lymphoma is a heterogeneous malignancy of the lymphatic system characterized by proliferation of lymphoid cells or their precursors .
they are generally categorized as hodgkin 's and non - hodgkin 's lymphomas ( nhls ) based on the presence and absence of typical hodgkin 's cells .
hodgkin 's lymphoma rarely presents as extranodal disease , whereas nhl commonly presents at extranodal sites ( 2545% ) such as gastrointestinal tract , skin and bone . in the head and neck , primary
nhl occurs in waldeyer 's ring , oral mucosa , salivary glands , paranasal sinuses , laryngeal tissue and bone .
when it does occur , mandibular nhl closely mimics an ameloblastoma , a tumor of odontogenic epithelial origin , both clinically and radiographically .
genetic diseases , environmental agents and infectious agents have been attributed to the development of nhl .
barr virus , human t - cell lymphotropic virus 1 , human immunodeficiency virus , helicobacter pylori , chlamydia and human herpesvirus-8 are known to be associated with an increased risk of nhl . while the actual role of viruses in lymphomagenesis remains to be understood , some types of nhl have shown insertion of exogenous genes by oncogenic viruses .
we present a rare case of rapidly progressing swelling of the left mandible which on routine histopathological examination appeared to be a spindle - cell sarcoma .
immunohistochemical analysis enabled a final diagnosis of spindle - cell variant of lymphoma , an occurrence previously reported only once in english literature .
a 64-year - old male presented with a rapidly progressive swelling of the left mandible since 6 months for which he had undergone fine needle aspiration cytology and an incisional biopsy elsewhere with a diagnosis of benign mesenchymal neoplasm and chronic inflammatory granulation tissue , respectively .
extraoral clinical examination revealed a firm to hard diffuse soft tissue swelling measuring 4 cm  5 cm that extended anteroposteriorly from midline to the left angle of the mandible and inferiorly extended 2 cm below the inferior border of the mandible [ figure 1a and b ] .
intraorally , buccal cortical expansion was noted from midline to second molar region obliterating the vestibule with paresthesia of lower lip [ figure 1c ] . overlying skin and mucosa
( a and b ) extraoral examination of left mandibular swelling that was firm to hard diffuse soft tissue swelling extending anteroposteriorly from midline to the left angle of the mandible and inferiorly extended 2 cm below the inferior border of the mandible .
( c ) intraoral view showing the unilateral ( left ) involvement of the lesion cone beam computed tomography ( planmeca promax 3d ; large fov [ 200 mm  100 mm ] ) imaging revealed an ill - defined , moth - eaten radiolucency in the left mandibular premolar / canine region with destruction of buccal and lingual cortical plates [ figure 2a  d ] .
serum calcium , phosphorous , alkaline phosphatase and parathyroid hormone levels were within normal limits .
( a ) cone beam computed tomography reconstructed panoramic image showing diffuse radiolucency in the left body of mandible extending superiorly to the alveolar crest and inferiorly to lower border ; anteriorly to apex of 33 and posteriorly till the region of 36 . ( b )
cone beam computed tomography coronal section showing radiolucent lesion in the left body of mandible extending through buccal and lingual cortex , minimal mucosal thickening of the right and left maxillary sinus floor is seen .
( c ) cone beam computed tomography sagittal section revealed radiolucency extending from 33 to 38 with erosion of the mandibular nerve canal .
( d ) cone beam computed tomography axial section showing asymmetry on left side with loss of buccal and lingual cortical plates and no evidence of expansion of the cortical plates a clinically aggressive growth in the mandible with radiographic evidence of bone destruction entailed a differential diagnosis of ameloblastoma , malignant salivary gland tumor , aggressive osteomyelitis , malignant connective tissue neoplasm and metastasis from unknown primary , thereby warranting a mandibular resection .
gross examination of the resected hemimandible showed attached lesional soft tissue measuring approximately  10.5 cm  8.0 cm  5.0 cm ,  white to brown in color , with multiple cystic spaces and no  crackling  upon palpation [ figure 3a ] .
microscopic examination showed an encapsulated lesion situated in the connective tissue and separated from the overlying normal epithelium by a grenz zone [ figure 3b ] .
morphologically , the neoplastic tissue showed a mixture of proliferating spindle - shaped cells arranged in fascicles and round cells infiltrating into the connective tissue stroma and bone [ figure 3c ] .
the neoplastic cells exhibited atypical features such as pleomorphism , hyperchromatism and increased mitotic figures with noncleaved nuclei [ figure 3d ] .
