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Primary muscular hydatidosis mimicking soft tissue tumour: a report of five cases


Hydatidosis is a zoonotic Zoonotic
A disease which can be spread from animals to humans.

Mentioned in: Zoonosis
 infection caused by larvae of Echinococcus granulosus, which is endemic in sheep-raising regions such as the Mediterranean and the Gulf states.1-3 Larvae penetrate the intestinal mucosa and enter the portal blood stream; 75% of remainder to the rest of the body (musculoskeletal involvement accounts for only 1 to 4%1-4 of cases). 20% of those infected develop multiple cysts.5 Primary involvement of skeletal muscle is rare and usually involves the pectoralis major, sartorius, biceps brachii, gracilis, supraspinatus, and biceps femoris.6-11

Hydatidosis usually presents as a slowly growing soft tissue mass, mimicking a tumour. Inappropriate biopsy may lead to cyst rupture and a risk of anaphylaxis and recurrence.7,12,13 Detailed radiological studies should be performed to achieve a correct diagnosis. Muscular hydatidosis should be considered in the differential diagnosis of soft tissue lesions in endemic areas.


Case 1

In May 1990, a 33-year-old man presented with a 3-year history of a slowly growing, soft, non-tender mass on the anterior aspect of his right leg. Laboratory tests and radiography were unremarkable. Ultrasonography revealed a cystic structure of 6x6x5 cm in the tibialis tibialis /tib·i·a·lis/ (tib?e-a´lis) [L.] tibial.


[L.] tibial.
 anterior. During surgery the cyst was ruptured, despite careful technique, and the wound was washed out with hypertonic hypertonic /hy·per·ton·ic/ (-ton´ik)
1. denoting increased tone or tension.

2. denoting a solution having greater osmotic pressure than the solution with which it is compared.
 saline. Microscopy revealed a fibrous laminar and inner germinal Germinal

conflict of capital vs. labor: miners strike en masse. [Fr. Lit.: Germinal]

See : Riot


portrays the sufferings of workers in the French mines. [Fr. Lit.
 layer consistent with hydatid disease. The patient had a recurrence at the same location 8 months later. The intradermal intradermal /in·tra·der·mal/ (-der´mal)
1. within the dermis.

2. intracutaneous.

Within or between the layers of the skin.
 Casoni test and serologic test (complement fixation test Noun 1. complement fixation test - a blood test in which a sample of serum is exposed to a particular antigen and complement in order to determine whether or not antibodies to that particular antigen are present; used as a diagnostic test  of Weinberg) were positive and an abdominal ultrasound was normal. A 3x3x2 cm mass was excised en bloc with surrounding healthy muscle. He was given 4 albendazole courses (10 mg/kg in one intake for 30 days) with 15-day intermissions between each course. At the 54-month follow-up there was no evidence of local or distant recurrence.

Case 2

In September 2000, a 37-year-old man presented with a one-year history of a painless mass in his left gluteus maximus. His range of movement was not affected. Computed tomography (CT) and magnetic resonance imaging magnetic resonance imaging (MRI), noninvasive diagnostic technique that uses nuclear magnetic resonance to produce cross-sectional images of organs and other internal body structures.  (MRI 1. (application) MRI - Magnetic Resonance Imaging.
2. MRI - Measurement Requirements and Interface.
) revealed a hypodense, cystic, nodular nodular

marked with, or resembling, nodules.

nodular dermatofibrosis
see dermatofibrosis.

nodular episcleritis
see nodular fasciitis (below).

nodular fasciitis
a firm painless nodular swelling, 0.
 mass measuring 4x6x7 cm. T1-weighted images revealed a low signal intensity mass with a low intensity rim (Fig. 1a). Post-gadolinium T1-weighted images showed considerable enhancement in the capsule and septa septa /sep·ta/ (sep´tah) [L.] plural of septum.
Septum (plural, septa)
The dividing partition in the nose that separates the two nostrils. It is composed of bone and cartilage.
 but no enhancement in the centre (Fig. 1b). Laboratory tests and CT of the thorax and abdomen were all normal. A large multilobulated mass with a fibrous capsule was excised. Histopathology his·to·pa·thol·o·gy
The science concerned with the cytologic and histologic structure of abnormal or diseased tissue.

The study of diseased tissues at a minute (microscopic) level.
 showed the cyst wall had a basophilic basophilic /ba·so·phil·ic/ (-fil´ik)
1. pertaining to basophils.

2. staining readily with basic dyes.


staining readily with basic dyes.
 lamella lamella /la·mel·la/ (lah-mel´ah) pl. lamel´lae   [L.]
1. a thin leaf or plate, as of bone.

2. a medicated disk or wafer to be inserted under the eyelid.
, scoleces, areas of fibrosis, necrosis, and a reactive pericystic structure with histiocytic histiocytic

pertaining to histiocytes.

histiocytic leukemia
see malignant histiocytosis.

histiocytic lymphocyte
 cells and degeneration of the adjacent muscle fibres. He was given 4 courses of albendazole (10 mg/kg in one intake for 30 days) with 15-day intermissions between each course. He had no evidence of recurrence at the 41-month follow-up.

