extraocular sites for these tumours account for only about a quarter of the cases and usually include the skin of the head and neck region . they can also occur on the trunk , extremities , genitalia and rare sites like lungs , salivary glands , breast . the morphologic diversity of these tumours , especially in unusual sites , makes their distinction from more common primary tumours of those organs a difficult task . it is important to identify them accurately , as they have a high incidence of recurrence and association with regional nodal metastasis . we report a series of sebaceous carcinomas occurring at extraocular , extra - head and neck sites . these cases are presented for their rarity , histopathologic spectrum and difficulty encountered in diagnosis . a 44-year - old man presented with skin nodules on the arm and anterior chest wall three years ago . the lesions ranged in size from 1 to 2.5 cm in diameter . on excision , the lesions were cystic and filled with purulent material , justifying the clinical impression of epidermal cyst . the cells were crowded with scant cytoplasm and admixed with cells showing multivacuolated appearance and scalloped nuclei , characteristic of sebocytic differentiation ( figure 2b ) . the patient had multiple recurrences of similar lesions on the thigh and back during a two - year follow - up . the patient is currently asymptomatic . a 48-year - old man presented to the fnac ( fine needle aspiration cytology ) clinic of our hospital one year ago with a nodular axillary mass measuring around 5  4 cm . the axillary skin was puckered and the mass was palpable ( figures 2a , 2b ) . fine needle aspiration of the mass showed a neoplasm with plasmacytoid morphology ( figure 2c ) . immunohistochemistry was done for cytokeratin ( ck ) 7 , ck 20 , hmb-45 , s-100 , psa ( prostate specific antigen ) and ttf-1 ( thyroid transcription factor ) , all of which were negative . the tumour cells were positive for ck , ema ( epithelial membrane antigen ) and focally for cd 15 . ema staining showed a bubbly , vacuolated cytoplasm in many cells , highlighting their sebocytic nature ( figure 3d ) . this was followed by a wide excision of the axillary mass with regional lymph node dissection . there were varying architectural patterns , such as solid nests ( figure 3a ) , areas with comedo - necrosis ( figure 3b ) , and thick cords with hyalinisation ( figure 3c ) . the postoperative period was uneventful and the patient is currently free of disease . a 78-year - old lady presented to the fnac clinic of our hospital with history of erythematous nodular and plaque - like lesions measuring 6  4 cm on the right anterior chest wall ( figure 4a ) . fine needle aspiration from the nodule showed a poorly differentiated carcinoma ( figure 4b ) . a tumour was seen in the dermis with the characteristic morphology of sebaceous carcinoma ( figure 4c ) and a prominent pagetoid spread ( figure 4d ) . a 44-year - old man presented with skin nodules on the arm and anterior chest wall three years ago . the lesions ranged in size from 1 to 2.5 cm in diameter . on excision , the lesions were cystic and filled with purulent material , justifying the clinical impression of epidermal cyst . the cells were crowded with scant cytoplasm and admixed with cells showing multivacuolated appearance and scalloped nuclei , characteristic of sebocytic differentiation ( figure 2b ) . the patient had multiple recurrences of similar lesions on the thigh and back during a two - year follow - up . a 48-year - old man presented to the fnac ( fine needle aspiration cytology ) clinic of our hospital one year ago with a nodular axillary mass measuring around 5  4 cm . the axillary skin was puckered and the mass was palpable ( figures 2a , 2b ) . fine needle aspiration of the mass showed a neoplasm with plasmacytoid morphology ( figure 2c ) . immunohistochemistry was done for cytokeratin ( ck ) 7 , ck 20 , hmb-45 , s-100 , psa ( prostate specific antigen ) and ttf-1 ( thyroid transcription factor ) , all of which were negative . the tumour cells were positive for ck , ema ( epithelial membrane antigen ) and focally for cd 15 . ema staining showed a bubbly , vacuolated cytoplasm in many cells , highlighting their sebocytic nature ( figure 3d ) . this was followed by a wide excision of the axillary mass with regional lymph node dissection . there were varying architectural patterns , such as solid nests ( figure 3a ) , areas with comedo - necrosis ( figure 3b ) , and thick cords with hyalinisation ( figure 3c ) . a 78-year - old lady presented to the fnac clinic of our hospital with history of erythematous nodular and plaque - like lesions measuring 6  4 cm on