Teiko Sato

Myoid Cells in the Human Thymus and Thymoma Revealed by Three Different mmunohistochemica Markers for Striated Muscle

Specimens of human thymus and thymoma obtained from 81 patients including 22 with myasthenia gravis (MG), ranging in age from 10 weeks of gestation to 75 years were examine by the indirect immunoperoxidase technique using three different striated muscle markers: myoglobin, CPK‐mm and β‐enolase. Myoid cells ovoid or elongated in shape were distributed in the medulla and showed positive immunoreactions for myoglobin, CPK‐mm and β‐enolase by light and electron microscopy. The antigens were first detectable immunohistochemically in the fetus at the 10th week of gestation and showed a relative increase in number and varying distribution patterns with age involution in non myasthenic thy muses. In MG cases, the number of myoid cells was smaller than in non‐myasthenic cases, especially in markedly involuted thymuses. Myoid cells were occasionally observed within thymomas in areas showing medullary differentiation. Small numbers of cells showing a positive immunoreaction for β‐enolase but not for myoglobin and CPK‐mm were scattered in the area predominantly composed of epithelial cells. These cells were occasionally positive for keratin and showed desmosome‐like structures but no apparent myofilaments, suggesting that muscle‐like differentiation of epithelial cells might occur in the neoplastic process of thymoma. Acta Pathol. Jpn. 39: 509∼519, 1989.

Pulmonary inflammatory pseudotumor observed by bronchoscopy and resected using video-assisted thoracic surgery

Pulmonary inflammatory pseudotumor is rare. A 34-year-old woman visited our hospital due to an abnormal chest shadow. Computed tomograhy showed a nodule in the right upper lobe. Bronchoscopy showed a polypoid endobronchial nodule obstructing most of the orifice of B2a. The nodule was white, glossy, and smooth, and it seemed to be covered with bronchial mucosa. However, transbronchial biopsy could not facilitate a diagnosis. To obtain a definitive diagnosis, we performed lobectomy of the right upper lobe using video-assisted thoracic surgery and removed the nodule completely. The pathologic diagnosis made during surgery was inflammatory pseudotumor. Immunohistochemical examination showed proliferating spindle cells were positive for vimentin and smooth muscle actin, but negative for epithelial markers. These findings were consistent with the staining pattern of inflammatory pseudotumor previously reported. Careful follow-up is necessary to detect any sign of local recurrence and distant metastases.

Granular-cell tumorlike Schwann cell degeneration in the anal sphincter of an infant suspected of having ultrashort Hirschsprung's disease

A 19-month-old girl who had a history of constipation since birth and suspected cytomegalovirus (CMV) infection was admitted. Barium enema revealed no caliber change in the colon, anorectal manometry failed to show sphincter relaxation on rectal distension, and biopsied rectal specimens contained ganglion cells. She underwent rectal myectomy, after which her symptoms improved significantly. Morphologic studies, including electron micrographs of the muscle, demonstrated nerve plexuses with degenerative Schwann cells containing abundant eosinphilic cytoplasmic granules that resembled those of a granular-cell tumor. Granular-cell tumorlike change of the plexus is an unprecedented finding in any form of Hirschsprungs disease or its allied disorders, but appears to have been responsible for her symptoms. CMV as a causative agent is also discussed with a review of the literature.