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PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
1991-9-11
pubmed:abstractText
Spontaneous amelanotic melanocytic tumors of the pinna were found in six females of 960 male and 960 female albino (F344/DuCrj) rats which had been used in three different 24-month chronic toxicity studies. The age when the pinnal tumors were detected ranged from 37 to 59 weeks. The tumors were located unilaterally in the pinna and observed as subcutaneous spherical to irregular, solid white masses measuring 7 to 25 mm in diameter. The pinnal tumors were histologically classified into spindle cell and pleomorphic cell types. The spindle cell type was observed in four rats and composed of fusiform cells arranged in interlacing bundles. The pleomorphic cell type was observed in the remaining two rats and composed of pleomorphic large cells arranged in sheets. One tumor of the latter type metastasized to the submaxillary lymph node and lung. Melanin pigments were not demonstrated in any of the tumors. In immunohistochemistry, nuclei and cytoplasm of tumor cells in all the tumors were slightly positive for S-100 protein. Ultrastructurally, tumor cells contained a considerable number of premelanosomes in the cytoplasm. Desmosomes were occasionally observed between the cell membranes of the adjacent tumor cells. No distinct basal lamina was seen around tumor cells.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0916-7250
pubmed:author
pubmed:issnType
Print
pubmed:volume
53
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
291-6
pubmed:dateRevised
2003-11-14
pubmed:meshHeading
pubmed:year
1991
pubmed:articleTitle
Amelanotic melanocytic tumors of the pinna in six F344 rats.
pubmed:affiliation
Toxicology Division, Institute of Environmental Toxicology, Tokyo, Japan.
pubmed:publicationType
Journal Article