cancers Article Primary Aneurysmal Bone Cyst and Its Recent Treatment Options: A Comparative Review of 74 Cases Nils Deventer, Martin Schulze , Georg Gosheger, Marieke de Vaal and Niklas Deventer * Department of Orthopedics and Tumororthopedics, Albert-Schweitzer-Campus 1, University Hospital Münster, 48149 Muenster, Germany; [email protected] (N.D.); [email protected] (M.S.); [email protected] (G.G.); [email protected] (M.d.V.) * Correspondence: [email protected] Simple Summary: This single-center study is a retrospective review of 74 patients with primary aneurysmal bone cysts (ABCs). It aims to compare the three most common treatment options— intralesional curettage, the percutaneous instillation of polidocanol and en bloc resection. It is the first study comparing these three treatment options using MR scans for the evaluation of the treatment success of instillation therapy and demonstrates the superiority of MRI scans compared to conventional radiographs for cyst volume measurement. The study confirms the efficacy of polidocanol instillations for primary ABCs and justifies it as standard treatment option. However, in this study several instillations were found to be necessary to achieve complete healing or at least stable disease. In a relevant number of cases a conversion to a surgical treatment was necessary. Thus, in this study we relativize the so-far highly positive treatment results reported for instillations in the literature, and rate them skeptically. Abstract: (1) Background: An aneurysmal bone cyst (ABC) is a benign, locally aggressive tumor. Citation: Deventer, N.; Schulze, M.; Different treatment modalities are described in the literature i.e., en bloc resection, intralesional Gosheger, G.; de Vaal, M.; Deventer, curettage and percutaneous sclerotherapy. (2) Methods: This single-center study is a review of N. Primary Aneurysmal Bone Cyst 74 patients with primary ABCs who underwent a surgical treatment or polidocanol instillation. Cyst and Its Recent Treatment Options: A volume measurements using MRI and conventional radiographs are compared. (3) Results: The mean Comparative Review of 74 Cases. pre-interventional MRI-based cyst volume was 44.07 cm3 and the mean radiographic volume was Cancers 2021, 13, 2362. https:// 27.27 cm3. The recurrence rate after intralesional curettage with the need for further treatment was doi.org/10.3390/cancers13102362 38.2% (13/34). The instillation of polidocanol showed a significant reduction of the initial cyst volume Academic Editor: Shinji Miwa (p < 0.001) but a persistent disease occurred in 29/32 cases (90.6%). In 10 of these 29 cases (34.5%) further treatment was necessary. After en bloc resection (eight cases) a local recurrence occurred in Received: 12 April 2021 two cases (25%), in one case with the need for further treatment. (4) Conclusions: MRI scans are Accepted: 11 May 2021 superior to biplanar radiographs in the examination of ABCs. Sequential percutaneous instillations of Published: 14 May 2021 polidocanol are equally effective in the therapy of primary ABCs compared to intralesional curettage. However, several instillations have to be expected. In a considerable number of cases, a conversion Publisher’s Note: MDPI stays neutral to intralesional curettage or en bloc resection may be necessary. with regard to jurisdictional claims in published maps and institutional affil- Keywords: aneurysmal bone cyst; intralesional curettage; polidocanol injection; polidocanol instillation iations. 1. Introduction Copyright: © 2021 by the authors. Aneurysmal bone cysts (ABCs) are benign, locally destructive growing bone tumors, Licensee MDPI, Basel, Switzerland. which were first described by Jaffé and Lichtenstein in 1942 [1]. They are most often This article is an open access article diagnosed in childhood and early adulthood. The literature reports that ABCs comprise distributed under the terms and 1–6% of all primary benign bone tumors [2–5]. Most cases of ABCs (75–90%) are reported conditions of the Creative Commons for patients younger than 20 years, with a slightly higher incidence for females [2,5,6]. Most Attribution (CC BY) license (https:// common localizations are the pelvis, the metaphysis of long bones and the spine, but ABCs creativecommons.org/licenses/by/ can also affect any other localization [2,5,7,8]. 