Not only was the lesion in her breast more than 2cm in diameter, the cancer had also spread to the axillary lymph nodes in the armpit region. The doctors decided to put Chay on six courses of chemotherapy to shrink the tumour, and to control the spread of the cancer through the lymphatic system. If the chemotherapy was successful, she could have surgery to remove the cancer.

After three months of chemotherapy, Chay had another PET-CT scan. The good news was the lesions in the breast and axillary lymph nodes had shrunk. The bad news - the scan detected that one of the lymph nodes near her trachea (wind pipe) was enlarged. Her doctors believed the chemotherapy was only partially successful; surgery would not help Chay if the cancer was spreading despite the drugs.

She had another chemotherapy course before repeating the scan. The lymph node had enlarged even further. Her doctors tried another chemotherapy drug without success.

Chay sought a second opinion with specialists at Hong Kong Sanatorium and Hospital. There, the oncologist wanted to see if the enlarged lymph node was indeed related to the cancer. Because the node was within the thoracic cavity, it was hard to reach and required specialised skills and equipment. Dr Lam Bing, director of the Respiratory Medicine Centre, stepped in.

In the past, a technique called transbronchial needle aspiration (TBNA) would have been used. In this procedure, doctors use a CT image as a static 'map' to guide them. A small tube is inserted into the patient's airway and down the relevant bronchial branch, close to the lymph node in question. However, because the lymph node is located outside the airway, doctors can only guess its exact location. So, a needle is used to pierce the airway and, hopefully, the lymph node several times to extract the tissue. Poking about blindly carries risks - a blood vessel might be punctured. As a result, TBNA is used by fewer than 10 per cent of pulmonologists worldwide and has only a 50 per cent to 60 per cent success rate of locating the correct lymph node.

By the time Chay needed the biopsy, technology had provided new solutions that significantly reduced these risks.

Lam used an endobronchial ultrasound-guided TBNA (EBUS-TBNA), which carries a 95 per cent success rate of hitting the target. In this procedure, the bronchoscope has a small ultrasound probe at its tip, which allowed Lam to 'see' the enlarged lymph node in real time and accurately insert the needle into the lymph node to extract the tissue.

The biopsy showed that the enlarged lymph node was not caused by the cancer; instead, Chay had tuberculosis. Chemotherapy had impaired her immune system, which had previously held the tuberculosis bacteria from multiplying.

Lam says tuberculosis is common in Southeast Asia, and there are 6,000 cases each year in Hong Kong alone. However, the rate of infection is actually much higher, as nine out of 10 cases of TB go undetected. Most people's immune systems can suppress the bacteria, preventing a full-blown infection.

Chay underwent curative surgery to remove the cancerous lesions in her breast and axillary lymph nodes. She was also given hormonal therapy and later pronounced free of cancer.

Tackling the TB was easier. Chay was given a six-month course of medication. She had to take four types of medication for two months, followed by two other types for four months.

Lam says that so long as a patient is diligent about taking the medications regularly, TB is not difficult to cure. However, failure to comply with the regimen can result in a dangerous drug-resistant form of TB. Chay, who has always been conscientious about her health, followed Lam's orders to the letter and is now enjoying her newfound health.

Lam says Chay's case is a pertinent reminder that new symptoms in a cancer patient may not necessarily be related to the disease and should be investigated with an open mind. Tissue biopsies are crucial for accurate diagnoses, avoiding unnecessary treatments.