1 Introduction

Extraskeletal myxoid chondrosarcoma (EMC) is a rare soft tissue neoplasm. In 1972, Enzinger and Shiraki recognized EMC as a distinct entity that develops in soft tissues, but with histology similar to that of chondrosarcoma of the bones.¹ In 1992, Saleh et al. reassessed the clinical features of EMC in a series of 10 patients and depicted the “indolent but resilient” nature of this neoplasm.²

This case report was prepared following the CARE guidelines.³

From our extensive Pubmed research, we have found that only 14 cases of extraskeletal myxoid chondrosarcoma involving foot have been reported with relevant data such as clinical presentation, modality of treatment, follow-up, and survivorship. From our knowledge, this is the first reported case of EMC arising from foot in the Indian population.

Through this case report, we present challenges faced during its treatment and review of cases published in past.

2 Case report

A 46-year-old male, jeweler by profession, presented to our clinic with a 5-month-old history of painful swelling over the plantar aspect of the left foot. Over the past 5 months, the swelling had increased in size & the patient had started experiencing pain while prolonged standing and walking. The patient was diabetic & hypertensive for 5 years. The patient was vegetarian by diet, alcoholic, non-smoker, and consumed pan masala (mixture of areca nut & tobacco) for 20 years. A thorough clinical examination was done which revealed an 8 cm sized firm, fixed swelling over the plantar aspect of the left foot which wasn't of bony origin [Fig. 1].

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Fig. 1 Clinical picture depicting appearance of the lesion.

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An MRI was performed which revealed an altered signal intensity lesion measuring 8.3 ​× ​3.1 ​× ​2.7 cm along the plantar aspect of foot deep to central band of plantar fascia extending from mid calcaneum to mid shaft of 2nd metatarsal, involving the flexor digitorum brevis muscle & was significantly hyperintense on T2/STIR images [Fig. 2]. Further, chest Xray & blood tests were done which came out to be normal.

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Fig. 2 T2 weighted MRI showing hyperintense lesion extending from mid calcaneum to mid shaft of 2nd metatarsal.

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Ultrasonography-guided Tru-cut biopsy was performed by an interventional radiologist which revealed round to oval tumor cells arranged in streaks and small groups in the prominent myxoid background with minimal anaplasia and negligible mitotic activity. Because of the rarity of the tumor, one of the consulting oncologists recommended getting a repeat biopsy for confirmation of diagnosis. But to avoid an extra invasive procedure we planned to go with definitive surgery with options of wide excision and marginal excision in mind.

Intraoperatively decision of wide excision of the lesion was made & 10 ​× ​4 ​× ​3 cm grayish brown, firm, granular lesion was removed [Fig. 3] and sent for histopathological & immunohistochemistry studies. Immunohistochemistry studies revealed that tumor cells were positive for S-100, NSE & Synaptophysin and were negative for Pan-CK. The histopathological report was consistent with the diagnosis of extraskeletal myxoid chondrosarcoma & margins were negative for tumor cells.

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Fig. 3 Intraoperative picture depicting gross appearance of the widely excised tumor.

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Postoperatively patient had a complaint of blood-stained discharge from the surgical site for which USG guided repeat FNAC was done which came out to be negative for tumor cells. The patient's wound became dry and healed after repeated dressings. The patient had not undergone chemotherapy or radiotherapy. FDG PET scan was performed showing no evidence of metastatic spread. After 7 months of surgery, the patient is good clinical state and there is no evidence of distant metastasis in the monthly follow-up.

3 Discussion

EMC is a rare soft tissue sarcoma having a high risk of local recurrence and distant metastasis.¹

EMC occurs commonly in middle-aged men,⁴ which was also seen in our case report. It usually affects proximal extremities,⁴ while the foot is a rare location of occurrence of this neoplasm. Two cases of plantar foot lesions have been reported where EMC was confused with plantar fibroma.^5,6 Prognosis of plantar fibroma and EMC are contrasting; therefore, differential diagnosis of EMC should be kept in mind while dealing with soft tissue tumors affecting the plantar aspect of the foot.

The rare occurrence of this tumor and limited research data available was a major challenge while planning definitive treatment of the patient. Among 14 adequately documented cases of EMC affecting the foot in past studies, 9 patients were treated with amputation, 4 were treated with wide excision & 1 with chemotherapy^1,2,6–11 [Table 1]. Results of chemotherapy for treating EMC in past studies were not satisfying.²

A similar case of a 39-year-old male with EMC affecting plantar aspect of foot but with a smaller size of approx. 5.3 ​× ​3.4 ​× ​3 cm has been reported by CC Gala et al. in which amputation was the modality of treatment & the patient was reported to be alive and disease-free in 4 months of follow-up.⁶

Considering the lack of evidence regarding the superiority of amputation over wide excision; we performed wide excision of the tumor. Intraoperatively, we faced a major challenge in determining the proximal extent of the tumor. We suggest that intraoperative use of ultrasonography to assess the proximal extension of tumor in affected structure could be a useful aid in surgeries of soft tissue sarcoma.

Due to the wide excision of the tumor, large dead space was created in the foot [Fig. 4] which caused blood-stained discharge and soakage postoperatively. There are chances of marginal skin necrosis in such cases. Therefore, we recommend a plastic surgeon's opinion before excising large tumors of the plantar aspect of the foot to decrease wound-related complications.

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Fig. 4 Intraoperative picture depicting dead space created on the plantar aspect of the foot following wide excision of the tumor.

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As after 7 months of follow-up, the patient has remained disease-free, we would recommend wide excision of EMC over amputation as the preferred modality of treatment. We are currently awaiting long-term results to verify whether or not the patient continues to be disease-free.

However, the results of a single case may not apply to all patients in general. The short duration of follow-up (7 months) is also a major limitation of our study. Thus, long-term studies with more subjects and longer periods of follow-up may be required to consolidate to a concrete conclusion.

4 Patient's perspective

I found a swelling in my left foot due to which I had pain while walking. So, I consulted my doctor and was surprised to know that this could be a malignant tumor. Following his advice, I got my MRI and biopsy done. I got worried after knowing that my investigations are in favor of a rare malignant tumor. After consulting him, I got my surgery planned. I am mentally relaxed after my surgery and after knowing that there is no distant spread on the PET scan report. I am back to my routine activities. I was informed of the high recurrence rate of this tumor therefore; I am regular on my follow-up. I am thankful to my doctors for guiding me and treating this rare tumor with great coordination.

Declaration of interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Consent

Informed consent was obtained from the patient included in this study.

Financial disclosure

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Conflict of interest

The authors declare that there are no potential conflicts of interest concerning the research, authorship, and/or publication of this article.

CRediT authorship contribution statement

Siddharth Jain: Conceptualization, Writing – Original draft, Investigation. Pankaj Jain: Data curation, Visualization. Sonal Mishra: Investigation.