- Email: [email protected]
Soft-tissue osteochondroma of the heel pad: A case report and review of literature
Foot and Ankle Surgery 16 (2010) e76–e78
Contents lists available at ScienceDirect
Foot and Ankle Surgery journal homepage: www.elsevier.com/locate/fas
Case report
Soft-tissue osteochondroma of the heel pad: A case report and review of literature Roop Singh a,*, Mantu Jain a, Ramchander Siwach a, Rajeev Sen b, Rajesh Kumar Rohilla a, Kiranpreet Kaur c a
Department of Orthopaedic Surgery, Paraplegia & Rehabilitation, Pt. B.D. Sharma PGIMS, Rohtak 124001, Haryana, India Department of Pathology, Pt. B.D. Sharma PGIMS, Rohtak 124001, Haryana, India c Department of Anaesthesiology and Critical care, Pt. B.D. Sharma PGIMS, Rohtak 124001, Haryana, India b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 27 December 2009 Accepted 4 May 2010
Extraskeletal osteochondroma of the foot are rare benign cartilaginous tumours. We present a case of soft-tissue osteochondroma in the heel pad superficial to the postero-inferior aspect of the calcaneus. We propose the pathogenesis of this lesion might be related to metaplasia in the plantar aponeurosis as described in literature, or it may be a fracture of the calcaneal osteochondroma, growing and presenting as soft-tissue lesion in the heel pad. ß 2010 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.
Keywords: Heel pad Osteochondroma Extraskeletal osteochondroma Metaplasia Calcaneus
1. Introduction Osteochondral neoplasms of soft tissue are uncommon and usually arise from synovial tissue of joints and tendon sheaths [1]. Rarely extra skeletal osteochondromas with extensive ossification arise outside synovial compartments in the soft tissue. Although the precise cause is unknown, some authors believe its origin to be metaplastic [2]. There are tumours in the foot only a few case reports about the occurrence of these tumours in foot [3–7]. We report a patient with soft-tissue osteochondroma in the heel pad and review the literature of these tumours in the foot. 2. Case report A 42-year-old male presented to our tertiary care centre with a small palpable mass in the left heel pad for last 2 years. Initially the swelling was an occasional discomfort, but for last 6 months after a trivial injury of missing a step of the stairs, it had increased in size and become painful during ambulation. Bare foot walking was not possible and patient was using soft insole in the shoes. There was no family history of tumours, metabolic or rheumatic conditions. Physical examination revealed a hard nontender mass approximately 3 cm 2 cm on the heel pad deep to the subcutaneous
* Corresponding author at: 9-J/52, Medical Enclave, PGIMS, Rohtak 124001, Haryana, India. Tel.: +91 1262 213171; fax: +91 1262 211301. E-mail address: [email protected] (R. Singh).
tissue and relatively immobile (Fig. 1). The overlying skin was slightly thickened but free from the underlying mass. The patient had full range of movements of adjoining joints. Plain radiographs showed a well delineated mass in the postero-inferior region of the calcaneus in the heel pad (Fig. 2). There was no scalloping or cortical destruction of the overlying calcaneus and there was a distinct gap between the calcaneus and the mass. Routine hematological investigations were within normal limits. Decision for excision biopsy was made as fine needle aspiration and cytology was unsuccessful. At surgery, a well formed pseudo capsule surrounded the mass. The mass did not violate the adjoining bone and joint surfaces and no muscles/tendons were adherent to the mass. The resected specimen was 3 cm 2.5 cm 2 cm with smooth margins and glistening surface (Fig. 3). Cut section showed well formed bone in the centre and the surfacee covered with cartilage. On histopathological examination the mass disclosed well formed partly lobulated mature hyaline cartilage surrounded by fibrous tissue at the periphery and extensive areas of ossification in the centre. There was no evidence of malignant features, and absence of mitotic activity. There was no chondroblastic or chondrogenic differentiation or zonal phenomenon. No synovial tissue was identified (Fig. 4). The final pathological diagnosis of extra skeletal osteochondroma was established. Post-operative recovery was uneventful. The patient returned to his activities of daily living two weeks after the procedure. When last reviewed 26 months after the excision, he was asymptomatic, with no clinical and radiographic signs of recurrence of the lesion.
