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    • Abstract: formation of true bone within extraskeletal soft. tissues. Classically, many diseases sharing this. common feature were lumped into the category. myositis ossificans; however, the term has fallen into. disfavor because primary muscle ... Intraabdominal myositis ossificans: a report of 9 new ...

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中華放射醫誌 Chin J Radiol 2010; 35: 67-70 67
Intraabdominal Heterotopic Ossification
after appendectomy Mimicking Undescended
Testicular Tumor: a rare case report and
literature review
R u ey-S heng C h ang1,4 I-L I L I n1 P I -C he C hen 2 J Ian -D e W u 3
Department of Medical Imaging1, Department of Urology2, Department of Pathology3, Chia-Yi Christian Hospital
Chang Gung Institute of Technology4, Chia-Yi Campus
Intraabdominal heterotopic ossif ication is a Heterotopic ossification (HO) is the abnormal
rare sequela of abdominal surgery or trauma. for mation of tr ue bone within extraskeletal soft
Only a few previous reports have been described tissues. Classically, many diseases shar ing this
in the literature. Here, we report the case of a com mon feat ure were lumped into the categor y
20-year-old man who underwent appendectomy 3 myositis ossificans; however, the term has fallen into
years ago and experinced this condition. Initially, disfavor because primary muscle inflammation is not
he presented with right undescended testis with a necessary precursor for such ossification and the
a palpable mass in the r ight lower abdomen. ossification does not always occur in muscle tissue.
Plain radiography and computed tomographic The term HO has largely replaced myositis ossifi-
imaging showed peripheral calcified soft tissue cans in the literature [1].
mass. Explorative laparotomy for excision was Mature HO closely resembles normal bone both
performed and heterotopic ossification was diag- histologically and radiologically, and thus it differs
nosed by pathologic findings. The characteristic from dystrophic calcification in soft tissues, in which
imaging features of this rare entity are discussed there is no osteoblastic activity or lamellar bone.
and the literature are reviewed. Heterotopic ossification has been reported in the
context of several conditions—most notably total hip
arthroplasty and neurologic injuries [2, 3]. However,
intraabdominal HO is a rare sequela of abdominal
surgery or trauma and of unknown etiology. Here,
we present a patient who experienced intraabdominal
HO after appendectomy.
A 20 year-old-young man presented with right
undescended testis during a military health examina-
tion. No previous trauma was reported but he had
a history of an appendectomy 3 years ago. Physical
examination revealed one painless palpable mass in
the right lower quadrant (RLQ) of the abdomen and
nonpalpable right testis at right scrotum and inguinal
Reprint requests to: Dr. Ruey-Sheng Chang area. Laboratory findings were within normal limit.
Department of Medical Imaging, Chia-Yi Christian Plain radiography of the abdomen demonstrated
Hospital. a large rim-calcified lesion in the RLQ area (Fig. 1).
No. 539, Jhongsiao Road, Chiayi 600, Taiwan, Computed tomography of the abdomen identified a
R.O.C. large peripheral mineralized soft tissue mass with
central puntate calcifications (Fig. 2). On the basis of
68 Intraabdominal heterotopic ossification
Figure 2. Unenhanced computed tomography reveals
large rim-calcified mass (arrows) in the RLQ mesentery
with central mineralization (black arrowhead).
Figure 1. Twenty-year-old man with undescened testis
with palpable RLQ mass. Abdominal radiography shows
large oval peripheral radiopaque mass lesion (arrows) in
the right lower abdomen.
the clinical history and radiolographic findings, the
preoperative diagnosis of an undescended testicular
tumor in the RLQ was suggested. An exploratory
laparotomy for t u mor excision was per for med.
Macrosopic examination of the resected specimen
revealed a 7.5 × 6 × 4.5 cm 3 whitish f ir m mass. Figure 3. Microscopically, fibroadipose tissue with ossfi-
Microscopically the tumor was composed of fibroadi- cation, calcification and fat necrosis is seen.
pose tissue with ossification and calcification (Fig. 3).
and connective tissue.
