[Tumors of the foot skeleton]

[Foot and ankle tumours : Part I: overview of incidence, diagnosis and staging of pedal tumours]

CLINICAL ISSUE

Foot and ankle tumours are rare. Part I of this paper provides a survey about tumour distribution regarding age and location of benign and malignant bone and soft tissue tumours.

STANDARD RADIOLOGICAL METHODS

All diagnostic radiological procedures are used for the diagnostic work-up of pedal tumours, in particular plain radiography, MRI, and ultrasonography.

METHODICAL INNOVATIONS

Dual-energy CT proves to be a valuable (differential) diagnostic tool in identifying urate dihydrate crystals.

PERFORMANCE

There are no reliable numbers available on accuracy of the aforementioned diagnostic procedures regarding tumour detection and identification. This is particularly true for soft tissue tumours which are small and well-defined, thus requiring histological clarification.

ACHIEVEMENTS

To evaluate pedal tumours correctly and reasonably, a full range of radiological diagnostics should be employed. Neither plain radiography alone nor a stand-alone MRI examination-depending on the tumour site-are sufficient to characterize such tumours including staging.

PRACTICAL RECOMMENDATIONS

Plain radiography remains the first-choice imaging modality. Ultrasonography is superior to reliably detect and identify ganglion cysts. MRI, however, continues to remain the upmost diagnostic modality of choice for evaluating foot and ankle tumours. CT possesses unchallanged diagnostic power to assess osseous changes. Bone scintigraphy (including SPECT-CT) and FDG-PET imaging are used when multifocal distribution or metastatic disease are suspected or to detect avidity of the pedal lesions, respectively.

Do malignant bone tumors of the foot have a different biological behavior than sarcomas at other skeletal sites?

We analyze the delay in diagnosis and tumor size of malignant bone tumors of the foot in a retrospective study. We compared the oncological and surgical long-term results with identical tumor at other anatomical sites in order to analyze the biological behavior of sarcomas that are found in the foot. Thirty-two patients with a histologically proven malignant bone tumor (fifteen chondrosarcomas, nine osteosarcomas, and eight Ewing sarcomas) between the years 1969 and 2008 were included. The median follow-up was 11.9 years. The overall median time gap between the beginning of symptoms and diagnosis in the study group was 10 months. Ewing sarcoma presented with the longest delay in diagnosis (median of 18 months), followed by osteosarcoma (median of 15 months) and chondrosarcoma (median of 7.5 months). The delay in diagnosis of these tumors was significantly longer than that of equivalent tumors at other skeletal sites, but the 5- and 10-year survival rates and the occurrence of distant metastases were comparable. In contrast, the average size of foot tumors was 5- to 30-fold less than that of tumors analyzed at other skeletal sites. This study indicates that sarcomas of the foot demonstrate a distinct biological behavior compared to the same tumor types at other skeletal sites.