A pulmonary blastoma is reported in a 19-year-old black female. The light and electron microscopic characterics are described; they are found to be similar to those of the fetal lung prior to the fourth gestational month. Although the ultrastructural features do not favor any particular theory of histogenesis of this unique tumor, evidence for the commonly held theory that the tumor arises from pluipotential pulmonary blastema seems tenuous. A brief review of the literature disclosed 38 other similar cases. There was a male predominance with an average age of detection at 39 years. Sputum cytology was rarely positive. Among tumors larger than 5 cm in diameter, survival was usually less than 2 years. Metastases were present in approximately half of the cases.

Postoperative spindle-cell nodule of the urinary bladder (or in the absence of previous surgical procedure, inflammatory pseudotumor) is a reactive process of unknown etiology mimicking a sarcoma. Intracytoplasmic inclusion bodies were noted inside the atypical spindle cells on Diff-Quik stained smears in a recent case of this entity. Although fluorescence was noted in the inclusion bodies with monoclonal antibodies against the major outer membrane protein of the Chlamydia species, the exact nature of these inclusion bodies remains unknown.

A case of cystadenoma of the pancreas was studied at the light (LM) and the ultrastructural (EM) levels. The observation made under LM that the flattened epithelial cells lining the cystic spaces were similar to the centroacinar cells of a normal pancreas was supported by EM findings. Numerous glycogen granules were demonstrated in the cells, a feature characteristic of fetal but not adult centroacinar cells. A few epithelial cells contained occasional membrane bound dense granules of unknown nature. This observation and the finding of normally appearing islets of Langerhans raise the possibility that this may be an example of a mixed insular-duct cystadenoma. However, if the islets of Langerhans were considered entrapped structures, this tumor should be labelled as a simple serous cystadenoma.

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