sebaceous carcinoma , first described by allaire in 1891 accounts for less than 1% of all cutaneous malignancies .
it is a rare but aggressive malignant neoplasm that arises from sebaceous glands with a tendency for both local recurrence and distant metastases .
we report a case of an extraocular type of sebaceous carcinoma of the scalp with no distant metastases .
a 65-year elderly man presented with a large asymptomatic swelling over the vertex of the scalp , which gradually progressed over a period of twelve months .
examination showed a large swelling of 15  12  5 cm size situated over the vertex of the scalp extending to the occipital and tempero - parietal regions.the tumor showed focal ulceration with yellowish malodorous seropurulent discharge [ figure 1 ] .
clinically , a differential diagnosis of cylindroma , angiosarcoma , deep fungal infections , nocardiosis , mycobacterial or atypical mycobacterial infections were considered .
a large multi- lobulated swelling with ill - defined margins and irregular surface showing focal ulceration and yellow sero - purulent discharge the culture of the seropurulent discharge revealed staphylococcus aureus and acinetobacter baumanni suggestive of secondary bacterial infection .
afb stain and culture for both mycobacteria and atypical mycobacteria and fungal culture were negative .
ct scan of the brain showed only age related cerebral atrophy , and there was no evidence of extension of the tumour or metastatic deposits .
histopathology revealed an infiltrating neoplasm in the dermis composed of cells arranged in lobules separated by fibrovascular stroma .
[ figure 2 ] neoplastic cells were round having moderate amount of eosinophilic to vacuolated cytoplasm and large nuclei with prominent eosinophilic nucleoli .
dermis showing a neoplasm composed of cells arranged in lobules separated by fibrovascular stroma ( h and e , 4 ) neoplastic cells having moderate amount of eosinophilic to vacuolated cytoplasm and large nuclei with prominent eosinophilic nucleoli and increased mitoses ( h and e , 40 ) immunohistochemical marker study showed diffuse strong positivity for cytokeratin and focal positivity for epithelial membrane antigen ( ema ) [ figure 4 ] .
sebaceous carcinoma is a rare malignant neoplasm , often occurs in adults with a slight male preponderance this malignancy can occur as peri - ocular and extraocular types and the former variant contributes to 75% of sebaceous neoplasms .
the upper eyelid is affected two to three times more often than the lower eyelid due to greater number of meibomian glands extraocular sebaceous carcinoma which constitutes 25% of the sebaceous neoplasms has been reported more commonly on the head and neck areas followed by trunk , salivary glands , genitalia , breast , ear canal , and the intra - oral cavity . the most frequent clinical presentation is a painless subcutaneous nodule but it can also present as pedunculated lesions , irregular mass or diffuse thickening of the skin .
this protean appearance frequently masquerades as other benign tumors or inflammatory conditions thereby leading to delay in diagnosis , inappropriate treatment , increased morbidity , and mortality .
the morphological hall mark of sebaceous differentiation is the detection of sebaceous cells and demonstration of fat in vacuolated tumor cells .
special stains such as oil red o may be helpful in confirming the presence of fat , but requires frozen section .
other differential diagnosis includes basal cell carcinoma with sebaceous differentiation for poorly differentiated sebaceous cell carcinoma .
our case did not show poorly differentiated basaloid cells and other features of basal cell carcinoma .
sebaceous carcinoma cells express immunohistochemical markers such as cytokeratin , epithelial membrane antigen ( ema ) , cam5.2 and anti - breast carcinoma associated antigen-225 antibody .
the current case showed diffuse strong cytokeratin expression and ema was focally positive in cells with sebaceous differentiation .
considering the morphological , histopathological and immunohistochemical marker study findings we favoured a diagnosis of sebaceous carcinoma .
the common associations of sebaceous carcinoma are muir - torre syndrome , an autosomal dominant condition comprising of sebaceous neoplasm with one or more low - grade visceral malignancies and nevus sebaceous of jadassohn .
distant metastases and recurrence rates are more common in the ocular type of sebaceous carcinoma when compared to extraocular sebaceous carcinoma as seen in our case .
recurrence rates of ocular sebaceous carcinoma ranges from 11% to 30% with distant metastases occurring in 3% to 25% though extraocular sebaceous carcinoma is less aggressive , a study with 91 cases of extraocular sebaceous carcinoma showed a recurrence rate of 29% with 21% developing metastases .
wide excision and selective use of radiotherapy is the ideal treatment of choice . in summary ,
this tumor should suggest the possibility of muir - torre syndrome and alert the clinician to search for occult malignancies .
 extra ocular sebaceous carcinoma is a rare malignancy when compared to peri ocular variant and these are derived from sebaceous gland epithelium . 
 the aggressive types of extra ocular sebaceous neoplasm are reported with lymph node and visceral metastasis associated with poor prognosis . here 
 we report a case of extensive cutaneous extra ocular sebaceous cell carcinoma confined to large area of scalp proven by immunohistochemistry without intra cranial involvement , distant metastases or evidence of muir - torre syndrome . 
INTRODUCTION
CASE REPORT
DISCUSSION