polyarteritis nodosa ( pan ) is a necrotizing vasculitis of the small and medium - sized arteries . kussmaul and maier first described the disease in 1866 when they reported a case of necrotizing arteritis . pan of the testis is a rare pathologic entity that at imaging can erroneously be interpreted as tumour . a 28-year - old white man presented with a seven - day history of left testicular pain . prior to the present hospitalisation , the patient was treated with antibiotics by his general practitioner for presumed epididymitis . a scrotal ultrasound confirmed a hypoechogenic mass in the lower pole of the left testis . mri confirmed an area of heterogeneous parenchyma in the lower pole of the left testis , without invasion in the tunica albuginea . 1 ) . complete blood count , blood urea nitrogen , creatinine , liver function tests and hepatitis b surface antigen were normal . testicular tumour markers were negative : beta human chorionic gonadotropin level was less than 1.0 u l ( normal 0.05.0 ) , alpha - fetoprotein level was 6 g l ( normal 020 ) . c - reactive protein ( crp ) was slightly elevated to 14.4 mg l. 
 figure 1 
 axial t2-weighted images of the scrotum . an ill - marginated hypointense area is seen in the lower pole of the left testis . an ill - marginated hypointense area is seen in the lower pole of the left testis . two years earlier , he had been treated for a venous thrombo - embolism of the right lower limb . lab results at that time showed a reactive thrombocytosis . in order to rule out an underlying tumour , two years post - nephrectomy , the patient was investigated for recurrent cutaneous and subcutaneous painful nodules at the lower limbs . these lesions were thought to be superficial thrombophlebitis . because of a history of renal cell carcinoma , it was presumed that an abnormal coagulation tendency occurred as a paraneoplastic phenomenon . however , a ct scan of the abdomen and thorax , and an onco - pet scan failed to show distant metastases or local recurrence . medium - sized artery in the tunica albuginea with segmental transmural necrotizing inflammation of the vessel wall and thrombotic occlusion of the lumen . ( b ) artery affected by polyarteritis nodosa at a later stage with partly destroyed wall and occlusion of the lumen by a fibroblastic proliferation and marked surrounding mononuclear inflammatory infiltrate . ( c ) detail of the fibroblastic proliferation in the lumen of an occluded artery with formation of new capillar lumina surrounded by an inflammatory infiltrate . medium - sized artery in the tunica albuginea with segmental transmural necrotizing inflammation of the vessel wall and thrombotic occlusion of the lumen . ( b ) artery affected by polyarteritis nodosa at a later stage with partly destroyed wall and occlusion of the lumen by a fibroblastic proliferation and marked surrounding mononuclear inflammatory infiltrate . note the beginning fibrinoid necrosis , as usually seen in a still later stage . ( c ) detail of the fibroblastic proliferation in the lumen of an occluded artery with formation of new capillar lumina surrounded by an inflammatory infiltrate . testicular pathology as a presenting symptom of vasculitis is exceptional . in most cases , testicular vasculitis occurs as a part of a systemic disease , most frequently pan . this is an uncommon disease of unknown origin with an annual incidence of 0.7/100.000 . in its classical form , the testis is involved in about 3886% of all cases , but only 18% are symptomatic . whilst common , testicular involvement is rarely the presenting manifestation . most often , systemic features of fever , malaise , weight loss and diffuse aching will be the first symptoms . they can present along with symptoms of multisystem involvement such as skin rash , asymmetric polyartritis and peripheral neuropathy . laboratory tests are mostly non - specific ; they reflect the systemic inflammatory nature of the disease . only a few case reports describe a painful testicular mass as the first symptom of pan . in 1971 , mowad et al . described a 31-year - old patient presenting with a mass in the testis associated with multiple skin and subcutaneous nodules consistent with the diagnosis of pan . in 1983 , lee et al . described a 25-year - old patient who presented with bilateral testicular pain associated with paraesthesia in the distribution of the left lateral peroneal nerve and laboratory evidence of systemic pan . described a 28-year - old man who presented with progressive pain and enlargement of the right testis . another case of isolated pan of the testis in a 29-year - old man was described by persellin et al . associated systemic symptoms ( spiking temperatures to 40 c , elevated erythrocyte sedimentation rate up to 120 mm per hour and anaemia ) were noted . reported a 19-year - old patient who presented with a painful mass in the testis , suspect for tumour . associated , crp was moderately elevated and the patient developed similar complaints in the contralateral testis , suggestive of systemic involvement . in 1995 , mukamel et al . reported 2 cases , a 28-year - old and a 35-year - old male , presenting with discomfort and swelling of the testis . the most recent case was presented by eilber et al . in 2001 . a 43-year - old white man presented with a testicular mass and associated systemic complaints of fever , myalgia and gross hematuria . esr was 74 mm h. diagnosis of pan was made through radical orchidectomy . in the presented patient , this was thought to be a paraneoplastic phenomenon after radical nephrectomy for a conventional type renal cell carcinoma 2 years earlier . after the diagnosis of pan was made on the orchidectomy specimen , the cutaneous lesions were finally recognized as cutaneous pan . with this knowledge , a simple testicular biopsy would probably have avoided a radical orchidectomy . testicular biopsy is a simple procedure that can be performed under local anaesthesia with minimal morbidity . the prognosis of untreated systemic polyarteritis nodosa is poor and the 5-year survival is less than 13% . if the disease is treated with immunosuppressive drugs ( corticoids and cyclophosphamide ) the 5-year survival rises from 13 to 82% . vasculitis or pan of the testis should be considered in the differential diagnosis when a patient presents with an acute , painful mass in the testis , without obvious trauma or epididymitis and when a tumour is suspected on ultrasound or mri .
a 28-year - old man presented with a seven - day history of testicular pain . physical examination revealed a mass in the lower pole of the left testis . 
 this mass was a tumour suspect on scrotal ultrasound and mri . 
 testicular tumour markers were negative . 
 a radical orchidectomy was performed . 
 histologically , the diagnosis of polyarteritis nodosa ( pan ) was made . 
 retrospectively , the diagnosis of pan could have been made earlier . 
 the patient was treated for superficial thrombophlebitis in the months prior to admission . 
 this was considered to be a paraneoplastic phenomenon after radical nephrectomy for a conventional type renal cell carcinoma two years earlier . 
 after the diagnosis of pan was made on the orchidectomy specimen , the cutaneous lesions were finally recognized as cutaneous pan . with this knowledge , a simple testicular biopsy could have avoided a radical orchidectomy . 
 a short review of literature on testicular pan is given .