Heterotopic ossificationis an uncommon condi- It is quite unusual to see this process in the
tion and is characterized by new bone formation in mesentery and fewer than 20 cases of heterotopic
a tissue that does not usually undergo ossification. mesenteric ossification (HMO) are described in the
Several mechanisms have been described, but the English literature [1, 4]. HMO was first reported in
exact etiology is not clear. HO is usually a benign a 55-year-old man by Hansen et al in 1983 [5]. The
condition and the main challenge is to differentiate patient exhibited symptoms of small bowel obstruc-
it from other conditions. When HO occurs intraab- tion 2 weeks after he had a coloproctectomy for
dominally, however, this condition may have life- ulcerative colitis. He was found to have widespread
threatening complications. Multiple cases of HO intraabdominal fibrous adhesions and nodules of
after abdominal surgery or trauma are reported. It is heterotopic bone in the mesentery. His course was
confined to the operative incision, adjacent muscle, complicated by abscess formation, fistula formation,
Intraabdominal heterotopic ossification 69
and protracted gastrointestinal dysfunction. undergone malignant degeneration.
In reviewing the literature, the vast majority In conclusion, intraabdominal HO is a ver y
of cases involved adult men whose most common rare entity. It can easily be misdiagnosed and may
presentation was bowel obst r uction [5-7]. Both lead to serious complications. Nevertheless, in the
trauma and abdominal surgery have been consis- differential diagnosis of intraabdominal densities
t e nt ly id e nt i f ie d a s a nt e c e d e nt s t o H MO [4]. after abdominal surgery or trauma, HO should be
Fortunately, our patient didn’t experienced signifi- considered. It should be distinguished from dystro-
cant symptoms of bowel obstruction. phic calcification and ossifying neoplasm. 
T he mechan ism for i nt ra-abdom i nal HO is
unproven, but its morphologic appearance is quite REFEREnCE
similar to myositits ossificans [8], and it is likely to
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ment must be suitable for osteogenesis. Only a very ossification of the intestinal mesentery. Report of a case
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mature bone rather than dystrophic calcification. 11. Tonino BA, van der Meulen HG, Kuijpers KC, Mallens
Dyst roph ic calcif icat ion t y pically causes fai nt WM, van Gils AP. Heterotropic mesenteric ossification:
radiodense areas that are punctate and irregular [11]. a case report (2004:10b). Eur Radiol 2005; 15: 195-197
Additionally, mineralized neoplasm such extraskel- 12. Zamolyi RQ, Souza P, Nascimento AG, Unni KK.
etal osteosarcoma or extraskeletal chondrosarcoma Intraabdominal myositis ossificans: a report of 9 new
cases. Int J Surg Pathol 2006; 14: 37-41
generally show irregular, immature growth patterns 13. Secil M, Mungan U, Yorukoglu K, Dicle O. Case 89:
rather than the mature trabecular bone seen in HO Retroperitoneal extraskeletal osteosarcoma. Radiology
[13]. 2005; 237: 880-883
The recognition of HO is important because of
its propensity to recur and cause bowel obstruction
[6]. Treatments that have been suggested to decrease
regrowth include anti-inf lammatory medications,
disphosphonates, and radiotherapy [7, 12] We were
unable to find any cases documented in the literature
in which intraabdominal heterotopic ossification has
70 Intraabdominal heterotopic ossification
張瑞昇1,4 林怡里1 陳丕哲2 吳建德3
嘉義基督教醫院 影像醫學科1 泌尿外科2 病理科3
長庚技術學院 嘉義分部4
腹腔內異位性骨化十分罕見 ,我們報告一位 20 歲男性在三年前做過闌尾切除 。兵役體檢
時 ,因為單惻隱睪症併有右下腹腫塊而被轉介 。X 光素片及電腦斷層顯示環狀鈣化或骨化之腫
瘤於右下腹 。術前診斷為腹內睪丸腫瘤 ,腹腔鏡探測腫瘤切除後的病理診斷為異位性骨化 。我
們在文中討論這種罕見疾病的影像特徵並回顧文獻報告 。

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