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ULTRASOUND N May 2007 N Volume 15 N Number 2
Multifocal Nodular Oncocytic
Hyperplasia (MNOH) of the Parotid
Gland: A report of two cases
Peter Thurley, Ivan Robinson & Neil Cozens
Department of Radiology, Derbyshire Royal Infirmary, London Road, Derby, UK, DE1 2QY
A neck ultrasound examination demonstrated two hypo-echoic
Introduction lesions within the parotid (Fig. 3), both of which measured
15 mm in short axis diameter. The more posterior lesion
Multifocal nodular oncocytic hyperplasia (MNOH) is a benign showed minimal flow on power Doppler examination, but the
condition that occurs predominantly in the parotid gland. It inferior and anterior lesion appeared hypervascular (Fig. 4).
consists of two or more distinct oncocytic foci that are FNA was performed separately on both of the lesions.
interspaced with normal tissue.1 We describe two cases of Microscopy of the FNA of the less vascular lesion was
MNOH, review the imaging features, and discuss the consistent with a benign cyst, such as a lympho-epithelial
differential diagnosis and possible diagnostic pitfalls. cyst or Warthin’s tumour. Microscopy of the FNA of the second
parotid lesion revealed appearances of an oncocytic acinic
salivary neoplasm. In view of these findings, this patient
underwent superficial parotidectomy and selective neck
Case 1 dissection.
Histology of the parotid specimen showed MNOH. One
A 53-year-old man was referred to the ENT department with a nodule had an area of cystic degeneration that had mimicked
left parotid mass, detected as an incidental finding whilst an acquired salivary cyst. Post-operatively the patient
consulting his GP for epistaxis. Following review by the ENT remained well.
team he underwent ultrasound examination (Fig. 1). This
demonstrated multiple hypo-echoic nodules measuring up to
10 mm in short axis diameter. The nodules appeared
hypervascular on power Doppler examination. Much less Discussion
extensive involvement of the right parotid was noted. The
submandibular salivary glands were normal and there was no Oncocytic tumours of the salivary glands are rare,2 occurring
evidence of locally enlarged lymph nodes. In view of these most commonly in the parotid3 and less frequently within the
findings, fine needle aspiration (FNA) was performed.
submandibular gland. MNOH can be distinguished from other
Microscopy was consistent with a salivary neoplasm of acinic
oncocytic lesions (such as oncocytoma or diffuse oncocytosis)
or ductal type, and excision to allow further assessment was
by histological criteria. MNOH tends to be uncapsulated and
advised.
show oncocytic sheets. This condition has been reported to
Prior to surgery, an MRI scan of the face and neck was occur in a slightly younger age group to oncocytoma (a mean
performed to characterise the lesions further. This demon- of 47 versus 77 years in a recent series4). MNOH tends to
strated multiple solid nodules within the parotid glands present as a parotid mass that is usually non-tender, as in
bilaterally, more numerous on the left, which were low signal these two cases, but may be painful if there has been
on T1 weighted images and intermediate signal on STIR haemorrhage into the lesion.4 In our cases, the imaging
images (Fig. 2). Radiologically, this appearance was indeter- findings were of multiple discrete lesions measuring up to
minate, but suspicious, with the combination of multiple solid
vascular lesions in the absence of pathological cervical
lymphadenopathy and the FNA result above warranting
surgical excision.
The patient underwent a left total parotidectomy. Histology
of the resected specimen showed MNOH, clear cell variant.
Unfortunately, during the procedure, he sustained an injury to
his left facial nerve and was left with a post-operative lower
motor neurone palsy. The patient has not yet had surgery for
his right parotid lesions.
Case 2
A 79-year-old man presented with a 6-week history of a
painless right infra-auricular mass with no systemic symptoms.
Correspondence: Dr P. Thurley, Department of Radiology, Derbyshire
Royal Infirmary, London Road, Derby, UK, DE1 2QY. peter.thurley@ Figure 1. Ultrasound of the left parotid showing multiple hypo-echoic
ntlworld.com lesions.
Ultrasound 2007;15(2):68–70 DOI: 10.1179/174313407X181064
ß British Medical Ultrasound Society 2007
68
Thurley Multifocal Nodular Oncocytic Hyperplasia (MNOH) of the Parotid Gland: A report of two cases
(a) (b)
Figure 2. (a) T1-weighted and (b) STIR sequences showing multiple nodules within the parotid glands (arrows).