( a ) gross surgical specimen showing the erosion and perforation of the buccal and lingual cortical plates . cut surface of the tumor showing lingual invasion below the inferior border of mandible .
( b ) : photomicrograph showing presence of mixture of spindle- and round - shaped cells arranged in fascicles separated from normal epithelium by grenz zone ( h&e stain , 40 ) .
( c ) photomicrograph showing tumor cells infiltrating the bone ( h&e stain 40 ) .
( d ) : photomicrograph showing round to spindle shaped tumor cells with hyperchromatic nuclei ( h&e stain , 400 ) immunohistochemical staining with desmin [ figure 4a ] , smooth muscle actin ( sma ) [ figure 4b ] , s-100 [ figure 4c ] and cd1a [ figure 4d ] were negative and lymphoid markers leukocyte common antigen ( lca ) and cd20 ( cluster differentiation marker for b - cells ) showed positivity in spindle - shaped cells as well as round cells indicating the tumor to be a lymphoproliferative lesion of b - cell type [ figure 4e and f ] .
a final diagnosis of  spindle - cell variant of nhl  was rendered based on the immunohistochemical profile .
round- and spindle - shaped tumor cells showing negativity for ( a ) desmin ( ihc stain , 400 ) ; ( b ) smooth muscle actin ( internal positive control ; vessel wall ) ( ihc stain , 400 ) ; ( c ) s-100 ( internal positive control ; nerve ) ( ihc stain , 400 ) , ( d ) cd1a ( ihc stain , 400 ) . the cells were positive for ( e ) ; leukocyte common antigen ( lymphoid lineage marker ) ( ihc stain , 200 ) ; and ( f ) cd20 ( b - cell marker ) ( ihc stain , 200 ) postsurgical management of the patient was uneventful , and the disease was classified as ann arbor stage iie based on the involvement of the mandible and submandibular lymph nodes .
the patient underwent chemotherapy vide the cyclophosphamide , adriamycin , vincristine and prednisolone regimen and has remained disease free for 12 months of follow - up .
lymphoma is a malignancy of the lymphatic system characterized by proliferation of lymphoid cells or their precursors with purely a round cell morphology .
morphologically , the present case posed a diagnostic challenge by exhibiting proliferating compact spindle and round cells arranged in short fascicles with focal areas showing storiform pattern that was suggestive of spindle - cell sarcoma .
the spindle - shaped cells warrant distinction from other neoplasms with spindle - cell morphology .
special trichrome stains such as van gieson 's stain and masson 's trichrome stains were performed and supplemented by immunohistochemistry to eliminate the possibility of collagenous tumors .
immunohistochemically , the tumor cells were negative for the desmin , sma , s-100 and cd1a but strongly positive for lca and cd20 suggesting a spindle - cell variant of lymphoma .
hematolymphoid neoplasms with prominent spindle - cell features , also termed spindle - cell lymphoma , are rare but have been reported to occur in anaplastic large - cell lymphoma ,  reticulum cell sarcoma ,  primary bone lymphoma and primary soft tissue and/or skin lymphoma .
morphologically , these cases exhibit proliferation of spindle cells arranged in fascicles leading to a diagnosis of spindle - cell neoplasms of nonlymphoid origin .
the origin of spindle - cell b - cell lymphomas is uncertain , with previous investigators ( ferrara et al . , 2002 ;
lim et al . , 2008 ; yun 2009 ) reporting cases of spindle - cell b - cell lymphomas as variants of follicular lymphoma , whereas others ( wang et al . , 2010 ; kahlifa et al . , 2003 ; ries et al . , 2007 ;
2008 ) have classified them as a variant of diffuse large b - cell lymphoma .
while reporting three cases of primary b - cell malignant lymphoma in the maxilla with sarcomatous pattern noted that the spindle cells in these cases did not represent the malignant lymphoid cells , but rather they were a fibrotic stromal response as well as cytoskeleton alterations to the tumor which is seen particularly in tumor invasion of bone and soft tissue .
the present case however prominently displayed spindle - cell morphology amidst the lymphoid cell population ( as proven with immunohistochemistry too ) , rather than in the surrounding stromal cells .
