Retinoblastoma. Cell of origin.

OBJECTIVES: To apply modern techniques of molecular cell biology and to revisit the old question of the cell of origin for retinoblastoma in hopes of gaining a better understanding of the retinoblastoma gene's antioncogenic mechanisms. METHODS: Twenty-two consecutively accessed retinoblastomas were examined with immunocytochemical techniques for numerous retinal proteins. Both single and double labeling were used. Enzyme histochemistry for carbonic anhydrase was used as well. RESULTS: Differentiated areas of the tumors contained abundant Müllerlike cells. Fleurettes stained mostly for red and green cone-specific antibodies while features of blue cones and rods predominated in areas with high cytoplasmic-to-nuclear ratios but no fleurettes. All of the differentiated neoplastic cells were either photoreceptors or Müller's cells. No other retinal cell types were found. CONCLUSIONS: The cells of retinoblastoma are capable only of bipotential differentiation, ie, Müller's cells and photoreceptors. Given this and recent findings concerning retinal embryogenesis, we argue for the rod photoreceptor as the cell of origin. A possible role for the retinoblastoma gene product is discussed.

Relapsing polychondritis, another cause for a "salmon patch".

We present the case of a patient with long-standing relapsing polychondritis and, first, an orbital mass and, then, a "salmon patch" conjunctival mass. The histologic pathologic findings were similar on both occasions, showing an inflammatory process with reactive lymphoid hyperplasia. In both situations, the masses responded to a short course of systemic corticosteroids. Although ocular inflammatory changes from relapsing polychondritis have been well described, to our knowledge, there have been no previous reports of conjunctival changes in the form of a salmon patch lesion, as described here. Relapsing polychondritis may be added to the differential diagnosis of a conjunctival salmon patch lesion.

High-dose magnesium sulfate attenuates pulmonary oxygen toxicity.

BACKGROUND AND METHODS: Rats rapidly develop respiratory distress when exposed to 100% oxygen and die within a few days. Autopsy of the lung shows severe histologic damage characteristic of the adult respiratory distress syndrome. The purpose of this study was to evaluate the effects of magnesium sulfate loading in a rat model of acute oxygen toxicity. Thirty-four rats were divided into three groups. Group 1 (n = 18) served as a control (no magnesium therapy), while group 2 (n = 8) and group 3 (n = 8) received varying amounts of magnesium sulfate. All animals were exposed to 100% oxygen for 96 hrs or until death. Lung damage was quantitated by measuring the lung injury score on histologic examination. RESULTS: Administering magnesium sulfate in moderate doses at infrequent intervals to rats (group 2) resulted in less severe oxygen-induced lung damage than that which occurred in rats not receiving magnesium (control group). However, the difference was not statistically significant. Rats (group 3) given doses of magnesium sulfate in amount and frequency adequate to maintain a serum magnesium concentration recognized as therapeutic in eclampsia significantly reduced oxygen-induced lung damage. CONCLUSION: High-dose magnesium sulfate therapy can reduce lung injury caused by acute oxygen toxicity in rats.

Accumulation of p53 protein correlates with a poor prognosis in human lung cancer.

Mutations in the gene coding for the p53 tumor suppressor protein are common in a variety of human cancers. To assess the role of a putative mutated p53 protein in human lung cancer, a monoclonal antibody recognizing it was used in an immunoperoxidase detection system. A total of 114 cases of Stage I and II adenocarcinomas and squamous cell carcinomas were studied. The staining pattern was always intranuclear and heterogeneous. When the median or mean survival time was compared between cases, p53 accumulation had a statistically significant negative prognostic value. This was supported by a Kaplan-Meier survival plot of p53 producers and nonproducers. In 7 of 24 Stage II cases that were negative for p53 in the primary tumor, metastatic regional lymph nodes were p53-positive. These latter cases had greatly reduced survival times. Thus, p53 accumulation in primary tumors (and regional lymph nodes) may identify a subgroup of lung cancer patients with a prognosis of more aggressive disease.

Granulocytic sarcoma presenting as an epidural mass with acute paraparesis in an aleukemic patient.

Granulocytic sarcomas are rare tumors composed of granulocytic precursor cells. They are most commonly encountered in patients with acute myelogenous leukemias and myeloproliferative disorders in blast crisis. Rarely, patients presenting with granulocytic sarcoma show no evidence of acute leukemia. The authors report an aleukemic patient with acute paraparesis from an epidural granulocytic sarcoma. Only five such cases have been reported previously. Immunoperoxidase stain for lysozyme and chloroacetate esterase stain were used to prove the myeloid origin of the tumor cells.