Conjunctival papilloma.

Conjunctival papillomas are some of the most common tumors of the conjunctiva and are well-described in ophthalmology textbooks. However, they have not be well-recognized by the dermatologic community. These lesions may be encountered by the dermatologist during a full skin examination or they may be the presenting concern of a patient.

Histopathology of alopecia areata, acute and chronic: Why is it important to the clinician?

Alopecia areata (AA) is often easy to diagnose but a scalp biopsy for horizontal sectioning is routine in this research clinic. The characteristic histological feature of AA is the peribulbar and intrabulbar mononuclear cell infiltrate, which occurs in the acute stage of the disease but may be absent in biopsies taken at a later stage. AA evolves through acute, subacute, chronic, and recovery phases. Increased numbers of terminal catagen and telogen hairs are found in the acute and perhaps subacute stages with increased numbers of miniaturized, vellus-like hairs in the subacute and chronic stages. Thus, it is important for clinicians and pathologists to recognize the different phases of AA, so that in the absence of the classic findings of a peribulbar lymphocytic infiltrate, a diagnosis of AA can still confidently be made.

Tropical dermatology: Tropical diseases caused by protozoa.

UNLABELLED: Protozoan infections are very common among tropical countries and have an important impact on public health. Leishmaniasis is the most widely disseminated protozoan infection in the world, while the trypanosomiases are widespread in both Africa and South America. Amebiasis, a less common protozoal infection, is a cause of significant morbidity in some regions. Toxoplasmosis and pneumocystosis (formerly thought to be caused by a protozoan) are worldwide parasitic infections with a very high incidence in immunocompromised patients but are not restricted to them. In the past, most protozoan infections were restricted to specific geographic areas and natural reservoirs. There are cases in which people from other regions may have come in contact with these pathogens. A common situation involves an accidental contamination of a traveler, tourist, soldier, or worker that has contact with a reservoir that contains the infection. Protozoan infections can be transmitted by arthropods, such as sandflies in the case of leishmaniasis or bugs in the case of trypanosomiases. Vertebrates also serve as vectors as in the case of toxoplasmosis and its transmission by domestic cats. The recognition of the clinical symptoms and the dermatologic findings of these diseases, and a knowledge of the geographic distribution of the pathogen, can be critical in making the diagnosis of a protozoan infection. LEARNING OBJECTIVES: After completing this learning activity, participants should be able to recognize the significance of protozoan infections worldwide, identify the dermatologic manifestations of protozoan infections, and select the best treatment for the patient with a protozoan infection.

Eccrine porocarcinoma.

Eccrine porocarcinoma (EPC) is a rare cutaneous neoplasm that grows slowly over a long period of time but often experiences an accelerated growth phase. This malignant tumor may arise denovo or evolve from a pre-existing benign eccrine poroma. Histologic evaluation demonstrates anaplastic cells involving the epidermis and infiltrating the dermis. Metastasis to regional lymph nodes distally occurs in a significant number of cases. Treatment modalities have included standard excision, Mohs micrographic surgery (MMS), chemotherapy, and radiation therapy. Recently sentinel lymph node biopsy has begun to be investigated as a staging tool. The literature on EPC is reviewed with attention paid to which of the various therapeutic options offers a clear advantage over the others. MMS affords the greatest likelihood of clear margins and cure in absence of regional and distant metastases.

Melanoma in situ with epidermal effacement: a compelling adjunctive finding.

Since many studies have shown the discordant diagnoses of melanocytic lesions among pathologists despite the existence of an established histologic criteria, we sought to refine the histologic criteria by finding an additional reliable and reproducible objective histopathologic feature to aid in the diagnosis of melanoma in situ. We performed a retrospective analysis of 100 cases histologically diagnosed as melanoma in situ and compared them to a study control group consisting of junctional benign melanocytic nevi. The epidermis of all the melanocytic lesions was examined for epidermal effacement. Examination of the epidermis in the study group revealed an absence of epidermal effacement in only 7 (10%) cases, whereas 93 (93%) cases showed an absence of rete ridges in some foci, making this an overwhelming majority finding in the cases examined. These results serve as a compelling adjunctive finding that can be used to increase the histologic diagnostic accuracy of melanoma in situ.

Office diagnosis of hair shaft defects.

Hair shaft abnormalities are fascinating and can provide a diagnostic challenge. Current knowledge of structural changes in hair has been amplified by scanning and transmission electron microscopy (SEM and TEM). Dermatologists using the light microscope and polarization in the office can diagnose the great majority of hair shaft defects. A number of these defects are illustrated here.

The platelet-activating factor receptor activates the extracellular signal-regulated kinase mitogen-activated protein kinase and induces proliferation of epidermal cells through an epidermal growth factor-receptor-dependent pathway.

Platelet-activating factor (PAF) is a lipid mediator that has been implicated in a variety of keratinocyte functions. Keratinocytes express the specific receptor for PAF (PAF-R), a seven-transmembrane G-protein-coupled receptor. Although PAF-R-dependent stimulation of numerous signal transduction pathways has been shown in a variety of cell types, to date there has been no analysis of PAF-R signal transduction in human epidermal cells. There is also contradictory evidence that PAF acts as either a suppressor or activator of keratinocyte proliferation. Using a model system created by retroviral-mediated transduction of the PAF-R into the PAF-R-negative epidermal cell line KB, we now demonstrate that the activation of the epidermal PAF-R results in the activation of both the extracellular signal-regulated kinase (ERK) and p38, but not the jun N-terminal kinase mitogen-activated protein (MAP) kinase pathways. Additionally, we show that the activation of the PAF-R stimulates the replication of epidermal cells. The activation of the ERK signal transduction pathway, as well as the PAF-dependent increase in cell proliferation, was dependent on the transactivation of the epidermal growth factor receptor (EGF-R). PAF-R-induced transactivation of the EGF-R was blocked by pharmacologic inhibitors of matrix metalloproteinases, of heparin-binding epidermal growth factor (HB-EGF), and specific inhibitors of the EGF-R tyrosine kinase. Activation of p38 MAP kinase by the PAF-R was not dependent on EGF-R activation and represents a distinct pathway of PAF-R-mediated signal transduction. In summary, these studies provide a mechanism whereby the PAF-R can exert proliferative effects through the activation of the EGF-R.