You’re Reading a Preview Become a Clinical Tree membership for Full access and enjoy Unlimited articles Become membership If you are a member. Log in here
Introduction Virtually any tumor can metastasize to the skin, but some do so more often than others. The identification of the primary site is not always easy, and this process is further complicated by the occurrence of primary adnexal tumors of the skin that mimic various metastases. Immunohistochemistry has assisted in the specific diagnosis of these tumors, but it should be remembered that the specificity of…
Introduction A renewed interest in vascular tumors was provoked by the emergence of AIDS-related Kaposi's sarcoma in the 1980s, and since then a number of new entities have been described. Although many of these are rare, they may produce diagnostic dilemmas, several having many features in common with Kaposi's sarcoma. The classification of the vascular tumors and ectasias is far from straightforward. First, there is difficulty…
Introduction Neural tumors are an important category of cutaneous tumors. Although the vast majority of them can be diagnosed without difficulty, there are cases that require distinction from other spindle cell tumors, including melanoma. Markers are still being sought that will allow a reliable distinction between neural tumors and spindle cell melanomas. Cutaneous neural tumors arise from, or differentiate toward, one or more elements of the…
Tumors of Smooth Muscle Smooth muscle is found in the skin in three distinct settings: the arrector pili muscles; the walls of blood vessels; and the specialized muscle of genital skin, which includes the scrotum (dartos muscle), vulva, and nipple (areolar smooth muscle). Each of these sources of smooth muscle can give rise to benign tumors, resulting in three categories of cutaneous leiomyoma: piloleiomyoma, leiomyoma of…
The role of subcutaneous fat and the consequences of its increase and decrease have received little attention in the dermatological literature until comparatively recently. There are two types of adipose tissue, white and brown, that have different roles in energy metabolism. Most tumors of fat are derived from white adipocytes, but the rare hibernoma is derived from brown adipose tissue. The lipoma is by far the…
Introduction Recent immunohistochemical findings have assisted in the histogenetic classification of many of the soft tissue tumors. However, because vimentin is positive in many tumors, it is of no value in the differential diagnosis of tumors discussed in this chapter. On the other hand, the “fibrohistiocytic” tumors are still largely enigmatic with respect to their histogenesis, and the diagnosis is largely dependent on hematoxylin and eosin…
Introduction The cutaneous appendages give rise to a bewildering number of neoplasms—more than 80 in a recent count. Various classifications have been proposed in the past. Previous classifications have required modification from time to time in light of the most recent ultrastructural and histochemical findings and the reporting of new morphological entities. Ackerman and colleagues systematically reclassified many of the traditional “eccrine” tumors into apocrine categories,…
Introduction The histopathological diagnosis of pigmented skin tumors is an important area of dermatopathology. Note that melanin pigment may also be present in skin tumors other than nevocellular nevi and melanomas. For instance, seborrheic keratoses, basal cell carcinomas, and, rarely, squamous cell carcinomas, adnexal tumors, schwannomas, and dermatofibrosarcoma protuberans may contain melanin. Furthermore, there is a group of dermatoses characterized by variable patterns of hyperpigmentation covering,…
Introduction Tumors of the epidermis are a histopathologically diverse group of entities that have in common a localized proliferation of keratinocytes resulting in a clinically discrete lesion. They may be divided into a number of categories, reflecting their different biological behaviors. These include hamartomas (epidermal nevi), reactive hyperplasias (pseudoepitheliomatous hyperplasia), and benign tumors (acanthomas), as well as premalignant, in situ, and invasive carcinomas. There is a…
Introduction The phylum Arthropoda, which accounts for approximately 75% of animal species, is one of the most important sources of human pathogens. As well as acting as vectors of bacteria, viruses, rickettsiae, chlamydiae, spirochetes, protozoa, and helminths, arthropods may also produce lesions at their portal of entry into the skin. Furthermore, immunological reactions to the parasite or its parts may result in more widely disseminated cutaneous…
Introduction Helminthic parasites are responsible for a number of important diseases of tropical countries, including schistosomiasis, caused by the trematode flukes; cysticercosis and sparganosis, resulting from the larvae of certain tapeworms (cestodes); and onchocerciasis, dirofilariasis, and larva migrans occurring as a consequence of nematode infestations. The most common helminth infection in the United States and western Europe—enterobiasis (pinworm)—produces no primary cutaneous pathological conditions, although changes in…
Introduction Cutaneous injuries from various forms of marine life are uncommon recreational and occupational hazards. Many of the species encountered have a specific geographical localization. In most instances, a localized urticarial and inflammatory lesion results at the point of injury, but this may be accompanied by a laceration if a sharp dorsal spine is involved. The death of the noted marine adventurer Steve Irwin (the “Crocodile…
Introduction The protozoa are single-celled organisms of great medical importance. There are six categories, covering several phyla; not all are of dermatopathological interest: Amebae Flagellates Coccidia Microsporidia Ciliates Sporozoa The amebae include the organisms that cause amebiasis and acanthamebiasis. The flagellates constitute an important group that includes the organisms for trypanosomiasis, leishmaniasis, trichomoniasis, and giardiasis. The coccidia include Toxoplasma gondii and Cryptosporidium parvum ; only toxoplasmosis…
Introduction Viral infections of the skin are of increasing clinical importance, particularly in patients who are immunocompromised. Viruses may reach the skin by direct inoculation, as in warts, milker's nodule, and orf, or by spread from other locations, as in herpes zoster. Many viral exanthems result from a generalized infection, with localization of the virus in the epidermis or dermis or in the endothelium of blood…
Introduction Fungal infections of the skin are an important category of cutaneous disease. Included in this chapter are the dermatophytes, which produce countless millions of skin infections each year, and the systemic and related mycoses, whose clinical importance usually pertains to their involvement of organs other than the skin. This category assumes life-threatening importance in immunosuppressed individuals, a significant group being those suffering from HIV Organ…
Introduction The order Spirochaetales has two genera of medical importance, Treponema and Borrelia . Spirochetes are one of the few bacterial groups for which classic morphological criteria and RNA sequence analyses agree in predicting the phylogenetic relationships among the various members of the order. Treponematoses The treponematoses are caused by infection with the spirochete Treponema pallidum and its various subspecies. They include the following: Syphilis Endemic…
Introduction Various bacteria form part of the normal resident flora of the skin. In the past, these organisms were regarded as symbiotic, but there is emerging evidence that these organisms may protect the host; as such, they are mutualistic rather than symbiotic. In certain circumstances, some of these bacteria may assume pathogenic importance. Other bacteria are present only in pathological circumstances. In this chapter, the following…
You’re Reading a Preview Become a Clinical Tree membership for Full access and enjoy Unlimited articles Become membership If you are a member. Log in here
Introduction Various physical agents, such as trauma, heat and cold, radiation, and light, may cause lesions in the skin. This is not an exhaustive account of all the reactions that can theoretically result from physical injuries because some are of little dermatopathological importance. Several entities produced by physical agents have been discussed in other chapters because they possess a distinctive histopathological pattern. For completeness, brief mention…