Keywords
18F-fluorodeoxyglucose - bone metastasis - lung cancer - osteoarthritis - positron emission
tomography–computed tomography
Introduction
The skeleton is the most common site of metastasis in patients with lung cancer (about
10% of patients surgically treated in Stages 1 and 2). Early localization of metastatic
bone lesions is crucial for improving patient prognosis and determining the therapeutic
plan.[1] Metastasis to the hand is extremely rare, with an incidence of 0.1% reported in
the literature.[2] It is associated with a poor prognosis with a median survival following the development
of symptomatic hand metastasis reported about 6 months. Skeletal muscle metastases
from non-small cell lung cancer are also rarely encountered in clinical practice.[3] The role of 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography–computed tomography (PET/CT) in the diagnosis,
staging, and monitoring of lung cancer is well established. Today, the clinical utility
of PET scan is expanding in the diagnosis of many inflammatory conditions, such as
osteomyelitis, because of its ability to depict FDG uptake due to enhanced glycolytic
metabolism in inflammatory cellular infiltrates.[4] Here, we describe a case of occult lung cancer presenting as metastatic disease
to the finger.
Case Report
A 53-year-old right-handed man was admitted to our hospital with an intense pain on
his distal phalanx of the left hand's first finger. His medical history revealed only
diabetes mellitus. The finger was swollen, and hyperemic and radiographic evaluation
showed a fracture of the distal phalanx with soft-tissue radiolucent areas related
to osteomyelitis. After 2 months of unremitting finger pain treated with antibiotic
and anti-inflammatory therapy, a tru-cut biopsy was performed. Poorly differentiated
squamous carcinoma was determined with biopsy. Therefore, the patient underwent total
body PET/CT and chest CT evaluations. PET/CT showed a hypermetabolic left lower lobe
lung mass (SUVmax = 12.5) without mediastinal adenopathy [Figure 1]. Bone metastases were also revealed in the spine (SUVmax = 16.4), in the skull (SUVmax = 14.9), and in the distal phalanx of the left hand's first finger (SUVmax = 7.1) [Figure 2], [Figure 3]. In addition, areas of FDG focal uptake have also been detected in some muscle bundles,
such as right trapeze muscles, external and internal intercostal muscles of the left
hemithorax, left gluteus, and in several groups, posterior muscle of both thighs,
mostly right (SUVmax 12.5) [Figure 4]. These areas are suggestive for skeletal muscle metastases. High-resolution CT scan
of the chest confirmed extensive thickening of the lung parenchyma in the left parahilary
site and the absence of pathological lymph nodes affecting the chest. Only after these
diagnostic evaluations, the patient presented dyspnea and cough exacerbated by deep
breathing. Biopsy during bronchoscopy confirmed the diagnosis of poorly differentiated
squamous cell carcinoma. To exclude infectious or abscess areas, a magnetic resonance
imaging (MRI) was also performed which confirmed the presence of bone lesions related
to metastasis in the same locations of the spine and skull revealed by PET/CT. The
patient was then subjected to finger surgery and chemotherapy associated with radiation
therapy.
Figure 1 Transaxial positron emission tomography-computed tomography slice showing area of
increased 18F-fluorodeoxyglucose uptake of the left lower lobe lung mass without mediastinal adenopathy
Figure 2 Transaxial positron emission tomography-computed tomography images of the distal
portion of the left hand showing hypermetabolic area of the distal phalanx of the
first finger (red arrow)
Figure 3 Positron emission tomography-computed tomography images showing sacral bone metastasis,
with high-level glucose uptake
Figure 4 Sagittal positron emission tomography-computed tomography slices demonstrating areas
of fluorodeoxyglucose focal uptake in some muscle bundles, like right trapezius muscles,
intercostal muscles of the left hemithorax, left gluteus, and in several groups of
posterior muscles of both thighs
Discussion
Acral metastasis is usually associated with advanced lung cancer and very rarely can
be the first sign of the carcinoma.[5],[6] It is usually a poor prognostic sign and most commonly on the dominant hand and
distal phalanx. Since in our case the patient was right-handed and diabetic, the painful
symptoms were underestimated due to microangiopathy and peripheral neuropathy but
also due to the lower use compared to the contralateral hand. It can also mimic infection
or inflammatory disease. According to literature data, 18F-FDG PET/CT is more accurate than MRI and bone scintigraphy for bone metastasis in
patients with lung cancer, even in hand district, and in the skeletal muscle system.
Surgical treatment on acral metastasis does not extend the expectancy of life, but
it reduces the patient's pain during his terminal period.
Conclusion
It is now established that 18F-FDG PET/CT alone has better diagnostic value for diagnosing bone metastases from
lung cancer than any other imaging method (high-resolution computed tomography, MRI,
and X-rays).[1] Our case shows that PET is able to provide a complete whole-body staging and has
therefore been decisive in the diagnosis that the other methods have only been able
to confirm targeted segments.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form, the legal guardian has given his consent for images and other clinical
information to be reported in the journal. The guardian understands that names and
initials will not be published and due efforts will be made to conceal identity, but
anonymity cannot be guaranteed.
