Rapidly progressive bone destruction of the finger as first presentation of systemic metastases from lung cancer

Abstract

We report a case of a man with locally advanced lung adenocarcinoma and no evidence of metastatic disease presenting with rapid onset pain and swelling of his right second finger. Radiographically and clinically this was felt to be osteomyelitis and he was treated with intravenous antibiotics. He clinically worsened, and upon biopsy was found to have metastatic adenocarcinoma of the digit. He was treated with radiotherapy with some symptom improvement. He shortly thereafter developed diffuse skeletal metastases.

Background

Although metastasis to hands and feet are rare, they may present clinically like more common benign conditions, such as osteomyelitis, or rheumatologic processes. As such, they are clinically relevant for several medical specialties: primary care, oncology, dermatology, rheumatology, orthopaedic surgery, plastic surgery, and infectious diseases.

This case illustrates how diagnosis of metastases in digits can be difficult, and that misdiagnosis may lead to delays in patient management and symptom resolution.

Case presentation

A middle aged man was referred to our department for management of his newly diagnosed locally advanced lung adenocarcinoma.

Previous medical history was significant only for lower back injury, remote history of alcohol abuse, and a 40+ pack-year smoking history resulting in chronic obstructive pulmonary disease (COPD). Family history was non-contributory for malignancy.

At his initial clinic visit he presented with significant respiratory symptoms related to the tumour and post-obstructive pneumonia, including fever and chills, cough, production of purulent sputum, and an elevated white blood cell count. Recent staging investigations including a computed tomography (CT) scan of the brain and abdomen/pelvis and bone scan revealed no evidence of metastatic disease. Because of his poor performance status (ECOG 3), significant weight loss and extensive thoracic disease, he was determined not to be a candidate for curative combined chemotherapy and radiation. He was treated with ciprofloxacin and clindamycin for his pneumonia and with 10 fractions of moderate dose palliative radiotherapy for his thoracic disease.

On follow-up 10 days after completion of radiotherapy, his pulmonary symptoms had improved with resolution in his cough, sputum production and fever. However, he reported the presence of some pain in his right second finger. Physical examination revealed a mildly tender, non-erythematous finger with mild swelling and decrease in range of motion. Hand x-ray (fig 1) demonstrated only mild soft tissue swelling. He was scheduled for a follow-up in 4 weeks, with instructions to seek medical attention if the finger became inflamed or he developed a fever.

Figure 1.

Plain x-ray taken at initial complaint of finger pain.

The patient’s finger became progressively swollen over the ensuing weeks, and he was started on cephalexin 500 mg four times daily by his family physician for presumed cellulitis. At his 1 month clinic appointment, the finger was notably swollen, erythematous and tender. An x-ray (fig 2) showed an aggressive, focal destructive process at the base of the proximal phalanx of the second digit. Given the sudden progression and history of recent significant pulmonary infection, the patient was seen by an infectious diseases specialist and referred to plastic surgery with a presumptive diagnosis of osteomyelitis. A small volume joint aspirate was performed which was non-diagnostic for infection. He was admitted to hospital and treated with intravenous vancomycin/cefazolin/ciprofloxacin. His symptoms improved dramatically and he was discharged home after 5 days on oral antibiotics.

Figure 2.

Plain x-ray taken at 4 week follow-up. Red arrowhead indicates proximal phalanx destruction; blue arrowhead demonstrates joint space preservation.

Despite initial improvement with antibiotics, in clinic 3 weeks later the entire finger was now swollen and exquisitely painful despite use of narcotics for pain control. An x-ray (fig 3) showed pronounced progression of the destructive bony lesion, extending to the head of the proximal phalanx with intact subchondral bone at the base of the finger and preservation of the joint space. A biopsy was performed which revealed adenocarcinoma consistent with metastasis from his lung primary tumour.

Figure 3.

Plain x-ray taken at 7 weeks. Red arrowhead indicates further destruction of the head of the proximal phalanx; blue arrowhead demonstrates joint space preservation.

Differential diagnosis

• Working diagnosis: osteomyelitis

• Differential diagnosis: septic arthritis, metastatic adenocarcinoma.

Treatment

Once the diagnosis of metastatic adenocarcinoma was made, the patient was given a single 8 Gy fraction of radiotherapy for pain control, with excellent results.

Outcome and follow-up

The patient was admitted to hospital for pain control while he received his palliative radiotherapy to the finger. During his admission he reported new painful areas in his legs and back. Unfortunately, a repeat bone scan revealed diffuse bony metastatic disease not seen on the initial bone scan at time of diagnosis. He received palliative radiotherapy to the symptomatic sites, and was referred for palliative care management.

Discussion

Metastases to the hand or foot (acrometastases) are rare, representing only 0.1% of all skeletal metastases.¹ Most common primary tumours with spread to the hand are lung (40%), kidney (14%) and breast (10%), although there are several case reports of acrometastasis from multiple primary tumour sites.² The distal phalanges are the most common affected bones, although all bones in the hand and wrist may be affected.^1–3

Clinical diagnosis can be difficult. Presenting complaints of pain, swelling, erythema and inability to move joints may mimic much more common diagnoses such as osteomyelitis, gout, septic arthritis or other infectious/rheumatologic/dermatologic conditions, as supported by several case studies. Radiographically, lesions tend to be osteolytic, and tend not to cross joint spaces or develop a periosteal reaction⁴. Although positron emission tomography (PET) does have utility in diagnosing metastatic disease, it is not specific enough to discriminate between malignancy, inflammation or infection.⁵

Treatment of hand metastasis is dependent on the functional status of the patient, and the extent of the metastatic disease. Hand metastases predict for poor prognosis, as they are associated with diffuse metastatic disease.^6,7 Generally, treatment (surgery, radiation or chemotherapy) is focused on symptom control and maintenance of functional capacity.⁸

Our patient’s history of bacterial pneumonia and the rapidity of bony destruction, in conjunction with the recent staging investigations that did not reveal presence of any metastatic disease, favoured a diagnosis of osteomyelitis. However, the preservation of joint space on serial imaging and initial non-diagnostic joint aspiration were clues of metastatic disease.

This case illustrates that diagnosis of acrometastases can be challenging. It demonstrates the importance of maintaining metastatic disease in the differential when evaluating patients with a non-specific clinical presentation. Close attention must be paid to subtleties in imaging, and ultimately, pathologic confirmation is essential.

Learning points

• Metastases to digits are rare.

• The diagnosis of digital metastasis may be difficult as symptoms mimic more common aetiologies (infectious or rheumatologic). Joint space preservation is commonly seen with metastases.

• Even in the setting of no known metastatic disease and rapidly progressive symptoms suggestive of other aetiologies, the diagnosis of acrometastasis must be considered and a biopsy is required.