bacteria of the genus actinomyces are gram - positive bacilli which generally colonize mouth , colon and vagina . , if actinomycosis occurs , it often presents as an indolent , slowly progressive infection characterized by abscess formation , which can progress across tissue boundaries , can present with mass like features which simulate malignancy , can develop into a sinus tract and/or develop clinically into a refractory or relapsing infection after a short course of therapy . a 43-year old woman with no significant medical history presented with complaints of an unilateral slowly growing painful mass in the left breast . mammography ( fig . 1 ) and ultrasonography were conducted and showed a small abscess - like density retroareolarly.fig . . 1 mammography of the left breast showing a confined density in the retroareolar area . species identification was performed using matrix - assisted laser desorption ionization - time - of - flight mass spectrometry ( maldi - tof ms ; bruker ) . susceptibility testing for a. neuii was performed using e - tests ( biomerieux ) . at the time that culture findings became available , therefore , the cultured actinomyces was considered as skin commensals and a wait and see policy was installed . after several months , the patient returned to the outward clinic with complaints of pain in the breast . psychical examination of the breast showed mild erythema and ultrasonography showed a minimal increase of the lesion . the abscess was surgically drained and new purulent fluid from the abscess was sent to the laboratory . the material was processed as described above . in contrast to initial culture findings , determination by the maldi - tof ms showed peptostreptococcus magnus ( score value 2.056 ) . after four days there was also growth observed in the brewer thioglycollate medium . the isolate was shown to be susceptible to penicillin , amoxicillin , clindamycin , meropenem and vancomycin . histopathological examination of the obtained tissue showed abscess formation in an infection with a sinus tract . subsequently , the patient was treated for six weeks of intravenous penicillin followed by six months of oral amoxicillin successfully . secondly , a 73-year old woman with a history of bilateral breast cancer was seen at with severe pain and swelling of the left breast ten days after her ablation which was complicated by a large hamatoma treated conservatively . gram strain showed many leukocytes , some gram - positive cocci and many gram - positive rods . determination using maldi - tof ms identified a staphylococcus aureus after 2  days there were colonies visible on the anaerobically incubated schaedler agar . determination by the maldi - tof ms revealed an a. neuii susceptibility testing was performed using e - tests . unfortunately , patient returned four days after discharge with a relapse of the hematoma which was surgically evacuated . a month later at the outward clinic she showed full recovery.fig . other isolates that have been identified as pathogens causing primary breast actinomycosis include actinomyces viscosus , actinomyces turincensis and actinomyces radingae 
 . it differs from the other actinomyces species because of its aerobic growth and its microscopic morphology without branching . we were able to retrieve only three former cases of a. neuii causing primary actinomycosis . in the first case , treatment with antibacterials was unsuccessful and the lesion had to be surgically removed . in the second case , patient was successfully treated with amoxicillin for 21  days . in the third case , actinomycosis , regardless of species , should be treated with high doses of antibacterials for a prolonged period of time although therapy needs to be individualized . current guidelines recommend high dose of penicillin intravenously for two to six weeks , followed by oral therapy with penicillin or amoxicillin for 6 to 12 months . alternative antibacterial treatments include doxycycline , erythromycin or clindamycin . if actinomycosis presents with well - defined abscess then surgical drainage followed by long - term antibacterial therapy is indicated . we describe this combination of treatment in our cases . in the first case initial cultures showed islolated a. neuii . because signs of infection had decreased this finding was interpreted as skin flora and not as a pathogen . therefore medical treatment was considered unnecessary . in retrospect , if antibacterial therapy had been given at first presentation recurrence of the infection might have been prevented . actinomyces species morphologically resemble diphtheroids and could be dismissed as skin commensals , even when isolated from an abscess sample . in both of our presented cases we found different organisms in the culture additional to a. neuii . in the first case we found p. magnus and in the second case s. aureus was present . although a. neuii infection is known for its chronicity , the influence of these mixed organisms on the severity of infections remains unclear . further research on the effect of mixed organism on the severity of an a. neuii infection is required .
actinomycosis is a slowly progressive infection caused by anaerobic bacteria , primarily from the genus actinomyces . 
 primary actinomycosis of the breast is rare and presents as a mass like density which can mimic malignancy . 
 mammography , ultrasonography and histopathologic examination is required for diagnosis . 
 treatment should consist of high doses of antibacterials for a prolonged period of time and possibly surgical drainage . 
 primary actinomycosis infections are commonly caused by a. israelii . 
 actinomyces neuii is a less common cause of classical actinomycosis . 
 we present two cases of primary actinomycosis of the breast in two female patients caused by a. neuii .