An Interesting Case of Unknown Primary Presenting as Heel Pain

Sir,

A 64-year-old male presented with heel pain that had been present for past 3 months. An excision of the calcaneal lesion with bone cementing was performed which on histopathology revealed metastatic squamous cell carcinoma. Subsequent F-18fluorodeoxyglucose positron emission tomography/computerized tomography revealed increased tracer uptake in the left hemithorax, mediastinum on the right side, right scapula, right clavicle, pelvis and left distal extremity [Figure 1A] maximum intensity projection images]. Fused PET-CT with sagittal reformats [Figure 1B] of the left distal extremity reveals FDG avid skeletal lesions involving the remaining unexcised calcaneum, talus, navicular, cuneiform and proximal end of the metatarsals, distal end of femur and along the entire length of the tibia. Multiple skeletal lesions noted elsewhere in the body [Figure 1C]. Fused PET CT images [Figure 2A, B] revealed a tracer avid lesion in the lingular segment of the left lung with right lower paratracheal [Figure 2C] and contralateral lung metastasis [Figure 2D], suggesting primary in the left lung. CT-guided biopsy of the mass confirmed the squamous cell carcinoma lung.

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Figure 1 Fused PET-CT with sagittal reformats (B) of the left distal extremity reveals FDG avid skeletal lesions involving the remaining unexcised calcaneum, talus, navicular, cuneiform and proximal end of the metatarsals, distal end of femur and along the entire length of the tibia. Multiple skeletal lesions noted elsewhere in the body (C)

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Figure 2 Fused PET CT images (A, B) revealed a tracer avid lesion in the lingular segment of the left lung with right lower paratracheal (C) and contralateral lung metastasis (D)

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Plantar heel pain is a common complaint in this age group. In general, patients with bone metastases become symptomatic earlier in the clinical course than patients with liver and lung metastases. Obviously local symptoms alert clinicians to consider metastases. However, in some circumstances, they may have bizarre presentation.[123] Just like in this case, the patient presented with heel pain. There have been case reports of calcaneal metastasis in lung, gastric, urothelial and lung malignancies.[456] Thus, we need to ponder over the fact of acquiring vertex to toe images in certain clinical situations instead of the usual protocol. Also, the heel pain not responding to conservative therapy must be evaluated further.[Figure 1]: Fused PET-CT with sagittal reformats (B) of the left distal extremity reveals FDG avid skeletal lesions involving the remaining unexcised calcaneum, talus, navicular, cuneiform and proximal end of the metatarsals, distal end of femur and along the entire length of the tibia. Multiple skeletal lesions noted elsewhere in the body (C)[Figure 2]: Fused PET CT images (A, B) revealed a tracer avid lesion in the lingular segment of the left lung with right lower paratracheal (C) and contralateral lung metastasis (D)