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A Rare Case of Non-Hodgkin Lymphoma of the Parotid Gland: A Cytological Diagnosis

 

 

Article By:

A. Fernandes

D. Prabhugaonkar

R.G.W. Pinto

 

Abstract

A primary malignant lymphoma of the salivary gland is very rare, with most cases arising in the parotid gland. Clinical presentation is not usually characteristic, and the disease is often overlooked with a delay in the diagnosis and treatment. Here, we present a rare case of non-Hodgkin lymphoma arising in the parotid gland.

 

Introduction:

Although the head and neck region are the most common site where malignant lymphomas can occur; a lymphoma of the salivary gland is relatively uncommon. Primary non-Hodgkin lymphoma (NHL) of the salivary glands comprises of 5% of all primary extranodal NHL and 2% of all salivary gland neoplasms.[1,2] Among these, 75% arise within the parotid gland.[2,3] It can either arise from an intra-parotid lymph node, or within the gland itself. Clinically most cases present as unilateral masses. The large majority of salivary gland lymphomas are of B-cell origin, most commonly extranodal marginal zone B-cell lymphoma of the mucosa-associated lymphoid tissue (MALT) type, follicular B cell lymphoma and diffuse large B-cell lymphoma.[4,5]

 

Case Report:

A 33-year-old female presented to the neurology department with complaints of loss of smell (anosmia) and decreased hearing in the left ear. Patient was a known case of multiple cranial neuropathies, that was diagnosed one year ago.  On examination, there was a swelling in the right preauricular region measuring 3 x 2 centimetres. The swelling was a firm, nodular swelling.

An ultrasound was done of the swelling which suggested a nodal mass in the right parotid region with a provisional diagnosis of sarcoidosis or lymphoma.

A fine needle aspiration cytology (FNAC) done of the swelling revealed a cellular smear with heterogenous population of large atypical lymphoid cells with round to irregular nuclear borders, prominent nucleoli with finely granular chromatin and abundant cytoplasm (Figures 1 and 2).

TC-July2018-003 - Hypercellular smear with a cluster of lymphocytes

 

Based on these findings, a diagnosis of non-Hodgkin lymphoma was made.

 

Discussion

Primary lymphomas of the salivary glands are very uncommon, only a small number of cases have been described in the literature. Most of the NHLs arise primarily in the lymph nodes (71.9%) while only 28.1% are primarily extranodal. The major salivary glands are affected in only 5% of all primary extranodal malignant lymphomas. The parotid is the most common salivary gland involved although primary parotid lymphomas account for only 0.87% of all NHL cases. This is the reason it is rarely suspected before biopsy or surgical removal.[6]

Parotid gland NHL generally presents as painless, slow growing mass on the parotid region clinically. Primary salivary gland lymphomas show parenchymal involvement of the parotid gland without lymph node differentiation.[7]

Most of  the  lymphomas  on  the  parotid  region are mucosa-associated  lymphoid tissue (MALT) lymphomas of the NHL. According to  medicalhistory, MALToma or MALT lymphomas are mostly related to chronic inflammatory processes such as Sjogren’s Syndrome or any chronic inflammation.

TC-July2018-004 - Atypical lymphocytes with heterogenous population of large atypical lymphoid cells

Rosenstiel et al. emphasized that Sjogren’s syndrome provoked a 44 times increased risk of lymphoma and 80% of these lymphomas are MALTomas.[8]  Klussmann  et  al.  suggested  that  MALToma was associated with the Ebstein-Barr virus (EBV), Human herpesvirus (HHV) subtypes 6 and 8, Hepatitis C virus (HCV), and human immunodeficiency virus (HIV) infections.[9] Additionally, malignant salivary gland lymphomas are mostly seen in patients over 50 years and are twice as much more common in females.[7]

Differential diagnosis of NHL includes many other types of the parotid gland tumors. Warthin’s tumor, pleomorphic adenoma, adenoid cystic carcinoma, mucoepidermoid carcinoma and adenocarcinoma may all contain cystic parts. Also, benign form of parotid gland tumors such as basal cell adenomas can lead to a misdiagnosis.[7]

Diagnostical radiological investigation can be done for parotid NHL but most of them reveal nondiagnostic findings. Pathologic investigation is the gold standard method for parotid gland NHL. This investigation needs pathological sampling such as fine needle aspiration biopsy (FNAB), excisional or incisional biopsy. FNAB is a reliable method for diagnoses of the salivary gland masses. But this method, like other lymphomas, is sometimes not sufficient for the diagnosis. Aydin et al. reported that FNAB is not completely sufficient for NHL.[7]

The differential diagnosis of discrete immature round cells with scanty deep blue cytoplasm at this site are alveolar rhabdomyosarcoma, acute monocyticleukemic deposits, peripheral neuroectodermal tumors (PNET), small cell carcinoma of the tongue, lymphoepithelial sialadenitis (LESA) and Warthin’s tumor.[10,11] However, discrete cells with scanty cytoplasm and lymphoglandular bodies in the background indicated a possibility of lymphoid origin of these cells.

Alveolar rhabdomyosarcoma was excluded by absence of large pleomorphic tadpole shaped tumor cells with eosinophilic cytoplasm and these cells are positive for the vimentin and desmin. Absence of nuclear molding, prominent nucleoli and pseudo rosette excludes PNET, which is positive for neuron-specific enolase. An acute leukemic deposit in the tongue is difficult to diagnose by morphology alone, but peripheral blood and bone marrow along with the cytochemistry may be helpful in the diagnosis. Small cell carcinoma shows dispersed cells with bare nuclei, teardrop and smeared cells in the background. The cells show nuclear molding, coarse nuclear chromatin and nucleoli.[11] The cytology of LESA reveals a mixture of acinar cells, epithelial, and myoepithelial cells admixed with polymorphous lymphoid cell population. Oncocytes can be encountered. Demonstration of clonal lymphoid population by IHC or flowcytometry differentiates it from MALT lymphoma. Warthin’s tumor is considered a benign primary parotid gland neoplasm that is composed of a mixture of oncocytic cells, basal cells, and stroma that contains numerous lymphocytes usually arranged in papillary and cystic structures. Lymphomas lack the oncocytic cells. By contrast, the diagnosis of non-MALT high grade lymphomas is usually straightforward, as they have overt cytological atypia.[10]

 

TC-July2018-005 - Authors Pg09

 

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