乳癌蝕骨性骨轉移之診斷──個案報告

Diagnosis of Osteolytic Bone Metastases in Breast Cancer: A Case Report

骨骼是乳癌患者最容易發生遠處轉移的器官。臨床上評估是否有骨轉移最常用核醫骨骼掃描，是將「鎝-99m甲基雙磷酸鹽」（Tc-99m MDP）經由靜脈注射至人體。當癌細胞轉移至骨頭後，會破壞骨組織，進而刺激周圍的骨骼修復；修復的新生骨會吸收更高的鈣及磷酸鹽，並於骨骼掃描上呈現放射性增高的影像。然而當乳癌細胞入侵骨骼後，會刺激蝕骨細胞（Osteoclast）的生長，則可能在骨骼掃描影像上表現較不明顯。一名48歲女性，於2018年發現乳癌並接受乳房全切除手術併前哨淋巴結摘除手術及標準腋下淋巴廓清術。每隔三個月到一年定期做骨骼掃描追蹤皆無骨轉移發生。2020年6月發現CA-153升高，7月進行正子斷層造影（PET/CT）檢查，發現在左側鎖骨、胸骨、左側第6根肋骨、第7節胸椎、右邊肩胛骨、第4節腰椎、左右兩側骨盆、髂骨及左側股骨皆有骨轉移發生。骨骼掃描為平面影像容易因相對位置重疊且因蝕骨細胞的生長，骨頭吸收Tc-99m MDP較少在影像上表現不明顯而不易被發現。如鎖骨與肋骨、胸骨與胸椎、肩胛骨與肋骨等都易重疊。因此，正子斷層造影可以幫助乳癌蝕骨性骨轉移的診斷。

The bone is the most common site for distant metastasis in breast cancer patients. Clinically, a bone scintigraphy is most commonly utilized to assess the presence of bone metastases, by intravenous injection of technetium 99m-methyl diphosphonate (Tc-99m MDP) into the human body. When cancer cells metastasize to the bone, they destroy the bone tissue and stimulate bone repair of the affected area. The new bone absorbs higher amounts of calcium and phosphate and shows increased radioactivity on bone scintigraphy. However, when breast cancer cells invade the bone, they stimulate the proliferation of osteoclasts, which may be less obvious on bone scintigraphy images. In 2018, a 48-year-old woman was diagnosed with breast cancer and underwent total mastectomy, and axillary lymph node dissection. No bone metastases were found in the regular bone scintigraphy performed every three months to one year. In June 2020, the level of CA-153 was found to be elevated. A positron emission tomography/computed tomography (PET/CT) scan was performed in July. Bone metastases were discovered in the left clavicle, sternum, left sixth rib, seventh thoracic vertebra, right scapula, fourth lumbar, left and right pelvis, ilium, and left femur. The bone scintigraphy is a planar image that is prone to overlap due to the relative positions. Because of the proliferation of osteoclasts, the bones absorb less Tc-99m MDP, resulting in less obvious manifestations in the bone scintigraphy images that were not easily detected. For instance, the clavicle and the ribs, the sternum and the thoracic vertebrae, and the scapula and the ribs can easily overlap. The PET/CT scan can help diagnosis of osteolytic bone metastases in breast cancer.