A 31-year-old female with tender lump in left breast lump 4 months with pain and intermittent yellow colored nipple discharge (2 months) [Figure 1a]. Fine-needle aspiration yielded 10 ml of yellowish pus like material with cytological findings shown in [Figure 1b , c, and c (inset)].
What is the diagnosis based on cytomorphology?
 Actinomyces 
Tuberculosis
Non-Hodgkin's lymphoma
Ductal carcinoma.
 Answer to the first question: 
1. a. Actinomyces
What is the special stain used in such cases?
PAS
ZN
Gram
All of the above
None of the above.
What is the most common causative agent of breast abscess?
Staphylococcus
Streptococcus
Enterococcus
Pseudomonas.
Actinomycosis is a chronic infection caused by Actinomyces species characterized by abscess formation, tissue fibrosis, and draining sinuses. The spectrum of infections caused by Actinomyces species ranges from classical invasive actinomycosis to a less invasive form of superficial skin and soft-tissue infection. It is an often relapsing granulomatous infection that characteristically crosses tissue planes and forms abscesses and sinus tracts. First described by Ammentrop in 1893, primary actinomycosis of the breast is very rare and most commonly caused by Actinomyces israelii which normally inhabits the mouth, colon, and vagina.
Breast actinomycosis is primary when inoculation occurs through the nipple. Secondary actinomycosis of the breast refers to the extension of a pulmonary infection through the thoracic cage in a process that can affect the ribs, muscles, and finally the breast.[] Primary actinomycosis infections are commonly caused by A. israelii. Actinomyces neuii is a less common cause of classical actinomycosis. Actinomyces of breast is an uncommon occurrence with very limited case reports in the literature. Most often, the diagnosis of Actinomyces breast is made based on cytological findings. Differentiating causative agents of breast abscess is challenging. Knowledge of this organism at this rare site is essential so that it could be considered in the differentials. Distinguishing breast actinomycosis from tuberculosis and other potential infectious conditions is possible through pathological examination.[] Cytomorphology helps in making the diagnosis. Microbiological examination aids in the confirmation of the same. Although breast is a rare site for Actinomyces infection, cytopathologists must be aware of its occurrence and consider this in their differentials while diagnosing breast lumps.
 Answers to the additional questions: 
2. c. Gram
3. a. Staphylococcus.