1268-7731/$ – see front matter ß 2010 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.fas.2010.05.004
R. Singh et al. / Foot and Ankle Surgery 16 (2010) e76–e78
e77
Fig. 1. Clinical photograph showing swelling on the plantar aspect of the calcaneus. Overlying skin is slightly thickened (arrow).
3. Discussion Osteochondroma is a common benign neoplasm that develops mostly around the growth plate of long bones, especially the knee. The tumour demonstrates mature bone with a cartilaginous cap and continuity with the medullary cavity, and usually stops growing with closure of the growth plate. Infrequently such neoplasms arises in the soft tissues. 75% of these occur in the hand and 25% in feet [8,9]. Li et al. in 1989 [4] reported 3 cases of benign soft-tissue osteochondromas. Two cases were located in soft tissue beneath the calcaneus, the other was in the soft tissue near the left ankle joint. Gayle et al. [3] in 1999 reported case of osteochondroma in medial right forefoot. Nakanishi et al. [6] reported a case in the soft tissue superficial to plantar aspect of calcaneus. In 2005, Sheff and Wang [7] reported a single case of osteochondroma of the left foot and presented review of literature regarding this uncommon lesion. In 2008, Spencer and Blitz [5] presented a giant extraskeletal osteochondroma in the plantar medial longitudinal arch of the foot. Less frequent sites have been described including trunk, thigh, buttock, neck and larger joints [10–12]. The pathogenesis of such tumour remains controversial. Lynn and Lee [13] emphasized that cartilage formation in soft tissue may occur by three different methods: (1) cell capable of producing cartilage migrate from their origin near bone and become adherent to the connective tissue; (2) precartilagenous tissue persisting in the tendon just above the joint of its insertion converts to active phase; (3) metaplasia occurs when synovial cell differentiates into cartilage simulated by unknown factors. Metaplasia of pleuripotent cell line derived from the joint synovium, tenosynovium, and connective tissue is considered the most common theory regarding the origin of tumour cells [4]. About the origin of the tumour in the present case may be similar to those proposed by Li et al. [4] i.e. from relatively undifferenti-
Fig. 2. Lateral view radiograph of left foot shows a well defined bony mass in the subcutaneous tissue on the postero-inferior aspect of calcaneus. No bony changes are seen in the calcaneus and there is a clear gap between the mass and the calcaneus.
ated mesenchymal cells or metaplasia from the fibroblasts in the loose connective tissues. The other possibility could be the fact that the tumour, arose as an osteochondroma of the calcaneus, got fractured after injury and separated to form a soft tissue mass. This possibility gets substance as calcaneus is the most unusual site in the foot for an osteochondroma [14–16] and there is possibility of fracture of such lesion during walking/post-injury. However, we could not find any abnormality of calcaneus radiologically or peroperatively to substantiate this theory except for a history of trivial trauma. The tumour typically occurs in the adults although no age is bar. Antecedent trauma has reported in few cases again the stimuli in most cases remain unknown [17]. The behavior of extraskeletal osteochondroma is poorly characterized but limited data suggests that they have a benign fashion and local recurrence is rare [18]. The radiographic finding of extraskeletal osteochondroma typically consists of a well circumscribed, lobulated mass with dense central calcification or areas of ossification [4,19,20]. Bony changes are infrequent, but occasionally, cortical sclerosis, and even cortical erosions have been described. CT demonstrates the extraskeletal location and central dense calcification or ossification of osteochondroma [12,13]. MRI shows a well demarcated heterogenous lesion which has low signal mostly on T1 weighted images and mixed high and low in T2 weighted images. Areas of mature ossification have intermediate T2 signal intensity except for densely calcified areas which again have low signal intensity [8,9].
