Microphthalmia transcription factor immunohistochemistry: a useful diagnostic marker in the diagnosis and detection of cutaneous melanoma, sentinel lymph node metastases, and extracutaneous melanocytic neoplasms.

BACKGROUND: Melanoma is the most lethal form of skin cancer. Diagnosis of amelanotic melanoma and detection of micrometastases in sentinel lymph nodes pose diagnostic and therapeutic dilemmas for the dermatopathologist and clinician. OBJECTIVE: The purpose of this article is to determine the utility of immunohistochemistry using antibodies specific for microphthalmia in the identification of melanocytic lesions in the skin, eye, central nervous system, and sentinel lymph nodes. METHODS: Paraffin-embedded, formalin-fixed specimens of cutaneous melanoma, including amelanotic melanoma and lentigo maligna melanoma, were stained with antibodies specific for microphthalmia. In addition, paraffin sections of extracutaneous lesions, including sentinel lymph nodes, uveal melanoma, and central nervous system melanocytomas, were stained with the specific microphthalmia antibody. RESULTS: All cutaneous melanomas stained positively with microphthalmia, as did uveal melanomas and central nervous system melanocytomas. These findings confirm the melanocytic origin of melanocytomas and uveal melanomas and demonstrate that microphthalmia staining can be used to establish melanocytic origin of neoplasms. In addition, micrometastases were easily detected in sentinel lymph nodes. CONCLUSION: Microphthalmia transcription factor immunohistochemistry is a valuable tool in the identification of melanocytic lesions in numerous sites. Use of this stain may facilitate detection of micrometastases in sentinel lymph nodes.

Is monochromatic irradiation testing useful in the differentiation of drug-induced photosensitivity from chronic actinic dermatitis?

Chronic actinic dermatitis (CAD) is an uncommon, eczematous photosensitive eruption affecting predominantly elderly men and to which drug-induced photosensitivity may sometimes appear clinically identical. This retrospective study compares the monochromatic irradiation results in 11 patients with CAD and 14 patients with drug-induced photosensitivity, to assess whether such testing is useful in the differentiation of these two conditions. Thus, the action spectra of the drug photosensitivity patients were plotted and compared with those of 12 nonphotosensitive control patients: 10 patients were found to be photosensitive in the UVA range; the implicated drugs included quinine, sparfloxacin, amiodarone, doxycycline, mefenamic acid, nalidixic acid, fenbrufen, diclofenac, enalapril, diltiazem and prochlorperazine maleate. One patient on doxycycline was photosensitive in both the UVA and UVB ranges. The remaining three patients were not tested until after discontinuation of their drug and their light tests were then normal. In the CAD group, five patients were photosensitive in the UVA, UVB and visible light ranges and six were photosensitive in the UVA and UVB ranges. Comparison of the mean minimal erythema dose responses then demonstrated dissociation of the drug-induced from the CAD group in the UVB region; the result was statistically significant. This suggests that UVA-sensitivity dissociated from UVB-sensitivity is a relative indicator of drug-induced photosensitivity and monochromatic irradiation testing may therefore be helpful in the differentiation of these two disorders.

Screening of patients with iron overload to identify hemochromatosis and porphyria cutanea tarda.

OBJECTIVE: To assess the importance of iron overload as a risk factor for porphyria cutanea tarda (PCT). DESIGN: Prospective study during a 4-month period. SETTING: Departments of emergency care, gastroenterology, and dermatology in a tertiary referral center. PATIENTS: Patients were deemed eligible for inclusion in the study if serum ferritin levels were greater than 500 micrograms/L (normal range: females, < 125 micrograms/L; males, < 325 micrograms/L). MAIN OUTCOME MEASURES: Porphyrin excretion profiles were analyzed on all patients included in the study, where clinically relevant. A diagnosis of PCT was confirmed biochemically in all cases. The HLA typing was then performed on newly diagnosed cases of PCT. RESULTS: Of 4127 patients tested, 240 patients with an elevated serum ferritin level were identified, of whom 74 had an elevated serum ferritin level of more than 500 micrograms/L. Of the latter group, 17.5% had hemochromatosis and 6.7% had PCT. The incidence of PCT in the hemochromatosis group was 23%; HLA typing revealed the presence of at least 1 of the hemochromatosis markers. CONCLUSIONS: A high serum ferritin level in the absence of evident cause should prompt investigation for both hemochromatosis and PCT. The HLA heterozygosity for hemochromatosis in some patients with PCT may be a cause of hepatic siderosis.

Porphyrin metabolism in hepatitis C infection.

Hepatitis C virus has been implicated as a major precipitating factor in porphyria cutanea tarda (PCT). To determine whether hepatitis C infection alone is sufficient to induce PCT, we screened two groups of patients with hepatitis C infection. The first group comprised women who had become HCV positive secondary to immunization with anti-D immunoglobulin (group 1). Group 2 included males and females who were HCV positive but HIV negative secondary to intravenous drug abuse. Though both groups had very abnormal liver function tests, we found no significant abnormalities in porphyrin metabolism in these groups of patients. Therefore, in this study population, we conclude that HCV infection alone is insufficient to cause porphyrin metabolic derangement.