Pathology of Metastatic Tumors to Bone: Effects of Decalcification as Experienced at a Single Cancer Center

Abstract

IntroductionBone metastases are a frequent complication of renal cancer [1]. Breast and prostate cancer are the most common carcinomas to develop bone metastases, with an incidence of 65-75% and 68%, respectively [2]. In addition, carcinomas of lung, kidney, and thyroid give rise to bone metastases in approximately 30-40% of cases [1]. In contrast, gastrointestinal tract carcinomas rarely produce bone metastases (<10%) [3]. The primary problems that arise from bone metastases are pain, pathological fractures, spinal cord compression, hypercalcemia, and bone marrow suppression [1]. Decalcification ProcessBone, a specialized connective tissue, is composed of a collagenous and non-collagenous matrix proteins strengthened by deposits of calcium salts that play an essential role in the hard, rigid architecture and function of bone [3,4]. In order to study bone pathology, bone tissue is routinely placed within a formalin fixative followed by a decalcification procedure to remove the calcium salts. If a bone specimen is placed into a decalcification solution without prior formalin fixation the tissue will be macerated destroying tissue morphology and nuclear staining [5]. Removal of the calcium salts makes the bone tissue pliable and flexible which is necessary in order to section the tissue for microscopic evaluation. The decalcification procedure can be a lengthy process that may take several days or even weeks depending on the size of the bone. In our pathology department, once the tissue is submitted for decalcification the specimen is recorded into a log book detailing the date and time the specimen is placed into and removed from the Decal solution. Our pathology department uses a Decal solution named Nitrical which contains deionized water and nitric acid. Specimens in Decal solution are checked daily for pliability and softness. The Decal solution is changed on a regular basis due to the fact that the calcium ions that have been removed may saturate the solution preventing further decalcification. Occasionally, extremely rigid tissue may be processed within a microwave histoprocessor in order to decrease the amount of time for decalcification. Experienced histotechnologists test the completeness of decalcification through bending the tissue. Larger, denser bone specimens may be evaluated with X-ray radiographs to determine if the specimen is appropriately decalcified [5]. When the decalcification process is complete, the tissue is thoroughly washed in running tap water for 15-30 minutes to rinse off residual acid and neutralize the tissue. Appropriately size cut sections (0.5 cm in thickness overall size and volume not as critical as thickness) of bone tissue adequately formalin-fixed and decalcified are at this point able to be processed, embedded, and sectioned for light microscopy. All solutions utilized in the decalcification process are changed daily [6]. ResultsFrom January 2011 to August 2011 approximately 3076 specimens were submitted for decalcification according to the log book of which 86 specimens w...