cerroni ( 2002 ) , in a reported case series of cutaneous spindle - cell b - cell lymphoma , stated that spindled nuclei likely correspond to centrocytes and to a lesser extent centroblasts of follicular center cell origin , whereas somewhat larger and more monomorphous spindle cells are consistent with a spindle - cell variant of diffuse large b - cell lymphoma . a case of cutaneous spindle - cell b - cell lymphoma reported by goodlad , 2001 , exhibited immunohistochemical expression of cd10 and bcl-6 in addition to focal immunostaining of cd23 and cd35 for follicular dendritic cell networks within neoplastic follicles , prompting them to propose a follicular center cell origin .
reported five cases of spindle - cell b - cell lymphoma and based on immunohistochemical studies , genetic analysis and clinical presentation , categorized them as a variant of diffuse large b - cell lymphoma .
all five cases exhibited immunoreactivity for b - cell markers ( cd20 , cd79a ) and bcl-6 but were negative for t - cell markers ( cd3 and cd5 ) , cd10 and mum-1 .
furthermore , the finding of somatic immunoglobulin and bcl-6 mutations favor the origin of this lesion from b - cells in an early phase of intragerminal center maturation . in addition , all cases showed the absence of chromosomal translocation t ( 14;18 ) that is otherwise characteristic of follicular lymphoma .
( 2010 ) reported cases which showed positivity for sma and believed that the spindling probably results from aberrations in the cytoskeleton ; however , the tumor cells were negative for sma in the present case .
it has been hypothesized that cytokines such as tumor necrosis factor alpha , platelet - derived growth factor and transforming growth factor beta are produced by tumor cells which induce proliferation of fibroblasts in turn causing spindle - cell deformation within lymphoma cells .
the differential diagnosis of spindle - cell tumors does not normally include malignant lymphoma , a neoplasm that commonly has small round - cell morphology .
while the spindle - cell b - cell lymphoma has previously been commonly reported to occur within the skin , particularly of the head , neck and back regions , the current case illustrates that on rare occasions , the spindle variant of b - cell nhl may present in the mandible , an occurrence previously only reported by chi et al . , ( 2012 ) .
the prognosis of nhl depends mainly on the histology and the stage of the tumor ( whether it is localized or not , stage of evolution , number of extranodal localizations , etc . ) .
the location of the tumor ( e.g. presenting in the jaw ) is not found to be a significant prognostic factor as yet .
 a 64-year - old male farmer presented with a rapidly progressive swelling of the left mandible since 6 months . 
 the swelling was firm to hard , diffuse , nontender , obliterating the vestibule with paresthesia of lower lip . 
 the cone beam computed tomography imaging revealed an ill - defined , moth - eaten radiolucency with destruction of the buccal and lingual cortical plates . 
 the rapid growth and aggressive behavior of the lesion coupled with guidance from the patient 's previous reports from the incisional biopsy and fine needle aspiration cytology warranted a mandibular resection . 
 microscopic examination showed an encapsulated lesion situated in the connective tissue containing a mixture of proliferating spindle - shaped cells arranged in fascicles and round cells infiltrating into the connective tissue stroma and bone . 
 the neoplastic cells exhibited atypical features such as pleomorphism , hyperchromatism and increased mitotic figures with noncleaved nuclei . 
 a working diagnosis of a spindle - cell sarcoma was arrived at with various differentials provided such as fibrosarcoma , rhabdomyosarcoma , leiomyosarcoma , malignant peripheral nerve sheath tumor , langerhans cell histiocytosis and lymphoma and stating the need for immunohistochemistry to subtype the tumor . 
 the neoplastic cells were negative for van gieson 's stain and masson 's trichrome . 
 immunohistochemical analysis performed using desmin , smooth muscle actin , s-100 and cd1a in a bid to determine the phenotype of the tumor and rule out the previously stated differentials were all negative for the lesion . 
 lymphoid markers such as leukocyte common antigen and cd20 ( cluster differentiation marker for b - cells ) showed positivity in spindle - shaped cells as well as round cells indicating the tumor to be a lymphoproliferative lesion of b - cell type . a final diagnosis of  spindle - cell variant of non - hodgkin 's lymphoma  was rendered based on the immunohistochemical profile . 
INTRODUCTION
CASE REPORT
DISCUSSION
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