Path lab exam notes I

Basal cell carcinoma -- arises from basal cell layer of epidermis; multifocal nests of intensely basophilic cells, palisading at the borders; invasion into the dermis -- hence malignant. Like locations: upper lip, inner canthus of the eye.

Psoriasis -- red plaques with white scales; symmetric distribution, frequently on elbows and knees, scalp, genitalia, in general extensor surfaces (in contrast to eczema); acanthosis (thickening of the stratum spinosum), hyperkeratosis (thickening of stratum corneum), perikeratosis (retention of nuclei in stratum corneum); tall dermal papillae.

Herpes zoster -- intraepidermal blisters; at borders of blisters, can see eosinophilic intranuclear inclusions with clear border and then round rim of basophilic marginated chromatin; "dew drop on a rose petal" -- small blister on a red macule; Tzanck stain detects multinucleated epidermal giant cells.

Eczematous dermatitis -- spongiosus.

Melanoma -- brown melanin pigment

Squamous cell carcinoma -- Scaly to nodular lesions, often ulcerated; lower lip, dorsum of hand, or earlobe are common locations (contrast basal cell).

Acne -- hair follicle with keratin and sebum in dermis; foci of inflammation in adjacent wall.

Lupus -- lymphocytic infiltrates in dermis and dermal-epidermal junction; follicular plugging in epidermis; forehead, ear lesions, wolf rash

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Eosinophil -- bilobed nucleus, red granules (look like they have rods or long scrolls in them on EM).

Type II pneumocytes also have distinctive lamellar bodies.

Peritoneal inflammation -- opaque rather than glistening peritoneal surface, petechial hemorrhages,

Alveolar inflammation -- first pass is neutrophils, second pass is macrophages; foamy quality due to lipids in cell walls of phagocytosed bacteria. Macrophages are like a diagnosis of exclusion: not particularly distinctive -- renniform (kidney-shaped) nucleus (not lobulated like neutrophils), more cytoplasm and larger than neutrophils, not really any distinctive granules.

Plasma cell -- eccentric and clockface nucleus, perinuclear clear space; large cell like macrophage, but reddish purple (darker) cytoplasm due to large amount of RER.