A Case Report and Brief Literature Review on Dedifferentiated Chondrosarcoma in Proximal Phalanx: A Rare Location

Abstract

Dedifferentiated chondrosarcoma (DDCS) is a rare entity, constituting only 1-2% of all primary bone tumors, and has a dismal prognosis. Nearly two-thirds of the primary tumors of DDCSs are found in the appendicular skeleton, mostly involving the femur, humerus, and pelvis. DDCS of the small bones of the hand and foot are exceedingly rare with only four cases documented in the literature so far. In this report, we present a case of a 91-year-old woman with a rapidly growing bone tumor initially thought to be a trigger finger, which, on histologic examination of the amputation, turned out to be DDCS. On a follow-up CT scan, multiple pulmonary metastases were identified. Next-generation sequencing identified isocitrate dehydrogenase 2 (IDH2) (p.R172S, c.516G>T), TERT (c.-146C>T), and TP53 (c.559+1G>A) mutations. Microsatellite instability was equivocal and tumor mutation burden was low. Due to the advanced age of the patient, she was given palliative treatment and was alive at the six-month follow-up.

Dedifferentiated Chondrosarcoma from Molecular Pathology to Current Treatment and Clinical Trials

“…The most popular locations are femur (over 35% of cases), pelvis (up to 29% of cases), humerus (16%), as well as scapula (6%), rib (6%), and tibia (5%). In particular, femur is the most common location identified, in some case series constituting up to 44.5% of patients, while the humerus is the third most common location, but also in other types of bones, most primarily pelvic bones (second most common location identified in 22.2% of patients) and scapulae [9,16,26]. More frequently, it is located in the proximal rather than distal part of the previously mentioned long bones [27].…”

“…More frequently, it is located in the proximal rather than distal part of the previously mentioned long bones [27]. There has been a record of cases in which DDCS was localised in the ribs and phalanges of the hand and foot, but those locations are extremely rare [26]. Most of the neoplastic change is found in the medullary cavity, but approximately one in five cases are situated externally on the surface of the bone [4,28].…”

“…In contrast, the latter is fleshy and white with visible effects of hemorrhage with an extraosseous localisation [27,43]. Histological examination also has limitations since it is easy to omit one or the other component during tissue sampling [26]. It is best to carefully plan the biopsy procedure so it should be done after an MRI [4,19].…”