Fig. 3. (a) Excised mass covered all over by the glistening cartilage and cut section shows well defined cancellous bone in the centre (b).
e78
R. Singh et al. / Foot and Ankle Surgery 16 (2010) e76–e78
described in literature, or it may be a fracture of the calcaneal osteochondroma, growing and presenting as soft-tissue lesion in the heel pad. Conflict of interest None. References
Fig. 4. photomicrograph shows mature hyaline cartilage (*), fibrous capsule at the periphery (red arrow), ossification in the centre (green arrow), and fibro-adipose tissue of the calcaneal pad on the left of the image (line arrow).
Various possible differential diagnoses such as myositis ossificans, lipomatous lesion, tumoural calcinosis, extraskeletal chondroma, psuedomalignant osseous tumours, synovial chondromatosis, and synovial sarcoma should be kept for discrete soft tissue masses showing calcification and ossification [10]. Myositis ossificans demonstrates a ‘zonal phenomenon’ of peripheral calcification. It is often inhomogeneous or amorphous in its early stages and may increase or decrease in size in few weeks [3,19,21]. Extraskeletal chondroma and enchondral ossification shows chondrogenic or chondroblastic differentiation of the inner part of mass with distinct cartilage cap and fibrous capsule [4]. Synovial chondromatosis usually have multiple osteochondrous nodules of synovium with loose bodies in the joint [4,19,21]. Tumoral calcinosis is well defined calcified calcific mass with layering when imaged with horizontal beam [4,19,22]. Synovial sarcoma may show calcification but may have coexistent adjacent bony lesion, and is cytologically active and atypical [4,23]. Chondrosarcoma and osteosarcoma have scattered, patchy and amorphous calcification with distinct clinic-histological findings [4,9]. The recommended treatment of soft-tissue osteochondromas is wide excision [8,9]. The tumours are benign and do not metastasize. The local recurrence rate has been described as 17% to 18% [9]. Recurrent tumours are treated with repeated wide excision when possible and more radical excision when indicated [8,9]. 4. Conclusion A unique case of extra skeletal osteochondroma of the heel pad is presented here. We propose the pathogenesis of this lesion might be related to metaplasia in the plantar aponeurosis as
[1] Weiss SW, Goldblum JR. In: Weiss SM, Goldbrum JR, Enzinger FM, editors. Enzinger and Weiss Soft Tissue Tumors. 4th ed., St. Louis, MO: Mosby; 2001. p. 1361–85. [2] Han JY, Han HS, Kim YB, Kim JM, Chu YC. Extraskeletal chondroma of the fallopian tube. J Korean Med Sci 2002;17:276–8. [3] Gayle EL, Morrison WB, Carrino JA, Parsons TW, Liang CY, Stevenson A. Extraskeletal osteochondroma of the foot. Skeletal Radiol 1999 Oct;28(10): 594–8. [4] Li C, Arger PH, Dalinka MK. Soft tissue osteochonroma. A report of three cases. Skeletal Radiol 1989;18:435–7. [5] Spencer RJ, Blitz NM. Giant extraskelatal osteochondroma of the plantar midfoot arch. J Foot Ankle Surg 2008;47(4):362–7. [6] Nakanishi H, Araki N, Mukai K, Ohno H, Matsui Y, Hosaya T. Soft-tissue osteochondroma in the calcaneal pad: a case report. J Foot Ankle Surg 2001;40(6):396–400. [7] Sheff JS, Wang S. Extraskeletal osteochondroma of the foot. J Foot Ankle Surg 2005;44(1):57–9. [8] Chung EB, Enzinger FM. Chondroma of soft parts. Cancer 1978;41:1414–24. [9] Dahlin DC, Salvador AH. Cartilaginous tumors of tissues of hands and feet. Mayo Clinic Proc 1974;49:721–6. [10] Lim SC, Kim YS, Kim YS, Moon YR. Extraskeletal osteochondroma of buttock. J Korean Med Sci 2003;18:127–30. [11] Gulati Y, Maheswari A, Sharma V, Mattoo R, Arora D, Gupta N. Extraskeletal osteochondroma of thigh: a case report. Acta Orthop Belg 2005;71:115–8. [12] Singh R, Sharma AK, Magu NK, Kaur KP, Sen R, Magu S. Extraskeletal osteochondroma in nape of neck: a case report. Journal of Orthopedic Surg 2006;14:192–5. [13] Lynn MD, Lee J. Periarticular tenosynovaial chondrometaplesia. J Bone Joint Surg 1972;54:650. [14] Koplay M, Tober S, Sahin L, Kilincoglu V. A calcaneal osteochondroma with recurrence in