Adnexal tumors or tumorous proliferations are generally classified according to two principles, (1) benign versus malignant and (2) line of differentiation, that is, which normal cutaneous structure the lesion most resembles (hair follicle, apocrine or eccrine gland, or sebaceous gland).…
Benign Tumors and Tumorous Proliferations of the Epidermis The lesions described herein include noninfectious pseudoepitheliomatous epidermal hyperplasia, benign acanthomas and keratoses, and epidermal nevi. Epidermal proliferations associated with warts or deep fungal infections are described in the chapter on infectious…
A cyst is a dilated, saclike cavity lined by various types of epithelia. In the vast majority of cases, cutaneous cysts are lined by one type of epithelium, most commonly stratified squamous epithelium. Infrequently, cutaneous cysts may have significant portions…
Non-neoplastic disorders of hair comprise mainly the alopecias and hair shaft abnormalities. In this chapter, only the alopecias are considered. Their diagnosis requires close clinicopathologic correlation. The hair shaft abnormalities are covered extensively in various textbooks and atlases, and readers…
This chapter describes key clinical and histologic features of relatively common or well-known non-neoplastic disorders of pigmentation. Café-Au-Lait Macules Clinical Findings Café-au-lait macules are very common. Solitary lesions are seen in approximately 10% to 20% of the adult population. They…
This chapter includes cutaneous substances that may accumulate in abnormal amounts, such as mucin, as well as material deposits usually not present in the skin, either produced endogenously (e.g., porphyrins) or introduced as a foreign substance (e.g., tattoo pigment). Deposits…
A blister is a fluid-filled space within or beneath the epidermis. Blisters may occur as a secondary event caused by factors such as infections (e.g., viral, bacterial), ischemia (e.g., vasculitis), burns, or inflammation leading to disruption of the dermal-epidermal junction…
Vasculitis is a histologic diagnosis defined as inflammatory cell infiltration and destruction of blood vessels. Vasculitis is generally classified as primary vasculitis (idiopathic e.g., cutaneous leukocytoclastic angiitis [CLA], granulomatosis with polyangiitis [GPA]); secondary vasculitis (a manifestation of connective tissue diseases…
Viral Infections Human Papilloma Virus Warts (Verrucae) The human papilloma virus (HPV) is the most prominent member of the papovaviruses group. There are more than 100 distinct HPV genotypes, some of which have oncogenic potential. Clinical Findings Different HPV strains…
This chapter reviews inflammatory diseases involving the subcutaneous fat tissue (panniculitis). Although panniculitis is typically centered on the subcutis, many forms of panniculitis are associated with internal organ involvement or represent a manifestation of an associated systemic disease. The focus…