**9. Clinical subtypes of oral lichenoid reactions**

(a) (b)

(a) (b)

**Figure 4.** a) Ulcerative (erosive) OLP (dorsal tongue); b) Ulcerative (erosive) OLP (buccal mucosa)

**Figure 5.** a) Desquamative gingivitis; b) Desquamative gingivitis with plaque form of OLP of central lower lip

**Figure 6.** OLP of the hard palate

158 Skin Biopsy - Diagnosis and Treatment

Oral lichenoid reactions encompass several clinical entities. [33-36]

**Oral Lichen Planus (OLP):** in which patients present with oral lichenoid lesions not readily attributable to any defined cause, that is to say "idiopathic" OLP. OLP represents one aspect of the spectrum of mucocutaneous lichen planus, which can affect potentially any mucosal surface, and/or the skin and its appendages.

**Oral Lichenoid Contact Lesions (OLCL):** due to allergic contact stomatitis (delayed immune mediated hypersensitivity) and seen in direct topographic relationship to dental restorative materials, most commonly amalgam (Figure 7). [36, 37]

**Figure 7.** Oral Lichen Contact Lesion (OCLC) – left buccal mucosa

**Oral Lichenoid Drug Reactions (OLDR:** in which oral and/or cutaneous lesions occur, temporally associated with the taking of certain medications, such as oral hypoglycaemic drugs, angiotensin converting enzyme (ACE) inhibitors, and non-steroidal anti-inflammatory agents (NSAIDS), but historically has been seen with the previous more wide-spread use of gold salts and penicillamine for the management of rheumatoid arthritis. [38]

**Oral Lichenoid Lesions of Graft versus Host Disease (OLL-GVHD):** in the setting of patients with acute, but predominantly, chronic graft versus host disease (cGVHD). [33]

Lichenoid responses or reactions ("lichenoid stomatitis") of the oral cavity may also be noted with other autoimmune or inflammatory diseases including connective tissue diseases and other immuno-bullous disorders. The cause(s) of the various oral lichenoid lesions, ranging from idiopathic oral lichen planus (OLP) to the "contact" lesion, is not understood, but all the lesions are characterized histologically by a typical "lichenoid tissue reaction" culminating in a common pathologic process, that of T-lymphocyte directed, immune mediated, damage to the oral epithelial basal cells. [1,2]

Essential Features (for histopathological diagnosis): ∙ Signs of "liquefaction degeneration" in the basal cell layer

∙ Normal epithelial maturation pattern (absence of epithelial dysplasia)

Separation of epithelium from lamina propria due to basal cell destruction

Non-Essential Histopathological Features that may also be seen: "Candle-dripping" or "saw-tooth"-like rete ridge conformation

tissue, consisting mainly of T-lymphocytes

Parakeratosis Civatte bodies

**diagnosis of OLP).**

∙ Blunt rete ridges

∙Epithelial Dysplasia/Atypia

→Atypical cytomorphology

→Prevalent dyskeratosis

→Disordered stratification ∙Heterogeneous inflammatory infiltrate

or perivascular infiltration

→Nuclear enlargement or hyperchromasia

Deep extension below superficial stroma

of the basal keratinocytes; c) Histopathology – civatte body

→Increased number of mitotic figures; aberrant mitosis

Heterogeneous inflammatory infiltrate with plasma cells and eosinophils

lesions. Oral Maxillofac Surg Clin North Am, 1994, 6, 445.) [3] (Figures 9a, 9b and 9c)

∙ Presence of well-defined bandlike zone of cellular infiltration confined to the superficial part of the connective

Oral Lichen Planus

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**Exclusionary Histopathological Features (the presence of which would preclude a definitive histopathological**

**Table 1.** Histopathological features of OLP (adapted from Eisenberg, E. Clinicopathologic patterns of oral lichenoid

**Figure 9.** a) Histopathology (low power) band-like inflammatory infiltrate; b) Histopathology – vacuolar degeneration

(a) (b) (c)

The diagnosis of OLP is usually made on clinical features alone. However, careful attention to the clinical history is essential, to ensure assessment, and if warranted, the appropriate management, of the extra-oral manifestations of lichen planus (Figures 8a and 8b). [1, 33-35]

**Figure 8.** a) LP of the skin; b) LP of the skin (close up)