skeletal mature patient: a case report. Cases J 2009;2:7013. doi: 10.4076/1757-1627-2-7013. [15] Blitz NM, Lopez KT. Giant solitary osteochondroma of the inferior medial calcaneal tubercle: a case report and review of literature. J Foot Ankle Surg 2008;47:206–12. [16] Nogier A, De Pinieux G, Hottaya G, Anract P. Case reports: enlargement of the calcaneal osteochondroma after skeletal maturity. Clin Orthop Relat Res 2006;449:260–6. [17] Cohen AP, Giannaoudis PV, Hinsche A, Smith RM, Matthews SJE. Post-traumatic giant intra-articular synovial osteochondroma of knee. Injury 2001;32:87–9. [18] Helpert C, Davies AM, Evans N, Grimer RJ. Differential diagnosis of tumors and tumor-like lesions of the infrapatellar (Hoffa’s) fat pad: pictorial review with an emphasis on MR imaging. Eur Radiol 2004;14:2337–46. [19] Sowa DT, Moore JR, Weiland AJ. Extraskeletal osteochondroma of the wrist. J Hand Surg 1987;12A:212–7. [20] Dienst M, Schneider G, Pahl S, Ensslin S, Kohn D. Intra-articular osteochondroma of the posterior cavity of the knee. Arch Orthop Trauma Surg 2002;122:462–5. [21] Karlin CA, De Smet AA, Neff JJ, Lin F, Horton W, Wertzberger JJ. The variable presentation of extra articular synovial chondromatosis. AJR 1981;137:731–5. [22] Palmer PE. Tumoral calcinosis. Br J Radial 1966;39:518–25. [23] Cadman NL, Soule EN, Kelly PJ. Synovial sarcoma: an analysis of 34 tumors. Cancer 1965;18:613–22.
Contents lists available at ScienceDirect
Foot and Ankle Surgery journal homepage: www.elsevier.com/locate/fas
Case report
Soft-tissue osteochondroma of the heel pad: A case report and review of literature Roop Singh a,*, Mantu Jain a, Ramchander Siwach a, Rajeev Sen b, Rajesh Kumar Rohilla a, Kiranpreet Kaur c a
Department of Orthopaedic Surgery, Paraplegia & Rehabilitation, Pt. B.D. Sharma PGIMS, Rohtak 124001, Haryana, India Department of Pathology, Pt. B.D. Sharma PGIMS, Rohtak 124001, Haryana, India c Department of Anaesthesiology and Critical care, Pt. B.D. Sharma PGIMS, Rohtak 124001, Haryana, India b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 27 December 2009 Accepted 4 May 2010
Extraskeletal osteochondroma of the foot are rare benign cartilaginous tumours. We present a case of soft-tissue osteochondroma in the heel pad superficial to the postero-inferior aspect of the calcaneus. We propose the pathogenesis of this lesion might be related to metaplasia in the plantar aponeurosis as described in literature, or it may be a fracture of the calcaneal osteochondroma, growing and presenting as soft-tissue lesion in the heel pad. ß 2010 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.
Keywords: Heel pad Osteochondroma Extraskeletal osteochondroma Metaplasia Calcaneus
1. Introduction Osteochondral neoplasms of soft tissue are uncommon and usually arise from synovial tissue of joints and tendon sheaths [1]. Rarely extra skeletal osteochondromas with extensive ossification arise outside synovial compartments in the soft tissue. Although the precise cause is unknown, some authors believe its origin to be metaplastic [2]. There are tumours in the foot only a few case reports about the occurrence of these tumours in foot [3–7]. We report a patient with soft-tissue osteochondroma in the heel pad and review the literature of these tumours in the foot. 2. Case report A 42-year-old male presented to our tertiary care centre with a small palpable mass in the left heel pad for last 2 years. Initially the swelling was an occasional discomfort, but for last 6 months after a trivial injury of missing a step of the stairs, it had increased in size and become painful during ambulation. Bare foot walking was not possible and patient was using soft insole in the shoes. There was no family history of tumours, metabolic or rheumatic conditions. Physical examination revealed a hard nontender mass approximately 3 cm 2 cm on the heel pad deep to the subcutaneous
* Corresponding author at: 9-J/52, Medical Enclave, PGIMS, Rohtak 124001, Haryana, India. Tel.: +91 1262 213171; fax: +91 1262 211301. E-mail address: [email protected] (R. Singh).
