Inclusion Criteria:

- Metaplastic Infiltrating adenocarcinoma of the breast

- HER2 Overexpression by IHC and / or amplification (FISH and or ICHS)

- Positive diagnosis of neoplastic meningitis: positive CSF cytology (obtained within
28 days before inclusion) AND / OR clinical symptoms of neoplastic meningitis and
aspect of tumoral meningitis on MRI

- Brain metastases are allowed without prior treatment, if they are asymptomatics and
without engagement. In cases of symptomatic brain metastases, subjects could be
included only if surgery and / or radiotherapy (stereotactic or in toto) were
performed and if the cerebral metastatic localization allow IT or intra-ventricular
treatment. The last radiotherapy session or the surgery must have been done 3 weeks
before.

- Aged 18 years old or more

- Male and female

- Life expectancy more than 2 months

- Satisfactory Cardiac function: left ventricular ejection fraction (LVEF) determined
by ultrasound scan or myocardial scintigraphy

- Adequate Biological functions 14 days before inclusion, according to the criteria
below: Neutrophils > 1.0 x 109/L, Hemoglobin > 9.0 g/dL (+ transfusion if
needed,Platelets > 50 x 109/L,Bilirubin < 3 x N, ALT & AST < 10 x N, Creatinine < 2.0
mg/dL, Clearance > 25 mL/min (Cockcroft and Gault formula), Prothrombin time > 70 %,
Kaolin cephalin coagulation time < 1.5 x N.

- Women of childbearing potential, must take adequate birth control measure during the
study period and must have a negative pregnancy test (BetaHCG serum)

- The subjects must perform all evaluations of pre-inclusion, as provided by the
protocol

- Signed written inform consent

Exclusion Criteria:

- CSF circulation disorders suspected on MRI brain (obstructive hydrocephalus) or
medullar (obstacle) with, in case of a focal radiotherapy on obstructive lesion,
checking the restoration of transit traffic by isotope CSF

- Anti-coagulant effective dose treatment when trastuzumab administration by lumbar
puncture

- Patient on Lapatinib (wash out> 2 weeks from the date of first dose intrathecal
trastuzumab)

- Known or suspected trastuzumab allergy

- Contraindications of trastuzumab administration, including cardiac diseases: LVEF
subject to an unreasonable risk if he were to participate in the study

- Severe toxicity unresolved or unstable related to another previous study restricted
drug and / or a cancer treatment

- Ventriculoperitoneal or atrial shunting excepted if the valve could be turn off
(on-off switch) and the patient can stand it during 6 h after each injection of
trastuzumab

- Dementia, altered mental status or psychiatric condition that would prevent the
subject to understand or give informed consent

- Pre-existing severe cerebrovascular disease, such as stroke in a major vessel,
vasculitis in the central nervous system or malignant hypertension

- Uncontrolled infection

- Participation in a clinical study with an experimental molecule

- No affiliation to a Social insurance (beneficiary or assignee)

- Pregnant women, breastfeeding or of childbearing age not taking contraceptive

- Subject unable to make follow up schedule

- Persons deprived of liberty or under guardianship (including curators)