4.0/). Cancers 2021, 13, 2362. https://doi.org/10.3390/cancers13102362 https://www.mdpi.com/journal/cancers Cancers 2021, 13, x FOR PEER REVIEW 2 of 12 Cancers 2021, 13, 2362 2 of 12 common localizations are the pelvis, the metaphysis of long bones and the spine, but ABCs can also affect any other localization [2,5,7,8]. TheThe clinicalclinical symptomssymptoms ofof anan ABCABC consistconsist ofof painpain andand swellingswelling inin thethe affectedaffected regionregion andand pathologicalpathological fracturesfractures cancan bebe observedobserved occasionally.occasionally. InIn conventionalconventional radiographyradiography aa relativelyrelatively well-definedwell-defined osteolytic, osteolytic, expansile expansile lesion lesion with with possible possible blowout blowout of the of periosteumthe perios- andteum a soap-bubbleand a soap-bubble appearance appearance can be found can be [2, 5found,6,8]. MRI [2,5,6,8]. scanning MRI shows scanning cystic shows formations cystic withformations typical with fluid-fluid typical levels fluid-fluid due to bloodlevels sedimentationdue to blood sedimentation [9]. Because of [9]. the Because possible rapidof the growthpossible with rapid local growth destruction, with local the literaturedestruction, describes the literature cases of describes ABCs that cases mimic of malignantABCs that bonemimic tumors malignant [10,11 bone]. Histologically, tumors [10,11]. an ABC Histologically, appears as aan solitary, ABC appears multicystic as a lesion,solitary, which mul- growsticystic rapidly lesion, andwhich is locallygrows destructiverapidly and [ 4is] locally (Figure destructive1). [4] (Figure 1). FigureFigure 1.1. CysticCystic elementselements ofof anan ABC.ABC. SeptaeSeptae ofof variablevariable thicknessthickness dividedivide thethe ABCABC intointo numerousnumerous blood-filledblood-filled cavitiescavities ofof differentdifferent sizessizes [[4,5,7,12].4,5,7,12]. ABCsABCs havehave beenbeen regardedregarded asas aa primaryprimary neoplasmneoplasm sincesince Panout-Panout- sakopoulossakopoulos etet al.al. [[13,14]13,14] andand OliveiraOliveira etet al.al. [[14–16]14–16] demonstrateddemonstrated thatthat a recurrent chromo-chromo- somesome aberration,aberration, t(16;17)t(16;17) (q22;p13),(q22;p13), leadsleads toto aa fusionfusion genegene ofof thethe entireentire ubiquitin-specificubiquitin-specific proteaseprotease 66 (USP6(USP6 aliasalias Tre2)Tre2) codingcoding sequencesequence atat 17p1317p13 andand thethe promoterpromoter regionregion ofof thethe osteoblastosteoblast cadherincadherin 1111 genegene (CDH11)(CDH11) atat 16q2216q22 [[17].17]. OliveiraOliveira etet al.al. [[15]15] identifiedidentified variousvarious rearrangementsrearrangements involvinginvolving USP6USP6 inin 69%69% ofof primaryprimary ABCsABCs andand inin nonenone ofof thethe secondarysecondary ABCs,ABCs, using fluorescence fluorescence in in situ situ hybridization hybridization (FISH). (FISH). Using Using next next generation generation sequencing, sequenc- ing,Guseva Guseva et al. et [18] al. [and18] andSekoranja Sekoranja et al. et [19] al. [increased19] increased the number the number of different of different gene generear- rearrangementsrangements involving involving USP6 USP6 observed observed in primary in primary ABCs ABCs to 100%. to 100%. ABCsABCs thatthat areare associatedassociated withwith aa preexistingpreexisting osseousosseous lesionlesion areare defineddefined asas secondarysecondary ABCs.ABCs. TheyThey representrepresent approximatelyapproximately 30%30% ofof allall ABCsABCs [[2,3,5].2,3,5]. SecondarySecondary ABCsABCs cancan occur,occur, e.g.,e.g., in cases cases of of a agiant giant cell cell tumor, tumor, chondroblastoma chondroblastoma or telangiectatic or telangiectatic osteosarcoma osteosarcoma [5]. The [5]. Theabsence absence of rearrangements of rearrangements involving involving USP6 USP6in secondary in secondary ABCs was ABCs confirmed was confirmed by Li et byal. Li[20]. et al.Thus, [20]. a Thus, biopsy a biopsywith histopathological with histopathological examinations examinations including including cytogenetic cytogenetic tech- techniques,niques, such such as FISH, as FISH, is necessary is necessary in order in order to diagnose to diagnose and to and distinguish to distinguish primary primary ABCs ABCsfrom secondary from secondary ABCs ABCs[10]. [10]. DifferentDifferent modalities modalities of of treatment treatment are are described described in in the the literature, literature, e.g., e.g., intralesional intralesional curet- cu- tagerettage with with adjuvants, adjuvants, en bloc en bloc resection, resection, embolization, embolization, percutaneous percutaneous injections injections of polidocanol of polido- or doxycycline, injection of bone marrow, cryoablation, radiation therapy, radionuclide canol or doxycycline, injection of bone marrow, cryoablation, radiation therapy, radionu- ablation, and the systemic use of bisphosphonates or denosumab [3,5,21,22]. The question clide ablation, and the systemic use of bisphosphonates or denosumab [3,5,21,22]. The of the optimal treatment option has not yet been clarified. The best local control rate can question of the optimal treatment