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 . 