Approach to Painful Subcutaneous Nodules
Initial Diagnostic Evaluation
The diagnostic approach to painful subcutaneous nodules should follow a systematic process of clinical assessment, imaging, and when necessary, tissue sampling to determine the underlying etiology and guide appropriate treatment.
Clinical Assessment
- Evaluate for infectious causes such as leishmaniasis, which may present with subcutaneous nodules, especially in endemic areas or in travelers 1
- Consider gnathostomiasis in patients with recurrent pruritic or painful, ill-defined migratory subcutaneous nodules, particularly with relevant travel history 1
- Assess for systemic diseases that commonly present with subcutaneous nodules, including sarcoidosis, inflammatory bowel disease, and rheumatoid arthritis 2
- Document nodule characteristics including size, consistency, mobility, tenderness, and relationship to surrounding structures 3
Imaging Evaluation
- