

    • Attached gingiva

  • Hard palatal mucosa and attached gingiva are similar (see Fig. 1.6 )

    • Thin layer of orthokeratin with thin granular layer

    • Epithelium 15–25 cells thick

    • Gingiva has more tapered, slender rete ridges; may see odontogenic rests of Serres (see Fig. 1.7 )

    • Dense fibrous tissue and periosteum at the base

    • Hard palatal mucosa often has fatty tissue investing neurovascular bundles and minor salivary glands

  • Keratinized and specialized mucosa

    • Tongue dorsum

  • Moderate-to-thick layer of parakeratin

    • Filiform papillae are keratin spires surrounded by bacterial colonies (see Fig. 1.8 )

    • Epithelium 20–30 cells thick

    • Fungiform, circumvallate, and foliate papillae are fibrovascular polypoid structures containing taste buds (see Fig. 1.9 ); subgemmal neurogenous plaque are usually present in the lamina propria

    • Posterior dorsum and lateral tongue contain lingual tonsils

    • Skeletal muscle is superficial

Oct 3, 2019 | Posted by in Oral and Maxillofacial Pathology | Comments Off on Introduction
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