malignant melanoma of the skin although common , can mimic a wide variety of lesions clinically.amelanotic melanoma is a variant of melanoma , which is diagnosed only after a complete work - up , which includes histopathology and ihc . malignant melanoma of the skin although common , can mimic a wide variety of lesions clinically . amelanotic melanoma is a variant of melanoma , which is diagnosed only after a complete work - up , which includes histopathology and ihc . melanomas , mainly of the skin are common tumors , but the incidence of amelanotic melanomas has been estimated to be between 1.8% and 8.1% of all melanomas . amelanotic malignant melanoma is a subtype of cutaneous malignant melanoma that has little or no pigment on visual inspection , as a result of which it can masquerade as a variety of other benign and malignant skin conditions . herein we present a similar case , in a 73-year - old lady , presenting as a soft - tissue mass with the final diagnosis being reached only after marker studies . a 73-year - old lady , farmer by occupation , presented to the surgical out - patient department with a large ulcerative nodular mass of 3 months duration , in the flexor aspect of the right hand , above the elbow joint , rapidly increasing in size , ulcerated since 2 weeks [ figure 1 ] . ulcero - nodular growth on the postero  medial aspect of the right upper arm fine needle aspiration was carried out a diagnosis of poorly differentiated round cell tumor was made on cytology [ figure 2 ] . pap stain of fine needle aspiration cytology  cellular smears with sheets of discohesive round cells magnetic resonance imaging showed a soft - tissue mass in the right arm , involving the skin and subcutaneous soft - tissue measuring 7 cm  6 cm  5 cm , ulnar nerve sandwiched between the mass and triceps , with no definite infiltration . mitotic activity was high ( 2 - 3/hpf ) , with areas of necrosis seen . a diagnosis of poorly differentiated round cell tumor was made [ figure 4a  c ] and the patient got discharged against medical advice . cut section showing a grey white tumor measuring 7 cm  5 cm  4 cm , with hemorrhage ( h and e , 10 ) showing the tumor with ulcerated overlying skin ( h and e , 10 ) showing the undifferentiated tumor cells in sheets without any definite arrangement h and e stain showing individual round tumor cells with mitotic figure ( arrow ) and occasional prominent nucleoli to further categorize the tumor immunohistochemistry ( ihc ) markers were used comprising pan cytokeratin ( ck ) , cd45 , s-100 , cd99 , epithelial membrane antigen , cd34 , b - cell lymphoma-2 ( bcl-2 ) , ck7 , ck19 , human melanoma black-45 ( hmb-45 ) and cd56 . the tumor cells were positive focally for cd99 , focally for s-100 and strongly positive for hmb-45 . a final diagnosis of amelanotic melanoma was made , with a clark 's grading of v and breslow 's thickness of 1.5 mm . the patient was contacted to come for further management repeatedly , but has not turned up until date . malignant melanomas most commonly occur on skin ( over 90% ) and less commonly on mucosal surfaces ( slightly over 1% ) . it accounts for approximately 4% of all skin cancers , but is responsible for 79% of all skin cancer related deaths . amelanotic melanoma usually occurs in sun - exposed skin of elderly with photo damage , simulating various skin lesions . but the tumor size in our patient is one of the largest on presentation , as per pubmed / medline search . cytologically , a high cell yield with a predominant population of dissociated cells , showing nuclear pleomorphism , prominent nucleoli and increased mitotic activity can be seen . however , diagnosis of the amelanotic variant on cytology is challenging because in the absence of pigment , the tumor cells mimic those of carcinoma or sarcoma , like in our case . even on histopathology melanoma has attained diagnostic notoriety for its capacity for histomorphological diversity and ability to masquerade as a number of non - melanocytic neoplasms , especially true for the amelanotic variety . histopathological examination alone , as in our case can leave the pathologist with an extensive list of differential diagnoses as mentioned in table 1 . as each of the tumors express characteristic patterns of markers , ihc is often essential in the formulation of a definitive diagnosis . histopathological differentials to be considered for superficial small round cell tumors with a provisional diagnosis on histopathology as poorly differentiated round cell tumor , which comprise sarcomas , carcinomas , melanomas and lymphomas we ran the initial panel of markers  pan ck , cd45 and s-100 . the next panel comprised of desmin , vimentin , cd34 , ck7 , bcl-2 and cd99 . focal staining for bcl-2 was seen , which still ruled out synovial sarcomas and lymphomas as ck7 and cd45 were negative cd99 was focally positive , but as s-100 was also positive possibilities of primitive neuroectodermal tumor and ewing 's were ruled out . a strong positivity for hmb-45 was seen , this along with s-100 positivity [ figure 5a  c ] , absence of pigment on masson 's fontana stain and histomorphology helped us to a diagnosis of amelanotic melanoma , similar to studies of limketkai b et al , roy et al . and oguri et al . strong positivity for s-100 strong positivity for hmb-45 a review of our slides did not reveal a few features typical of a melanoma such as pigment , junctional activity , grooves and pseudo inclusions , but cells showing prominent nucleoli , high mitotic activity , infiltration into the surrounding tissues was seen . many hypothesis have been proposed to explain the lack of pigment in amelanotic melanoma such as lack of tyrosinase , agenesis of melanosomes , undetectable levels of melanin production or abnormal melanogenesis . a study of 36 cases of amelanotic melanoma by gualandri et al . concluded that amelanotic melanomas have an intrinsic faster speed of growth , worse prognosis , with breslow 's thickness being the most important determinant factor . treatment of melanoma , including the amelanotic variant is wide surgical excision in combination with chemotherapy and to a lesser extent immunotherapy and radiation , with a check on nodal status . the aim of this presentation is to highlight on the fact that when a diagnosis of poorly differentiated round cell tumor is made , possibility of amelanotic melanoma must also be kept in mind , with one melanotic marker being included in the ihc panel , thereby preventing diagnostic delay and aiding in better patient management . amelanotic melanoma must be considered as one of the differentials in cases show in histopathological features of a superficial poorly differentiated small round cell tumor.one melanotic marker must be included in the ihc panel , to rule out amelanotic melanoma , thereby preventing diagnostic delay and aiding in better patient management . amelanotic melanoma must be considered as one of the differentials in cases show in histopathological features of a superficial poorly differentiated small round cell tumor . one melanotic marker must be included in the ihc panel , to rule out amelanotic melanoma , thereby preventing diagnostic delay and aiding in better patient management .
malignant melanoma poses a remarkable capacity for morphological diversity and often presents as a diagnostic challenge due to its wide clinical presentation . 
 we present a case of a 73-year - old lady , with a large superficial ulcerative nodular mass on the flexor aspect of the right upper arm . on fine needle aspiration 
 poorly differentiated round cell tumor was suggested , with histopathology also supporting the same diagnosis . 
 a final diagnosis of amelanotic melanoma was given following immunohistochemical work - up using a panel of relevant markers . 
 we are presenting this case , not only for its rare clinical presentation , but also for the diagnostic difficulties encountered by us in cytology and histopathology to reach the final diagnosis .