tissue and relatively immobile (Fig. 1). The overlying skin was slightly thickened but free from the underlying mass. The patient had full range of movements of adjoining joints. Plain radiographs showed a well delineated mass in the postero-inferior region of the calcaneus in the heel pad (Fig. 2). There was no scalloping or cortical destruction of the overlying calcaneus and there was a distinct gap between the calcaneus and the mass. Routine hematological investigations were within normal limits. Decision for excision biopsy was made as fine needle aspiration and cytology was unsuccessful. At surgery, a well formed pseudo capsule surrounded the mass. The mass did not violate the adjoining bone and joint surfaces and no muscles/tendons were adherent to the mass. The resected specimen was 3 cm 2.5 cm 2 cm with smooth margins and glistening surface (Fig. 3). Cut section showed well formed bone in the centre and the surfacee covered with cartilage. On histopathological examination the mass disclosed well formed partly lobulated mature hyaline cartilage surrounded by fibrous tissue at the periphery and extensive areas of ossification in the centre. There was no evidence of malignant features, and absence of mitotic activity. There was no chondroblastic or chondrogenic differentiation or zonal phenomenon. No synovial tissue was identified (Fig. 4). The final pathological diagnosis of extra skeletal osteochondroma was established. Post-operative recovery was uneventful. The patient returned to his activities of daily living two weeks after the procedure. When last reviewed 26 months after the excision, he was asymptomatic, with no clinical and radiographic signs of recurrence of the lesion.
1268-7731/$ – see front matter ß 2010 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.fas.2010.05.004
R. Singh et al. / Foot and Ankle Surgery 16 (2010) e76–e78
e77
Fig. 1. Clinical photograph showing swelling on the plantar aspect of the calcaneus. Overlying skin is slightly thickened (arrow).
3. Discussion Osteochondroma is a common benign neoplasm that develops mostly around the growth plate of long bones, especially the knee. The tumour demonstrates mature bone with a cartilaginous cap and continuity with the medullary cavity, and usually stops growing with closure of the growth plate. Infrequently such neoplasms arises in the soft tissues. 75% of these occur in the hand and 25% in feet [8,9]. Li et al. in 1989 [4] reported 3 cases of benign soft-tissue osteochondromas. Two cases were located in soft tissue beneath the calcaneus, the other was in the soft tissue near the left ankle joint. Gayle et al. [3] in 1999 reported case of osteochondroma in medial right forefoot. Nakanishi et al. [6] reported a case in the soft tissue superficial to plantar aspect of calcaneus. In 2005, Sheff and Wang [7] reported a single case of osteochondroma of the left foot and presented review of literature regarding this uncommon lesion. In 2008, Spencer and Blitz [5] presented a giant extraskeletal osteochondroma in the plantar medial longitudinal arch of the foot. Less frequent sites have been described including trunk, thigh, buttock, neck and larger joints [10–12]. The pathogenesis of such tumour remains controversial. Lynn and Lee [13] emphasized that cartilage formation in soft tissue may occur by three different methods: (1) cell capable of producing cartilage migrate from their origin near bone and become adherent to the connective tissue; (2) precartilagenous tissue persisting in the tendon just above the joint of its insertion converts to active phase; (3) metaplasia occurs when synovial cell differentiates into cartilage simulated by unknown factors. Metaplasia of pleuripotent cell line derived from the joint synovium, tenosynovium, and connective tissue is considered the most common theory regarding the origin of tumour cells [4]. About the origin of the tumour in the present case may be similar to those proposed by Li et al. [4] i.e. from relatively undifferenti-
Fig. 2. Lateral view radiograph of left foot shows a well defined bony mass in the subcutaneous tissue on the postero-inferior aspect of calcaneus. No bony changes are seen in the calcaneus and there is a clear gap between the mass and the calcaneus.
