Lipochoristomas (lipomatous tumors) of the acoustic nerve.
BACKGROUND
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.


METHODS
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.
Department of Pathology, St Vincent Medical Center, Los Angeles, Calif, USA.
Sandy S
SS
Wu
William W M
WW
Lo
Donald L
DL
Tschirhart
William H
WH
Slattery
Joseph N
JN
Carberry
Derald E
DE
Brackmann
D000328:Adult; D002528:Cerebellar Neoplasms / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology*; D002530:Cerebellopontine Angle / Q000000981:diagnostic imaging / Q000473:pathology; D003056:Cochlear Nerve / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D003390:Cranial Nerve Neoplasms / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D005500:Follow-Up Studies; D005557:Formaldehyde / Q000378:metabolism; D034381:Hearing Loss / Q000209:etiology; D006801:Humans; D007150:Immunohistochemistry; D008067:Lipoma / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D016612:Paraffin Embedding; D016707:Tissue Fixation; D014057:Tomography, X-Ray Computed / Q000379:methods; D000159:Vestibulocochlear Nerve / Q000000981:diagnostic imaging / Q000473:pathology
D005557:Formaldehyde