it is an aggressive tumor that most metastasizes to regional lymph nodes and distant viscera ; surgery with safe margins is the mainstay of treatment . we report a case of 68-year - old woman who presented with an invasive clear cell hidradenocarcinoma situated in the left parotid area which recurred 5 months after surgery , this recurrence was managed successfully by high - dose irradiation of the tumor bed ( 66 gy ) and regional lymphatic chains ( 50 gy ) , after a follow - up of more than 15 months , the patient is in good local control without significant toxicity . post operative radiotherapy allows better local control and should be mandatory when histological features predictive of recurrence are present : positive margins , histology poorly differentiated , perineural invasion , vascular and lymphatic invasion , lymph node involvement , and extracapsular spread . hidradenocarcinoma ( hdc ) is a rare malignancy which arises from sweat glands , and it occurs conventionally de novo and rarely results in degeneration of a pre - existing hidradenoma , and wide surgery is the mainstay of treatment . the estimated recurrence rate is 50% despite aggressive surgical treatment , this justifies the use of an adjuvant treatment , based on external beam radiotherapy . a 68 year - old - woman presented with a lump in the parotid area measuring 1,5 cm in size , which progressed slowly over the next 2 years before treatment . surgical excision was performed , pathologically this was a malignant clear cell hidradenocarcinoma with positive surgical margins , and re - excision of tumor bed was performed without leaving residual tumor . lesion recurred five months later , ct scan showed a tumor of parotid area measuring 3.6 cm and infiltrating overlying skin ( fig . subtotal parotidectomy has been realized 4 months later , surgical margins were positive with great residual tumor measuring 7 cm , associated with ipsilateral fixed adenopathy measuring over 6 cm in size . external beam radiotherapy has been realized , with opposed pair of large lateral opposing faciocervical fields that cover primary tumor bed , ipsilateral adenopathy and the upper neck lymphatics in one volume , at a total dose of 66 gy , 2 gy per fraction , 5 fractions a week , 33 fractions ( fig . lower neck lymphatics received prophylactic dose of 50 gy , with an anteroposterior ipsilateral supraclavicular matched field . after a follow - up of more than 15 months the patient is in good local control without significant toxicity ( fig . hdc has been described for the first time by keasby and hadley in 1954 , even today fifty cases have been reported in the literature . it is a rare tumor reported most frequently on the head and neck and rarely on the distal extremities ; the mean age of onset is 50 years , with a slight female predominance . hdc can derive from preexisting clear cell hidradenomas but more commonly appear de novo , with the molecular events responsible for the pathogenesis currently unknown . hdc usually present as a nodule , painless , firm or cystic , sometimes leaving a liquid which is serous or hemorrhagic . the diagnosis is based on histopathological examination after biopsy or surgery , showing sweat intradermal proliferation inside a dense hyalinized stroma with nuclear pleomorphism and figures of mitosis , necrosis is common . surgery is the cornerstone of treatment , consisting of wide excision ensuring negativity of margins[6710 ] , the role of lymph node dissection is only discussed in the literature with anecdotal report . in the absence of known distant metastases , clinically involved nodal regions should be dissected and irradiated , while clinically uninvolved primary nodal drainage areas should be either dissected or irradiated[6710 ] . the role of a selective neck dissection is still debated and there is no clear evidence to its usefulness . certain histopathology criteria should encourage consideration of postexcisional radiotherapy , the features , such as dermal lymphatic invasion , nerve - sheath involvement , deep structure infiltration , positive resection margins , highly anaplasic morphology , and extracapsular lymph node extension , may identify a high risk of recurrence . harari and colleagues reported complete remissions after external beam radiotherapy for sweat gland tumors with positive margins after surgery , the dose and technique of radiotherapy are not consensual . in the work of harari et al , primary surgical beds were treated with 70 gy , using a combination of photons and electrons , and regional lymphatic chains with 50 gy . there are both acute and long - term sequelae of radiation therapy for head and neck cancer that occur because of effects on normal tissues . some common adverse effects include mucositis , xerostomia , trismus , hearing loss , and facial nerve dysfunction . severe late complications include the risk of soft tissue necrosis , osteoradionecrosis , orocutaneous fistula , blindness , and second malignancies . with the advent of new techniques of radiotherapy , such side effects are less frequent and better tolerated . it seems obvious that the natural history of this aggressive tumor characterized by local recurrences mandates the use of radiotherapy after surgery for better local control .
context : clear cell hidradenocarcinoma is a rare carcinoma arising from sweat glands . it is an aggressive tumor that most metastasizes to regional lymph nodes and distant viscera ; surgery with safe margins is the mainstay of treatment.case report : we report a case of 68-year - old woman who presented with an invasive clear cell hidradenocarcinoma situated in the left parotid area which recurred 5 months after surgery , this recurrence was managed successfully by high - dose irradiation of the tumor bed ( 66 gy ) and regional lymphatic chains ( 50 gy ) , after a follow - up of more than 15 months , the patient is in good local control without significant toxicity.conclusion:post operative radiotherapy allows better local control and should be mandatory when histological features predictive of recurrence are present : positive margins , histology poorly differentiated , perineural invasion , vascular and lymphatic invasion , lymph node involvement , and extracapsular spread .