7 topics with concise reviews: definitions, key facts, and class questions.
This chapter is dedicated to the pathological anatomy of the skin, the largest human organ. Here we examine basic pathomorphology, including fundamental tissue reactions (hyperkeratosis, acanthosis, spongiosis) as well as structural changes in the epidermis and dermis.
This section covers key groups of nosologies. You will study the microscopic picture of inflammatory and infectious dermatoses, the mechanisms of acantholysis in bullous lesions, and the principles of morphological diagnosis of neoplasms, specifically epithelial skin tumors and melanocytic nevi.
During practical classes and exams, traditional emphasis is placed on oncopathology. Instructors will invariably ask about the differential diagnosis of various nevi, as well as the histological criteria for basal cell carcinoma and squamous cell carcinoma. In the non-oncological section, you are most often required to explain the morphological differences between pemphigus vulgaris and bullous pemphigoid. Study the microscopic specimens carefully—this is the foundation for successfully passing.
What is the difference in the localization of sweat gland ducts?
The ducts of eccrine glands pierce the epidermis and open directly onto the skin surface, whereas the ducts of apocrine glands empty into the hair follicle.
What are Wickham's striae?
This is a characteristic reticular pattern on the surface of papules in lichen planus, formed due to uneven thickening of the granular layer of the epidermis.
What is the main histological difference between herpes zoster and herpes simplex?
The pathomorphology is similar, but in herpes zoster the changes are significantly more pronounced: there is more massive dermal edema, involvement of peripheral nerves and blood vessels, and the development of thrombosis and hemorrhages.
Why do clefts appear in basal cell carcinoma histological slides?
These are artifactual clefts arising during histological processing. They form due to weakness and insufficiency of hemidesmosomes, leading to detachment of the tumor tissue from the surrounding stroma.
Which histological sign indicates the degree of differentiation of squamous cell carcinoma?
The degree of hyperkeratosis, i.e., the number and maturity of "keratin pearls" in the center of the tumor cell nests.
What is the "shoulder" sign in the histological examination of a nevus?
This is a sign of a dysplastic nevus, in which the epidermal component exceeds the dermal one in extent and extends peripherally beyond it by at least 3 epidermal ridges.
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