ated mesenchymal cells or metaplasia from the fibroblasts in the loose connective tissues. The other possibility could be the fact that the tumour, arose as an osteochondroma of the calcaneus, got fractured after injury and separated to form a soft tissue mass. This possibility gets substance as calcaneus is the most unusual site in the foot for an osteochondroma [14–16] and there is possibility of fracture of such lesion during walking/post-injury. However, we could not find any abnormality of calcaneus radiologically or peroperatively to substantiate this theory except for a history of trivial trauma. The tumour typically occurs in the adults although no age is bar. Antecedent trauma has reported in few cases again the stimuli in most cases remain unknown [17]. The behavior of extraskeletal osteochondroma is poorly characterized but limited data suggests that they have a benign fashion and local recurrence is rare [18]. The radiographic finding of extraskeletal osteochondroma typically consists of a well circumscribed, lobulated mass with dense central calcification or areas of ossification [4,19,20]. Bony changes are infrequent, but occasionally, cortical sclerosis, and even cortical erosions have been described. CT demonstrates the extraskeletal location and central dense calcification or ossification of osteochondroma [12,13]. MRI shows a well demarcated heterogenous lesion which has low signal mostly on T1 weighted images and mixed high and low in T2 weighted images. Areas of mature ossification have intermediate T2 signal intensity except for densely calcified areas which again have low signal intensity [8,9].
Fig. 3. (a) Excised mass covered all over by the glistening cartilage and cut section shows well defined cancellous bone in the centre (b).
e78
R. Singh et al. / Foot and Ankle Surgery 16 (2010) e76–e78
described in literature, or it may be a fracture of the calcaneal osteochondroma, growing and presenting as soft-tissue lesion in the heel pad. Conflict of interest None. References
Fig. 4. photomicrograph shows mature hyaline cartilage (*), fibrous capsule at the periphery (red arrow), ossification in the centre (green arrow), and fibro-adipose tissue of the calcaneal pad on the left of the image (line arrow).
Various possible differential diagnoses such as myositis ossificans, lipomatous lesion, tumoural calcinosis, extraskeletal chondroma, psuedomalignant osseous tumours, synovial chondromatosis, and synovial sarcoma should be kept for discrete soft tissue masses showing calcification and ossification [10]. Myositis ossificans demonstrates a ‘zonal phenomenon’ of peripheral calcification. It is often inhomogeneous or amorphous in its early stages and may increase or decrease in size in few weeks [3,19,21]. Extraskeletal chondroma and enchondral ossification shows chondrogenic or chondroblastic differentiation of the inner part of mass with distinct cartilage cap and fibrous capsule [4]. Synovial chondromatosis usually have multiple osteochondrous nodules of synovium with loose bodies in the joint [4,19,21]. Tumoral calcinosis is well defined calcified calcific mass with layering when imaged with horizontal beam [4,19,22]. Synovial sarcoma may show calcification but may have coexistent adjacent bony lesion, and is cytologically active and atypical [4,23]. Chondrosarcoma and osteosarcoma have scattered, patchy and amorphous calcification with distinct clinic-histological findings [4,9]. The recommended treatment of soft-tissue osteochondromas is wide excision [8,9]. The tumours are benign and do not metastasize. The local recurrence rate has been described as 17% to 18% [9]. Recurrent tumours are treated with repeated wide excision when possible and more radical excision when indicated [8,9]. 4. Conclusion A unique case of extra skeletal osteochondroma of the heel pad is presented here. We propose the pathogenesis of this lesion might be related to metaplasia in the plantar aponeurosis as
