Histopathology

The epithelium of all precursor lesions is generally thickened. However, in a minority of cases patchy atrophy, thinning of the viable cellular layers, may be present. By definition there is no evidence of invasion. The magnitude of surface kera-tinization is of no importance. Allocation to categories within each of the classifications requires consideration firstly of architectural features and then of cytology.

1. Hyperplasia

Definition: Hyperplasia describes increased cell numbers. This may be in the spinous layer (acanthosis) and/or in the basal/parabasal cell layers (progenitor compartment), termed basal cell hyperplasia.

The architecture shows regular stratification and there is no cellular atypia.

Fig. 3.40 Mild dysplasia (basal-parabasal cell hyperplasia, SIN1). A Note the increased number of basal-parabasal cells with hyperchromatic, uniform nuclei, perpendicularly oriented to the basement membrane. The upper part of the epithelium shows a regular spinous layer and thin parakeratotic layer on the surface. B Increased number of uniform, slightly enlarged basal and parabasal cells, perpendicularly oriented to the basement membrane. Increased number of regular mitoses are evident. At the right corner (lower half) the epithelial cells show minimal cytologic atypia. The upper half of the epithelium is composed of regular spinous cells, which become flattened toward the surface. A thin parakeratotic layer is present on the surface.

Fig. 3.40 Mild dysplasia (basal-parabasal cell hyperplasia, SIN1). A Note the increased number of basal-parabasal cells with hyperchromatic, uniform nuclei, perpendicularly oriented to the basement membrane. The upper part of the epithelium shows a regular spinous layer and thin parakeratotic layer on the surface. B Increased number of uniform, slightly enlarged basal and parabasal cells, perpendicularly oriented to the basement membrane. Increased number of regular mitoses are evident. At the right corner (lower half) the epithelial cells show minimal cytologic atypia. The upper half of the epithelium is composed of regular spinous cells, which become flattened toward the surface. A thin parakeratotic layer is present on the surface.

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Fig. 3.41 Moderate dysplasia (atypical hyperplasia, SIN 2). A The epithelium is slightly thickened. More than half of the epithelium is occupied by increased number of slightly to moderately polymorphic epithelial cells with hyperchromatic nuclei and increased mitotic activity. The upper third shows spinous cell differentiation; prominent granular and keratotic layer is evident on the surface. B Hyperplastic epithelium with increased number of slightly to moderately polymorphic epithelial cells extending up to two thirds of the epithelium. A thin parakeratotic and keratotic layer is present on the surface.

2. Dysplasia (intraepithelial neoplasia, atypical epithelial hyperplasia potentially malignant lesions)

Definition: When architectural disturbance is accompanied by cytologic atypia the term dysplasia applies. There is a challenge in the recognition of the earliest manifestations of dysplasia, and no single combination of the above features allows for consistent distinction between hyperplasia and the earliest stages of dysplasia as well as in attempting to rigidly divide the spectrum of dys-plasias into mild, moderate and severe categories.

Mild dysplasia

In general architectural disturbance limited to the lower third of the epithelium accompanied by cytological atypia define the minimum criteria of dysplasia.

Moderate dysplasia

Architectural disturbance extending into the middle third of the epithelium is the initial criterion for recognizing this category. However, consideration of the degree of cytologic atypia may require upgrading.

Severe dysplasia

Recognition of severe dysplasia starts with greater than two thirds of the epithelium showing architectural disturbance with associated cytologic atypia. However, as noted in the previous paragraph, architectural disturbance extending into the middle third of the epithelium with sufficient cytologic atypia may be upgraded from moderate to severe dys-plasia.

Carcinoma in-situ

The theoretical concept of carcinoma in-situ is that malignant transformation has occurred but invasion is not present. It is not always possible to recognize this morphologically. The following is recommended for the diagnosis of carcinoma in-situ: full thickness or almost full thickness architectural abnormalities in the viable cellular layers accompanied by pronounced cytologic atypia. Atypical mitotic figures and abnormal superficial mitoses are commonly seen in carcinoma in-situ.

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