Inclusion Criteria:

Disease Characteristics:

All patients

• Histologic confirmation of the underlying malignancy
• Progressive, recurrent unresectable disease
• Absence of brain metastases or history of primary central nervous system tumor. Negative CT or MRI scan required if there are symptoms attributable to brain metastases
• No history of another primary cancer that is currently clinically significant, has potential for metastases, or currently requires active intervention
• Availability of a representative tumor tissue specimen

Phase II expansion part (advanced breast cancer)

• Confirmed positive hormone receptor (estrogen receptor and/or progesterone receptor) or positive HER2 expression status
• Disease progression/recurrence following hormonal or anti-HER-2 treatment for advanced disease
• At least one but not more than two prior chemotherapy regimens for the unresectable tumor
• Measurable disease by MRI or CT scan

Cowden Syndrome patients with an advanced malignancy

• Genetic confirmation of Cowden Syndrome

Patient Characteristics:

• Age ≥ 18
• World Health Organization (WHO) Performance Status of ≤ 2
• Life expectancy of ≥ 12 weeks
• Hematopoietic:
• Absolute neutrophil count at least 1,500/mm3
• Hemoglobin at least 9 g/dL
• Platelet count at least 100,000/mm3
• No diabetes mellitus or history of gestational diabetes mellitus
• Normal blood glucose tests
• No acute or chronic renal disease
• Creatinine ≤ 1.5 times the upper limit of normal or 24-hour clearance ≥ 50 mL/min
• No acute or chronic liver disease
• AST/SGOT and ALT/SGPT ≤ 2.5 times the upper limit of normal (ULN); ≤ 5 times ULN if liver metastases present
• Bilirubin ≤ 1.5 times ULN
• No acute or chronic pancreatitis
• Amylase and lipase within the upper limit of normal
• No peripheral neuropathy
• No unresolved diarrhea
• No impaired cardiac function or clinically significant cardiac diseases such as ventricular arrhythmia, congestive heart failure, uncontrolled hypertension
• No acute myocardial infarction or unstable angina pectoris within the past 3 months
• No progressive eye disease
• No impairment of gastrointestinal (GI) function or GI disease that may alter the absorption of BEZ235
• No other concurrent severe and/or uncontrolled medical conditions which could compromise participation in the study
• Known HIV infection (HIV testing not mandatory)
• Not pregnant or nursing
• Fertile patients must use barrier contraceptives

Prior/Concurrent Therapy:

• Recovered from side effects of prior anticancer therapies
• No concurrent treatment with medication that could prolong the QT interval
• No concurrent treatment with calcium channel blockers
• No concurrent treatment with therapeutic doses of warfarin sodium
• At least 4 weeks since prior chemotherapy or other systemic anticancer therapy
• At least 6 weeks since prior antibody therapy
• At least 2 weeks since prior treatment with corticosteroids, or with colony stimulating growth factors such as G-CSF or GM-CSF
• At least 4 weeks since prior radiotherapy
• At least 2 weeks since prior major surgery No concurrent investigational drugs

Exclusion Criteria:

Patients who have signs/symptoms attributable to brain metastases and have not been assessed with radiologic imaging to rule out the presence of brain metastases Prior treatment with a PI3K inhibitor Acute or chronic liver disease or renal disease Acute or chronic pancreatitis Patients with any peripheral neuropathy ≥ CTCAE grade 2 Patients with unresolved diarrhea ≥ CTCAE grade 2

Any of the following concurrent severe and/or uncontrolled medical conditions which could compromise participation in the study:

• Impaired cardiac function or clinically significant cardiac diseases
• Patients with diabetes mellitus requiring insulin treatment, history of gestational diabetes mellitus
• Patients with known coagulopathies (as per amendment 4)
• Other concurrent severe and/or uncontrolled concomitant medical conditions (e.g. active or uncontrolled infection) that could cause unacceptable safety risks or compromise compliance with the protocol Patients with a history of photosensitivity reactions to other drugs

Any of the following ophthalmological findings:

• Progressive eye disease that could lead to severe loss of visual acuity or visual field loss during the study period
• Inability to perform the ophthalmic procedures required in this protocol

Other protocol-defined inclusion/exclusion criteria may apply