[1] Weiss SW, Goldblum JR. In: Weiss SM, Goldbrum JR, Enzinger FM, editors. Enzinger and Weiss Soft Tissue Tumors. 4th ed., St. Louis, MO: Mosby; 2001. p. 1361–85. [2] Han JY, Han HS, Kim YB, Kim JM, Chu YC. Extraskeletal chondroma of the fallopian tube. J Korean Med Sci 2002;17:276–8. [3] Gayle EL, Morrison WB, Carrino JA, Parsons TW, Liang CY, Stevenson A. Extraskeletal osteochondroma of the foot. Skeletal Radiol 1999 Oct;28(10): 594–8. [4] Li C, Arger PH, Dalinka MK. Soft tissue osteochonroma. A report of three cases. Skeletal Radiol 1989;18:435–7. [5] Spencer RJ, Blitz NM. Giant extraskelatal osteochondroma of the plantar midfoot arch. J Foot Ankle Surg 2008;47(4):362–7. [6] Nakanishi H, Araki N, Mukai K, Ohno H, Matsui Y, Hosaya T. Soft-tissue osteochondroma in the calcaneal pad: a case report. J Foot Ankle Surg 2001;40(6):396–400. [7] Sheff JS, Wang S. Extraskeletal osteochondroma of the foot. J Foot Ankle Surg 2005;44(1):57–9. [8] Chung EB, Enzinger FM. Chondroma of soft parts. Cancer 1978;41:1414–24. [9] Dahlin DC, Salvador AH. Cartilaginous tumors of tissues of hands and feet. Mayo Clinic Proc 1974;49:721–6. [10] Lim SC, Kim YS, Kim YS, Moon YR. Extraskeletal osteochondroma of buttock. J Korean Med Sci 2003;18:127–30. [11] Gulati Y, Maheswari A, Sharma V, Mattoo R, Arora D, Gupta N. Extraskeletal osteochondroma of thigh: a case report. Acta Orthop Belg 2005;71:115–8. [12] Singh R, Sharma AK, Magu NK, Kaur KP, Sen R, Magu S. Extraskeletal osteochondroma in nape of neck: a case report. Journal of Orthopedic Surg 2006;14:192–5. [13] Lynn MD, Lee J. Periarticular tenosynovaial chondrometaplesia. J Bone Joint Surg 1972;54:650. [14] Koplay M, Tober S, Sahin L, Kilincoglu V. A calcaneal osteochondroma with recurrence in skeletal mature patient: a case report. Cases J 2009;2:7013. doi: 10.4076/1757-1627-2-7013. [15] Blitz NM, Lopez KT. Giant solitary osteochondroma of the inferior medial calcaneal tubercle: a case report and review of literature. J Foot Ankle Surg 2008;47:206–12. [16] Nogier A, De Pinieux G, Hottaya G, Anract P. Case reports: enlargement of the calcaneal osteochondroma after skeletal maturity. Clin Orthop Relat Res 2006;449:260–6. [17] Cohen AP, Giannaoudis PV, Hinsche A, Smith RM, Matthews SJE. Post-traumatic giant intra-articular synovial osteochondroma of knee. Injury 2001;32:87–9. [18] Helpert C, Davies AM, Evans N, Grimer RJ. Differential diagnosis of tumors and tumor-like lesions of the infrapatellar (Hoffa’s) fat pad: pictorial review with an emphasis on MR imaging. Eur Radiol 2004;14:2337–46. [19] Sowa DT, Moore JR, Weiland AJ. Extraskeletal osteochondroma of the wrist. J Hand Surg 1987;12A:212–7. [20] Dienst M, Schneider G, Pahl S, Ensslin S, Kohn D. Intra-articular osteochondroma of the posterior cavity of the knee. Arch Orthop Trauma Surg 2002;122:462–5. [21] Karlin CA, De Smet AA, Neff JJ, Lin F, Horton W, Wertzberger JJ. The variable presentation of extra articular synovial chondromatosis. AJR 1981;137:731–5. [22] Palmer PE. Tumoral calcinosis. Br J Radial 1966;39:518–25. [23] Cadman NL, Soule EN, Kelly PJ. Synovial sarcoma: an analysis of 34 tumors. Cancer 1965;18:613–22.