Case 3

In May 2004, a 63-year-old woman presented with an 8-year history of a tender, firm, erythematous mass on the inner aspect of her left upper thigh, which had become painful 5 months earlier. She had undergone excision of a lesion in the same location 28 years previously but records of any pathological examination of the lesion were unavailable. Both T1- and T2-weighted MRI images revealed a multilocular multilocular /mul·ti·loc·u·lar/ (-lok´u-ler) having many cells or compartments.

Having or consisting of many small compartments or cavities.
 lesion measuring 20x12x15 cm with a low signal intensity rim. Both the Casoni and Weinberg tests were positive; all other laboratory investigations were normal. Both thoracic and abdominal CT were unremarkable. At operation a yellowish mass was dissected from the femoral vein and excised en bloc with the gracilis, with a wide margin from vastus medialis. One of the main branches of the femoral nerve supplying the vastus medialis was also excised. The femoral vein was damaged during dissection and repaired. The cavity was irrigated with hypertonic saline solution. Microscopically, the specimen showed areas of mixed inflammatory cells, multinucleated multinucleated

characterized by having more than one nucleus per cell.

multinucleated giant cell
see giant cell.
 giant cells, and epithelioid histiocytes. Cuticular membrane with a lamellar lamellar /la·mel·lar/ (lah-mel´ar)
1. pertaining to or resembling lamellae.

2. lamellated (1).


pertaining to or emanating from lamella.
 appearance was identified. The patient was given 4 courses of albendazole over 4 months. At the 24-month follow-up she had no major functional deficit or evidence of recurrence.

Case 4

In October 2002, a 75-year-old woman presented with a 5-month history of severe pain and swelling in the posterior aspect of her right thigh. She had undergone excision of a lesion 30 years previously but reports of any pathological examination of the lesion were unavailable. Ultrasonography and MRI showed a multivesicular cyst measuring 20x6.5x5 cm confined to the biceps femoris. It was hyperintense on T2-weighted images and had an incomplete rim with a low signal on both T1- and T2-weighted images. T1-weighted images showed internal cysts within the mother cyst, with low signal intensities (Fig. 2). Cranial, thoracic, abdominal, and pelvic CT did not provide any evidence of organ involvement. The lesion was excised en bloc along with a portion of the biceps femoris, semitendinosus, and semimembranosus muscles. A collection of pus was also debrided. The cavity was irrigated with hypertonic saline solution. No micro-organisms could be cultured, but the symptoms resolved with empirical antibiotic therapy. Histopathological examination of the removed tissue showed a cyst with cuticular membrane and scoleces, which are typical of hydatid disease. She was given 4 courses of albendazole courses and showed no signs of recurrence during 32 months of follow-up.

Case 5

In April 2003, a 34-year-old woman presented with a 5-month history of Echinococcus granulosus infestation infestation /in·fes·ta·tion/ (-fes-ta´shun) parasitic attack or subsistence on the skin and/or its appendages, as by insects, mites, or ticks; sometimes used to denote parasitic invasion of the organs and tissues, as by helminths.  in the posteromedial aspect of the right cruris after a tru-cut biopsy performed in another institution. MRI revealed a cystic mass measuring 4x3x2 cm confined to the gastrocnemius gastrocnemius /gas·troc·ne·mi·us/ (gas?tro-ne´me-?s) (gas?trok-ne´me-us) see under muscle.

n. pl.
, which was hyperintense on T2-weighted images with an incomplete, hypointense rim (Fig. 3a). Post-contrast images revealed enhancement at the periphery in T1-weighted images (Fig. 3b). Cranial, thoracic, and abdominal CT did not show any organ involvement. The lesion was excised along with a portion of the gastrocnemius. Pathological examination found a cystic structure with a cuticular membrane, scoleces, and infiltration of eosinophils Eosinophils
A leukocyte with coarse, round granules present.

Mentioned in: Histiocytosis X

. She received 3 courses of albendazole and was followed up for 38 months without recurrence.


Hydatidosis usually involves the liver and lungs because of their blood-filtering functions but can also affect other organs and the musculoskeletal system.1 Multiple cysts may occur in up to 20% of those infected; cysts may lodge in the musculoskeletal system via vascular seeding into highly vascularised areas such as the vertebrae, long bone epiphyses, ilia, skull, and ribs.4,14-16 Primary muscular hydatid cysts are rare (accounting for 3% of all patients with hydatidosis8) because of the contractility and high lactic acid levels in muscle.7,12,17,18 Involvement of the musculature of the chest wall, pectoralis major, sartorius, biceps brachii, supraspinatus, and biceps femoris have been reported.7-10 13 cases of muscular hydatidosis have been reported in the paravertebral pelvic gluteus glu·te·us
n. pl. glu·te·i
Any of the three large muscles of each buttock, especially the gluteus maximus, that extend, abduct, and rotate the thigh.
 and lower extremities.2 Tibialis anterior involvement has not been reported before. Muscular hydatidosis usually occurs as isolated lesions without hepatic or pulmonary lesions.1,2 None of our 5 cases had involvement of the liver, lungs or any other internal organs based on CT, ultrasonography, and radiography of their thoracic and abdominal cavities (Table).