15 mm in maximum short axis diameter within the parotid, on ultrasound and appeared solid on MRI. This contrasts with
without any associated enlarged lymph nodes. In one of the a previous case report,5 which described their lesions as
cases the process was bilateral. The lesions were hypo-echoic appearing cystic with both sonography and MRI.
Figure 3. Hypo-echoic areas within the right parotid.
69
ULTRASOUND N May 2007 N Volume 15 N Number 2
Figure 4. Hypervascularity demonstrated on power Doppler.
On histological examination MNOH are mostly composed of prior to surgical removal of the lesion. Head and neck
unencapsulated nodules of oncocytic cells; clear cell change radiologists, sonographers and cytopathologists therefore
is usually seen and can predominate.6 Clear cells can be seen need to be aware of this rare lesion.
as a component of any benign or malignant salivary gland
tumour,7 as well as in metastases from renal cell carcinoma,
thyroid carcinoma and malignant melanoma.8 As the parotid
gland is not encapsulated, MNOH can give the false References
impression of invasion, which can make it difficult to
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Clear cell change does not distinguish benign from malignant oncocytosis: case report. J Oral Maxillofac Surg 2005;63:560–
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bland.9 2. Alberty J, August C, Stoll W. Oncocytic neoplasms of the parotid
Because of this it has been suggested that FNA may be less gland. Differential diagnosis, clinical course and review of the
accurate for the diagnosis of oncocytic tumours than other literature. HNO 2001;49:109–117.
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for FNA for salivary oncocytic tumours (n 5 21), compared O. Multifocal nodular oncocytic hyperplasia of the parotid: case
with .90%, which has been reported for other salivary report. Ann Pathol 2002;22:215–218.
tumours.10 In both of our cases the FNA was unhelpful in 4. Palmer TJ, Gleeson MJ, Eveson JW, Cawson RA. Oncocytic
making the diagnosis. adenomas and oncocytic hyperplasia of salivary glands: a
clinicopathological study of 26 cases. Histopathology
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5. Strassburger S, Hyckel P, Kosmehl H. Multifocal oncocytic
the parotid gland when considering the possibility of MNOH. adenomatous hyperplasia of the parotid gland. A case report. Int
Multiple parotid cysts in Sjogrens’ are associated with J Oral Maxillofac Surg 1999;28:457–458.
xerostomia. Lymphoma is often associated with local cervical
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lymphadenopathy and can usually be confirmed on FNA salivary glands. J Clin Pathol 1992;45:369–377.
cytology, even if isolated within the parotid. Warthin’s or
7. Triantafillidou E, Dimitrakopoulos I, Skordalaki A. Clear cell
intraparotid metastases are also readily diagnosed on FNA
carcinoma of the minor salivary glands. Report of a case. Aust
cytology. Multifocal pleomorphic adenomas are very rare in Dent J 1997;42:8–10.
the absence of previous surgical intervention. Multiple
8. Seifert G. Classification and differential diagnosis of clear and
lymphoepithelial cysts are most commonly found in HIV
basal cell tumours of the salivary glands. Sem Diagnost Pathol
positive patients.11 1996;13(2):95–103.
Whilst the biological behaviour of MNOH is incompletely 9. Eversole LR. On the differential diagnosis of clear cell tumours of
understood, the treatment of choice for MNOH is surgical the head and neck. Oral Oncol Eur J Cancer 1993;29B:173–179.
resection and recurrence may occur if the lesion is not 10. Capone RB, Ha PK, Westra WH, Pilkington TM, Sciubba JJ, Koch
completely removed.5 However, it is still useful to be able to WM, Cummings CW. Oncocytic neoplasms of the parotid gland:
distinguish MNOH from a malignant lesion prior to surgery as a 16-year institutional review. Otolaryngol Head Neck Surg
this may allow less extensive resections to be attempted. This 2002;126:657–662.
may have benefited the two patients described here. By 11. Favia G, Capodiferro S, Scivetti M, Lacaita MG, Filosa A, Muzio
combining the cytological findings with the radiological and LLO. Multiple parotid lymphoepithelial cysts in patients with HIV-
clinical findings, a more accurate diagnosis may be made infection: report of two cases. Oral Dis 2004;10(3):151.
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