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Lipochoristomas (lipomatous
tumors) of the acoustic nerve. Arch Pathol Lab Med.2003
Nov;127(11):1475-9.
CONTEXT:
Lipochoristomas (lipomatous choristomas) are rare tumors of the
acoustic nerve (cranial nerve VIII/vestibulocochlear nerve) within
the internal acoustic canal and sometimes the cerebellopontine
angle, and are histogenetically believed to be congenital
malformations. Their clinically indolent behavior has recently
prompted a more conservative management protocol in a quest for
maximal nerve/hearing preservation. This approach contrasts sharply
with that for the common internal acoustic canal/cerebellopontine
angle tumors, the neuroepithelial neoplasms (acoustic schwannomas
and meningiomas), which behave more aggressively and have more
prominent clinical manifestations. Owing to their rarity, the
clinicopathologic features of cranial nerve VIII lipochoristomas
have been obtained mainly through case reports. OBJECTIVE: We
present the clinicopathologic features of 11 cases of
lipochoristomas of cranial nerve VIII. DESIGN: The 11 cases were
documented between 1992 and 2003. We performed complete clinical
reviews with histologic, histochemical, and immunohistochemical
analyses of formalin-fixed, paraffin-embedded tumor samples.
RESULTS: The patients were 8 men and 3 women with hearing loss of
the right ear (5 patients) or the left ear (6 patients). No patient
had bilateral tumors. All lipochoristomas histologically possessed
mature adipose tissue admixed with varied amounts of mature fibrous
tissue, tortuous thick-walled vessels, smooth muscle bundles, and
skeletal muscle fibers, the latter verified with
immunohistochemistry. CONCLUSIONS: The histomorphologic and
immunophenotypic evidence showed that these tumors are better
characterized as choristomas than as simple "lipomas," as
they have been labeled in the past. Their overall nonaggressive
clinical nature in addition to the characteristic radiologic and
histomorphologic findings are important clinicopathologic features
for the pathologist to recognize and differentiate, especially
during frozen section evaluations, in order to direct the
neurosurgeon to a more appropriate conservative therapeutic
intervention.
Acoustic Nerve
Tumors: Early Diagnosis and Treatment. 2nd ed. Springfield, Mass:
Charles C Thomas; 1970.
Pathology of the
Ear. Cambridge, Mass: Harvard University Press; 1974.
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