[MR Features of hepatic macronodular mycobacteriosis]

Hepatic macronodular mycobacteriosis is rare. Its diagnosis is challenging and is most often proposed on the basis of histological analysis. Final diagnosis, except for germ-proven cases, is made in conjunction with clinical, biological, and radiological arguments. We retrospectively report the MR features of ten hepatic lesions discovered on five patients. MRI is sensitive but has a low specificity in demonstrating pseudotumoral lesions most often exhibiting hypointensity on the T1-weighted sequence, hyperintensity on the T2-weighted sequence, and a slight rim enhancement after gadolinium-enhanced T1-weighted sequences.

MRI features of a pancreatic schwannoma

A case of a pancreatic schwannoma is presented. The patient, a previously healthy woman, is hospitalized with the diagnosis of purulent pleuritis. Ultrasonography (US) of the abdomen shows a 3-cm mass in the head of the pancreas. Magnetic resonance imaging (MRI) reveals, in T1-weighted sequences, the mass to be hypointense, and an early and persistent enhanced signal is noted following the administration of gadolinium. In T2-weighted fat saturation sequences, the lesion appears markedly hyperintense. A duodenopancreatotomy is performed, and the pathologic specimen demonstrates a schwannoma of the pancreas with Antoni A pattern.

Subcutaneous or intrahepatic injection of suicide gene modified tumour cells induces a systemic antitumour response in a metastatic model of colon carcinoma in rats

BACKGROUND

Suicide gene therapy consists of the transfer into tumour cells of a "suicide" gene that can convert a non-toxic compound into a lethal drug. Expression of the cytosine deaminase gene leads to the conversion of the non-toxic compound 5-fluorocytosine to 5-fluorouracil. We have recently shown that "suicide cell based vaccination" consisting of intrahepatic injection of cytosine deaminase expressing colon cancer cells followed by 5-fluorocytosine treatment induces regression of a distant wild-type liver tumour in rats.

AIMS

This study was conducted to test if (i) a distant bystander effect on a liver tumour can be induced after subcutaneous suicide cell based vaccination and (ii) suicide cell based vaccination is efficient in limiting tumour dissemination to extrahepatic compartments.

METHODS

An aggressive variant of rat colon carcinoma cells was selected after successive passages in vitro. Rats carrying an experimental liver "metastasis" generated by injection of these cells were vaccinated by subcapsular or subcutaneous injection of cytosine deaminase expressing cells followed by 5-fluorocytosine treatment.

RESULTS

Subcutaneous and subcapsular vaccination induced 70% regression in the median volume of the pre-established liver tumour (p=0.001) and abolished tumour dissemination compared with control animals.

CONCLUSIONS

This study has compared for the first time the efficiency of subcutaneous and intrahepatic suicide cell based vaccination in a metastatic colorectal carcinoma model in rats. The results indicate that both modes of vaccination are equally efficient in inducing a systemic antitumour response, suggesting that this strategy is a powerful approach against the development and dissemination of metastatic colon carcinoma.

Liver biopsy is not useful in the diagnosis of mycobacterial infections in patients who are infected with human immunodeficiency virus

Liver biopsy (LB) has been advocated for the detection of mycobacterial infections in patients infected with human immunodeficiency virus (HIV). To determine the effect of the use of this procedure on survival, we compared it terms of yield with histological findings and noninvasive microbiological procedures. We reviewed the cases of 98 patients who underwent 106 LBs as part of the diagnostic screening for fever of unknown origin. LB revealed 17 cases of mycobacterial infection. For all but one patient, the results of at least one noninvasive procedure were positive. In 85 cases where infections were not diagnosed by LB, 17 had infections documented by other procedures. When all culture results are considered, the mean (+/- SD) incubation time to the first positive culture was 15 +/- 5 days, whereas the mean (+/- SD) incubation time to the first positive culture of an LB specimen was 28 +/- 9 days. The survival time was not significantly increased for patients who underwent LB and had positive Ziehl-Neelsen-stained smears; these patients survived a mean (+/- SD) of 12 +/- 11 months, whereas patients with negative smears survived a mean (+/- SD) of 9 +/- 10 months. Noninvasive studies are preferable to LB for the diagnosis of mycobacterial infections in HIV-infected patients.

Hyperacute rejection of liver allografts in sensitized rats: role of nonparenchymal liver cells

Reasons why liver allografts are more resistant to antibody mediated rejection than other organ allografts are not fully understood. In order to define the role of nonparenchymal liver cells, we have compared the fate of liver allografts in two combinations of sensitized inbred rats. In the DA into LEW combination, hyperacute rejection of liver allografts was observed (mean survival time of liver grafted rats was 5.2 +/- 0.6 hr). A sharp decrease of the level of cytotoxic antibodies was observed after transplantation associated with deposits of IgG, IgM, C3, and fibrinogen on sinusoidal cells. Macroscopic and histological aspects of liver allografts were suggestive of an antibody-mediated rejection with congestion and portal hemorrhage. On the contrary, in the LEW into BN combination, survival time was significantly longer (259.2 +/- 25.2 hr), whereas histological studies demonstrated signs of cellular rejection. A decrease in the level of cytotoxic antibodies was present and deposits of IgG, IgM, C3, and fibrinogen were more significant. After blockade of the Kupffer cells of the LEW-transplanted liver, survival time of the BN rats was significantly reduced (38.8 +/- 8.0 hr). Macroscopic and histological aspects of the grafts were suggestive of antibody-mediated rejection and deposits of IgG, IgM, and C3 were reduced. The results suggest the hypothesis that resistance of liver allografts to antibody-mediated rejection is probably due to the ability of nonparenchymal liver cells to absorb preformed cytotoxic antibodies and complement.

Intestinal and extraintestinal Isospora belli infection in an AIDS patient. A second case report

A 30-year-old black female, from Burkina Faso, had AIDS in 1990. She died in March 1993 following a cachexia secondary to a chronic intestinal isosporiasis. The autopsy revealed a massive parasitic infection by I. belli of the small intestine mesenteric and mediastinal lymph nodes and liver and spleen. The parasite stage observed in extra intestinal sites corresponded to unizoite tissue cysts. This is the first report of I. belli infection in liver and spleen.

Pathological features of intestinal microsporidiosis in HIV positive patients. A report of 13 new cases

Enterocytozoon bieneusi is a microsporidian parasite found only in the enterocytes of the small bowel of HIV positive patients, producing chronic diarrhea and malabsorption. Since January 1990, we have seen the 13 first Mediterranean cases, diagnosed on duodenal pinch biopsy samples. Diarrhea was the major symptom in all instances, and E. bieneusi was the sole identified pathogen in 6 cases. The diagnosis was made on HES or Giemsa-stained paraffin sections and on Giemsa-stained smears (9 cases). In 3 cases, the parasite was also found on ileal biopsies, but was never encountered in the colonic mucosa. In all patients, transmission electron microscopy of the duodenal mucosa was used, and it confirmed the diagnosis of intestinal microsporidiosis. No instance with negative optic examination had evidence of an infection by E. bieneusi with electron microscopy. Due to the small size of the spores, routine fecal parasitological diagnosis is still a difficult procedure, but it is possible that greater experience may avoid many of today's invasive investigations. Cytologic and histologic routine examination of paraffin sections of the distal duodenal or ileal mucosae is a reliable method to diagnose intestinal microsporidiosis in HIV-positive patients with diarrhea.