Spontaneous melanocytosis in transgenic mice.

Clone B is a 2-kb fragment of cloned genomic DNA involved in adipocyte differentiation in vitro. Insertion of this DNA fragment into the genome of a variety of cell lines results in committing the recipient cells to undergo adipocyte differentiation. Construction of transgenic mice with Clone B DNA resulted in an unexpected phenotype--spontaneous melanocytosis. The present study describes the distribution and morphology of melanin-containing lesions in these transgenic mice. Spontaneous melanin-containing dermal lesions appeared on the ears, snout, and perianal regions of transgenic mice by the age of 3-4 months. Multifocal dermal masses rapidly developed into raised lesions, which appeared to spread to adjacent skin. Ultrastructural examination of lymph nodes, spleen, and dermal lesions of these mice revealed membrane-bound melanin with effacement f the organelle structure of severely affected cells. Protein gel electrophoresis revealed elevated activity of tyrosinase in the pinnae, skin, perianal mass, and lymph nodes. This line of transgenic mice may provide a useful model for investigation of the etiology and progression of benign and malignant melanin-containing tumors.

Human disease caused by dog heartworm.

Pulmonary infection with D. immitis is an infrequently reported cause of lung disease in humans. Approximately 80 cases have been reported in the United States, with increasing numbers reported in recent years. The largest single series from one institution is a series of 6 patients from Ochsner Clinic in New Orleans, Louisiana. Although our series consisted of 3 females and no males, the disease is detected and diagnosed in males twice as often. The usual age range is 40 to 60 years. No case has yet been seen in children. Unfortunately, it is essentially impossible to diagnose by clinical means. The definitive diagnosis can be made quite easily, however, by histologic examination which reveals the worm within the lesion. It should be noted that the parasites are seen in a minority of sections; therefore, diagnosis may be missed. As a result, given the setting of pulmonary infarction with granulomatous response, multiple sections of the lesion should be examined. Other larval worms also occurring in the lung which might be confused with D. immitis include Enterobius vermicularis, Wuchereria bancrofti, Brugia malayi, and Onchocerca volvulus. These, however, are much less common and are morphologically distinct from D. immitis. Also, it is easily distinguished from ascarids, strongyloids, and hookworm larvae which are much smaller than the dirofilarial worms and do not contain reproductive organs. In North American, the occurrence of fragments of nematode within a pulmonary infarct is essentially pathognomonic for PD.

Fibrolamellar carcinoma: distinctive clinical and morphologic variant of hepatoma.

We present two cases of fibrolamellar carcinoma. Because of its usual presentation as a solitary mass in the noncirrhotic liver of a young girl, this tumor is likely to be mistaken clinically for a benign lesion. Its microscopic appearance is unique and easily separated from other types of hepatocellular carcinoma, an important distinction because of the better prognosis of fibrolamellar carcinoma.

Thyroid lymphoma with adjacent nerve paralysis.

Although local nerve invasion in thyroid lesions is most commonly found with anaplastic carcinoma, it does not rule out lymphoma. Open biopsy is most helpful in the diagnosis of lymphomas. Ultrastructural studies are often necessary for confirmation of the diagnosis. Differentiation between lymphoma and anaplastic carcinoma of the thyroid is very important since the treatment is substantially different and the prognosis is much better with lymphoma. To our knowledge, the case presented represents the first case of Horner's syndrome secondary to lymphoma that has been documented in the literature.

Blastomycosis of the larynx.

Blastomycosis is an uncommon fungal disease which may mimic carcinoma of the larynx. Physical examination may show a granular appearance early in the disease with progression to laryngeal fibrosis. Histologic examination usually shows pseudoepitheliomatous hyperplasia, microabscesses, and giant cells. The broad-based budding yeast organisms may be easily overlooked unless special stains are used. Two cases of laryngeal blastomycosis which were originally treated as carcinoma are reported.

Microtubular aggregates in the rough endoplasmic reticulum of a myxoid chondrosarcoma.

A tumor with the light microscopic and histochemical characteristics of myxoid chondrosarcoma is examined ultrastructurally. Instead of the usual features of chondroblasts, the tumor cells exhibited prominent collections of long straight microtubules within the endoplasmic reticulum. This finding is compared with other previously reported tubular aggregates. The differential diagnosis and ultrastructure of myxoid chondrosarcoma are also discussed.

Trophoblastic pseudotumor: An illustrative case.

A case of trophoblastic pseudotumor of the uterus is presented. Erroneous interpretations of the specimens derived from curettage and hysterectomy resulted in surgery and chemotherapy. Emphasis in this report is on histologic criteria which aid in distinguishing this lesion from choriocarcinoma. Hormone production and persistence of the tumor for several months after curettage are also documented.

Focal nodular hyperplasia of the liver with alcoholic hyalin bodies and cytologic atypia.

Focal nodular hyperplasia is an uncommon hepatic lesion in which the component hepatocytes are usually histologically normal. A case of focal nodular hyperplasia with cytologically atypical hepatocytes is presented. Light and electron microscopic evidence is given for the presence of alcoholic hyalin in these cells. A review of cytologic changes reported in focal nodular hyperplasia by others is included. To our knowledge, the presence of alcoholic hyalin in focal nodular hyperplasia has not previously been reported.