the right anterior chest wall ( figure 4a ) . fine needle aspiration from the nodule showed a poorly differentiated carcinoma ( figure 4b ) . a tumour was seen in the dermis with the characteristic morphology of sebaceous carcinoma ( figure 4c ) and a prominent pagetoid spread ( figure 4d ) . wide local excision with removal of regional nodes is the mode of treatment . around 2025% of cases these variably atypical polygonal tumour cells are usually arranged as dermal nodules with a fibrovascular stroma that does nt exhibit much desmoplasia . however , these classical features may be subtle or even absent in a few cases . a varied morphologic spectrum has been described for these tumours , like basaloid , squamoid , organoid , pseudo - neuroendocrine , etc . this diversity may be explained by the common embryologic origin of the folliculo - sebaceous - apocrine unit being recapitulated in their neoplasms , as well . these tumours are known to be great mimics of different types of neoplasms , which often makes the right diagnosis a challenge . this was demonstrated in our second case in which the tumour showed a range of cytoarchitectural features and rendered the diagnosis difficult . the vacuolated cytoplasm accentuated by the ema stain is a typical feature of sebaceous carcinomas , along with positivity for pancytokeratin , cd 15 and ca 15.3 . the site of the tumour in the second case was also more in favour of a breast primary than other neoplasms . ductal carcinoma of the breast shows a positive stain for ck-7 , unlike our case . it should be noted that primary sebaceous carcinoma of the breast is extremely rare in comparison to an extraocular sebaceous carcinoma arising from the skin . a few cases of a sebaceous carcinoma of the breast have been reported in patients having mts . very rarely , a myoepithelial neoplasm of the breast may also show varied patterns like clear cells and a plasmacytoid morphology . however , one needs to consider the overall morphology , presence of spindle cells , mitotic activity and myoepithelial markers , if necessary , to make the distinction . a metastatic tumour from other sites also needs to be ruled out in such cases , for which immunostains are very useful . it is characterised by the occurrence of sebaceous gland neoplasms and/or keratoacanthomas in association with a visceral malignancy , commonly of the gastrointestinal or the genitourinary tract [ 912 ] . genetically , these tumours are characteristed by mutations in the mismatch repair gene products , especially msh-2 . cystic differentiation is an important histologic clue to its association with mts , as seen in our case . such patients need to be screened for a concomitant gi malignancy and followed up closely . this is considered to be a  field effect  rather than being direct precursor of or extensions from an underlying sebaceous carcinoma . an exclusively in - situ component may rarely occur and differentiating this from an in - situ squamous carcinoma may be extremely difficult , especially if sebocytic differentiation is sparse . the morphologic variations that can be encountered along with occurrence at unusual sites can render extraocular sebaceous carcinomas elusive to the pathologist . a high index of suspicion and a careful search for sebocytic differentiation are the key features . ema immunostain is a useful adjunct in doubtful cases , as it highlights the multivacuolated cytoplasm . the pathologist needs to be cognisant of the histopathologic gamut of sebaceous carcinomas to avoid misdiagnosis .
background : extraocular sebaceous carcinomas are rare cutaneous malignancies that account for only about 25% of all sebaceous carcinomas . 
 the most common site of occurrence is the head / neck region . 
 they are aggressive neoplasms that possess metastatic potential to regional or distant sites . wide local excision of the lesion with removal of regional lymph nodes is the usual mode of therapy.methods:we present a series of three cases of sebaceous carcinomas occurring in extraocular sites outside the head and neck areas , like the axilla , chest wall , arm and thigh . 
 one of these cases had an associated colonic carcinoma and constituted muir - torre syndrome ( mts ) . 
 another case presented with a skin nodule and regional nodal metastasis . 
 the third case had a history of recurrent similar lesions at the same site.conclusion:although rare , extraocular sebaceous carcinomas are seen at varied sites and frequently pose problems in diagnosis . 
 a longterm follow - up of these cases is warranted due to their aggressive behaviour , risks of recurrence , metastasis and the possibility of development of visceral malignancies .