24 September 2015 - Case of the Week #365

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Case of the Week #365

Clinical History:
A 59 year old man with hypothyroidism presented with headaches. Non-contrast magnetic resonance imaging (MRI) showed no CNS lesions, but a nodular mass in the right parotid gland.


Gross Description:
The lesion was completely excised, and was 3.7 x 2.3 x 2.0 cm, pink-tan, soft, fibroadipose tissue with a 1.7 x 1.1 x 1.0 cm well circumscribed glassy white tan nodule with yellow flecks abutting the inked surface. A preliminary diagnosis of myxoid neoplasm was made intraoperatively.


MRI images:
 

 

 

 



Micro images:
 

H&E images



What is your diagnosis?































Diagnosis:
Intraparotid neurofibroma

Discussion:

Special stains were obtained:
 

Alcian Blue

Ki-67

S100



Neurofibroma is a well-differentiated benign nerve sheath tumor composed of a variable mixture of Schwann, perineurial-like and fibroblastic cells. In the general population, neurofibromas are far more often sporadic than associated with neurofibromatosis.

Histolopathologic examination in this case showed the presence of a well-circumscribed, moderately cellular lesion composed of cells with wavy nuclei and eosinophilic cytoplasm interspersed with wisps of collagen and mucoid material. Mild nuclear atypia was noted. Mitotic figures were extremely rare (< 1/10 HPFs) and there was no evidence of necrosis. The tumor showed strong and diffuse reactivity with S100 and was negative for pankeratin and EMA. The proliferation index was less than 5%. Alcian blue highlighted the mucoid material within the tumor matrix. This constellation of features is classic for neurofibroma. In addition, mast cells are usually present in the microenvironment, although this feature is not specific.

Neurofibroma occurring in the parotid gland is extremely rare, constituting only 0.4% of all salivary neoplasms. When it does occur in this location, it is usually in patients with neurofibromatosis type 1 (NF-1). Solitary neurofibromas can occur in the absence of NF-1, and in this case, close monitoring is required to ensure that other stigmata of NF-1 do not develop in the future. Diagnostic confusion may arise when unaware of the possibility of a neurofibroma in this unsuspected site.

Morbidity is due primarily to facial nerve palsy and pain. Surgical removal is recommended for symptomatic patients and for those with NF-1 due to the risk of malignant transformation. Overall the prognosis is excellent, although potential complications of treatment may arise and vary depending on the location of the tumor. These include disease recurrence, facial nerve compromise and CSF leak.

References: Atlas of Tumor Pathology, Third Series, Fascicle 24: Tumors of the Peripheral Nervous System, Atlas of Tumor Pathology Tumors of the Central Nervous System (Atlas of Tumor Pathology 3rd Series), Indian J Surg 2011;73:224, Br J Plast Surg 2002;55:689, Laryngoscope 2003;113:82, AJNR Am J Neuroradiol 2006;27:126, Ear Nose Throat J 2012;91:236, Neurosurgery 1987;20:946, Neuroradiology 1993;35:614, J Otolaryngol Head Neck Surg 2011;40:104, Int J Morphol 2011;29:1054

Discussion by Dr. Jennifer R. Kaley, University of Arkansas for Medical Sciences (USA), Dr. Nicos Nicolaou, Lenox Hill Hospital (USA) and Dr. Oana Rafael, Lenox Hill Hospital (USA)