1. References:1. Georgiannos SN, et al/.Secondary neoplasms of the breast: a survey of the 20 th Century. Cancer 2001: 92 (9):2259-2266. Case Presentation: A 78 year old Caucasian female was admitted to the Respiratory Ward with progressive dyspnoea, confusion and non productive cough. Her medical history included hypothyroidism and schizophrenia. She lived alone and did not smoke. She was commenced on IV Tazocin 4.5g tds. Table 1. Current Medications. Respiratory Examination:  Decreased air entry bilaterally. Respiratory rate 26. Sp02 96% 2L.  3x2cm mass in the upper outer quadrant of her left breast. No axillary lymphadenopathy evident. Cardiovascualr Examination:  HR 98, BP 122/77 mmHg, HS I + II + 0. Inves tigations:  Haematological, ABGs, MSU, blood cultures  Chest radiograph, CTPA, bronchoscopy  Ultrasound and Mammogram of left breast  CT thorax, abdomen, pelvis with contrast Fig.1 Chest Radiograph Fig.2 CTPA: no pulmonary embolus A large soft tissue mass in the right lower lobe bronchus causing right lower lobe collapse. Large subcarinal nodes present and a right pleural effusion. A 2.6cm spiculated mass in the left breast. Bronchoscopy: demonstrated the classic “oat cells” of small cell lung cancer with pyknotic nuclei and sparse cytoplasm. Fig.3 Macroscopic image Fig.4 Nuclear moulding, salt and Tumour right main bronchus pepper chromatin, scant cytoplasm Breast Metastases from Small Cell Lung Cancer: A Case Report. L. Dunphy, J. Hanks, S. Deshpande. The University of Birmingham Medical School. Introduction: Metastatic tumours to the mammary glands are relatively uncommon, constituting about 2% of all breast malignancies. Such lesions can pose diagnostic dilemmas for both the clinician and the pathologist. Pleural Fluid Cytology. Pap Stain: small dark cells with prominent nuclear moulding, finely granular chromatin, inconspicuous nucleoli, scanty cytoplasm and indistinct cell margins Fig. 6 Pleural fluid cytology. Core Biopsy Left Breast: Macroscopic details: 6 cores of fibro fatty tissue ( 2– 18mm). Widely infiltrated by poorly differentiated tumour compound of small duct cells with hyperchromatic nuclei. Immunostaining:  Negative for CK5/6, BRST2 and S100  Appearances are those of small cell carcinoma  Metastasis from the lung Fig. 7 Positive for TTF1, CD56, Synaptophysin Fig.8 Cytokeratin (AE1/AE3) immunostain. Dot-like staining along the nuclear membrane is a characteristic feature of this immunostain in small cell lung carcinoma. A negative oestrogen and progesterone receptor status was noted. A diagnosis of small cell carcinoma from the lung was rendered. Unfortunately, due to her extensive disease and co morbidities she was palliated with cisplatin. Discussion: Sitzentfrey, in 1907, was the first to publish a case of ovarian carcinoma metastases to the breast. Since then a wide variety of malignancies have been reported to metastasize to the breast and according to the literature the most common primary tumours are melanomas and haematological malignancies. Despite the fact that the lung is the most common cancer site in terms of incidence and mortality there are only a few published cases on pulmonary carcinomas metastasizing to the breast. Small cell carcinomas, either from pulmonary or extra-pulmonary site, are aggressive in their behaviours and require combined modalities of treatment including chemotherapy. Metastatic mammary carcinoma is usually well- defined with absence of characters of primary breast carcinoma. Fig. 9 Normal breast microscopy Fig. 10 Small cell carcinoma of the breast Conclusion: This case is an attempt at high lighting the difficulties in differentiating a pulmonary small cell neuro-endocrine carcinoma from an extra pulmonary carcinoma and in identifying the site of origin. A detailed clinical history, thorough clinical examination and appropriate investigations are essential. In addition to routine diagnostic techniques, immuno-histo- chemistry and in future, gene analysis can be of value in the differentiation and confirmation of the diagnosis. Levothyroxine Sodium50 mcg tds Procyclidine5 mg od HaematologyABGSsMSU Hb 16.3 CRP 181pH 7.406Leucocytes WBC 17.4 Glucose 7.4pC02 5.93Nitrite, Protein Albumin 35 Na 136pO2 2.39Blood +++ Ultrasound left Breast: An irregular, hypoechoic mass in the UOQ of the breast, about 2mm diameter. Axilla – NAD. Fig. 5 Mammogram left breast. An irregular mass, 3cm in diameter present in the upper outer aspect of the left breast Duct Lobule “Streaming” of the tumour cells