Hydatidosis mimics primary tumours of the musculoskeletal system and is often misdiagnosed, because of the lack of specific clinical symptoms and radiological signs.4 Only 2 of 13 such cases had positive serological tests.2 Seronegativity does not exclude the diagnosis, but seropositivity may be helpful in recurrent cases.

Soft tissue masses and calcification may be seen in the radiographs of 38% of patients.19,20 None of our patients had soft tissue calcification. Ultrasonographical appearances pathognomonic pathognomonic /pa·thog·no·mon·ic/ (path?ug-no-mon´ik) specifically distinctive or characteristic of a disease or pathologic condition; denoting a sign or symptom on which a diagnosis can be made.  for hydatid cysts include echogenic hydatid hydatid /hy·da·tid/ (hi´dah-tid)
1. hydatid cyst.

2. any cystlike structure.

hydatid of Morgagni 
 sand (the 'snowflake sign'), unilocular cysts with daughter cysts ('honeycomb sign'), and cysts with a floating detached laminated membrane ('waterlily sign').21 In our series, ultrasonography was performed in 2 cases and both revealed multivesicular cysts.

MRI is useful for the differential diagnosis of hydatid disease and other soft tissue malignancies. The lesion usually has a high signal intensity on T2- weighted images and low intensity on T1-weighted images with a low intensity rim on both T1- and T2- weighted images.6,17,22 This rim sign is not specific for hydatid disease and can be seen in other lesions with a fibrous capsule or a calcific calcific /cal·cif·ic/ (-ik) forming lime.


forming lime.
 rim.12,14 Peripheral enhancement reflects the vascularity of the pericyst.12 The cystic structure with internal cysts was observed in 3 of our patients. Daughter cysts are the most characteristic feature of hydatid disease and imply viability, but 30% of hydatid cysts may lack daughter cysts.12

Incisional biopsy and marginal excision are contraindicated in hydatid disease because the cysts contain foreign proteins and scoleces that may precipitate anaphylaxis.7,12,18 Chemotherapy alone (such as benzimidazole ben·zim·id·az·ole
A crystalline compound that is used in organic synthesis and that inhibits the growth of certain microorganisms and parasitic worms.


a group of compounds with anthelmintic properties.
) is not usually sufficient in muscular hydatidosis. The curative method is complete and wide excision, similar to oncologic procedures.3,13 Total removal of hydatid lesions may be difficult to achieve because of the neighbouring neurovascular structures, which make preoperative evaluation crucial. When a wide excision is infeasible, meticulous drainage and adjuvant hypertonic saline irrigation is preferred.10 Intra-operative irrigation with scolecidal agents such as hypertonic saline prevents recurrence from inoculation of scoleces during excision.7 Leakage of cyst contents and dissemination of viable scoleces increase the recurrence rates.7,12 In our series, the excision was wide in 3 and marginal in 2 cases. Marginal excision was performed because of the proximity of the lesion to vascular structures, and hypertonic saline irrigation was used as an adjuvant treatment. Recurrence occurred in one patient 8 months later and he recovered with further wide excision and albendazole therapy.

Pharmacological complementary treatments (3 or 4 courses lasting 4 weeks separated by 14-day intervals as used in bone involvement23-25) are recommended. All our patients received 3 or 4 courses of albendazole (10 mg/kg in one intake for 30 days) with 2 weeks between each course.


Primary muscular hydatidosis may present as a slowly growing soft tissue mass and mimic a soft tissue tumour. Interventional diagnostic procedures should be avoided to prevent anaphylaxis from spontaneous or iatrogenic iatrogenic /iat·ro·gen·ic/ (i-a´tro-jen´ik) resulting from the activity of physicians; said of any adverse condition in a patient resulting from treatment by a physician or surgeon.  rupture of the hydatid cyst. Adequate preoperative planning and wide excision are recommended, as inadequate surgery or biopsy may lead to recurrence. Primary muscular hydatidosis should be considered in the differential diagnosis of soft tissue lesions, especially regions where the parasite is endemic.

© 2008 Western Pacific Orthopaedic Association Provided by ProQuest LLC. All Rights Reserved.
Copyright 2008 Journal of Orthopaedic Surgery
No portion of this article can be reproduced without the express written permission from the copyright holder.
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Author:K Basarir and Y Saglik and Y Yildiz and T Yetis and O Cebesoy
Publication:Journal of Orthopaedic Surgery
Date:Dec 1, 2008
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