in ano - rectum different types of neoplastic as well non - neoplastic lesions can occur . among the latter , hemorrhoids , anal fissure or polyps are common . this is a report of an anal growth , which was clinically diagnosed as thrombosed pile but histopathology and immunohistochemistry revealed its real nature . a 60-year - old male presented to surgical out - patients department complaints of bleeding from rectum and pain during defecation . he reported a history of weight loss and anorexia , and at examination he was pale and cachectic . on rectal examination a growth about 321 cm was found in the rectum , 4.3 cm from the anal verge . the clinical diagnosis was of a thrombosed pile , therefore it was excised and sent for histopathological examination . the examination at the microscopy revealed a tumor replacing the entire wall thickness with ulceration of overlying epithelium . the tumor cells were disposed in fascicles and sheets ( figure 1a ) and were spindle - shaped . few of them showed prominent inclusion like nucleoli and atypical mitotic figures , while many contained blackish pigment ( figure 1b ) . the tumour cells were strongly positive for s-100 and hmb-45 ( figure 1d ) . based on these findings a diagnosis of sarcomatous variant of malignant melanoma figure 1microphotograph of the tumor in the ano - rectum showing ( a ) the tumor cells arranged in long parallel running fascicles ( b ) the high - power view of individual cells with prominent spindling and abundant blackish pigment in many of them ( c ) schmorl 's stain demonstrating the pigment to be melanin stained as blue green granules and ( d ) strong positivity for hmb-45 in the tumor tissue . microphotograph of the tumor in the ano - rectum showing ( a ) the tumor cells arranged in long parallel running fascicles ( b ) the high - power view of individual cells with prominent spindling and abundant blackish pigment in many of them ( c ) schmorl 's stain demonstrating the pigment to be melanin stained as blue green granules and ( d ) strong positivity for hmb-45 in the tumor tissue . thereafter , an abdomino - perineal resection with removal of bilateral inguinal , pelvic and mesorectal lymph nodes was carried out . on histological examination no residual tumor was identified at the primary site , however one of the inguinal lymph nodes was found to harbor the metastatic tumor deposits . the patient received radiation and chemotherapy and was then discharged and advised for a regular follow - up . the patient however came back after 13 months and on computerized tomography ( ct ) scan of abdomen showed multiple secondaries in liver . the patient was discharged on his own request and thereafter no follow up could be obtained . malignant melanoma is a rare neoplasm in the ano - rectum accounting for only 13% of all tumors . most of the malignant melanomas are of classical type and the sarcomatous variant , although it is well known in skin has been rarely reported at this site . by reporting this case we intended to alert clinicians and pathologist about its occurrence and importance of its recognition . a dermal sarcomatoid melanoma has even worse prognosis than classical malignant melanoma with a 5-year survival rate accounting to only 15% , despite an aggressive , multimodality approach . it has been reported that 38% of patients have already metastatic disease at the time of diagnosis . however , its prognosis in ano - rectum is not yet clear due to its rarity at this site . the present case also showed a dismal prognosis , as patient developed disseminated malignancy despite aggressive therapy . further data on the various prognostic factors is needed , which is possible only if more cases are reported . its diagnosis also may be difficult even on histology and it may be confused with other more common spindle cell tumors i.e. leiomyoma , haemangioma , haemangiopericytoma , neurilemmoma , neurofibroma , granular cell tumor , spindle cell lipoma , gastrointestinal stromal tumor , malignant fibrous histiocytoma , leiomyosarcoma , rhabdomyosarcoma , fibrosarcoma and spindle cell carcinoma . the key diagnostic feature is the melanin production , which may be absent in approximately 20% of the cases . in such difficult cases only immunostaining can help in achieving the correct diagnosis . a sarcomatous melanoma in ano - rectum is seldom reported in the literature and the present case highlights several key points . most importantly , when faced with a spindle cell lesion of anal canal , especially in an elderly , the diagnosis of sarcomatous melanoma must be included in the differential . as occurred in our case , the clinical impression is often misleading , therefore it is important that the pathologist maintain a high index of suspicion . the histologic appearance of sarcomatous melanoma mimics other spindle cell tumors , therefore immunohistochemical stains play an important role in diagnosis . since present therapeutic strategies may not necessarily alter the prognosis , an early recognition of this unusual variant of malignant melanoma is a key to prolong the survival .
we report a case of extremely rare variant of ano - rectum malignant tumor . the tumor is often misdiagnosed as either hemorrhoids or rectal polyp , which are benign diseases . on histology also this variant 
 may be confused with other more commonly occurring spindle cell lesions in this area ; its recognition is therefore important as it normally has a poor prognosis .