Extra skeletal osteochondroma is a slow-growing tumor. The highest incidences reported are in the hands and feet. The foot is the second most common are after the fingers, where more than 80% of soft tissue chondroma are found . Sporadic cases have been reported in the skin, nape of the neck, oral cavity, buttocks, thighs, knees, pharynx and parotid gland [13,18-21]. The causes of extra skeletal osteochondroma are still unknown, but there is one.
Hypothesis that it originates from pluripotent cell lines derived from the joint synovium, tenosynovium, or connective tissue. Another theory states, that it originates from metaplasia tendon sheaths in the hands and feet [1,8,17-21]. There is one more theory, that extraskeletal osteochondroma arises from fibroblasts in the connective tissue distant from bone and joints because of unknown stimuli . Extra skeletal osteochondroma generally presents itself clinically as a painless, slowly enlarging nodular soft tissue mass that is usually present for some time before diagnosis. In 20% patients however, the lesion is painful and tender, especially if located on the plantar side of the foot . A case of a 49-year-old female was reported by Estil JC et al. , who had a slow-growing mass of 4 years duration, located on the plantar aspect of her left foot. The mass was slowly becoming more palpable as it increased in size and was progressively causing pain and discomfort during ambulation. Imaging studies revealed an ossified mass bearing no connection to any other structure on the plantar aspect of her foot. An excision biopsy was performed, and the easily dissectible mass, although much larger than its usual presentation, proved to be an extra skeletal osteochondroma. In 2015, Bilgin Y et al. , reported the case of a 56-year-old woman with an extra skeletal osteochondroma of the heel. In another case of slow-growing, relatively painful mass on the dorsal side of his right foot, in the 3rd toe web, reported by Kho et al.  found that an extraskeletal osteochondroma should be considered when a discrete, ossified mass is localized in the soft tissues of the distal extremities. Although cellular a typia is described on histological examination, there is no known malignant transformation or metastatic lesion. Marginal excision is the recommended treatment of choice, with preservation of the adjacent bone and soft tissue structures. A local recurrence rate of up to 18% has been reported, and such recurrence is best treated with re-excision.
In our present case of benign osteochondromatous lesion, the nodular mass was there beneath the 3rd MTP Joint. The clinic pathological and radiological features of our case excluded the likelihood of myositis, lipomatous lesion, tumoral calcinosis, ossifying fibro myxoid tumor, or malignancy which may present as discrete soft tissue masses. Although mature ossifications generally associated with a benign lesion, sarcomatous lesions such as synovial sarcomas, soft tissue chondrosarcoma and Osteosarcoma can also present with dense calcification and ossification . Thus, close histopathology and clinical correlations are essential to differentiate a chondrosarcoma from an extra skeletal osteochondroma.
In conclusion, an osteochondromatous lesion should be considered when a distinct, ossified mass is localized in the soft tissues of the distal extremities. It has been reported that they have low risk of malignant degeneration. Marginal excision is the recommended treatment, with preservation of the adjacent bone and soft tissue structures.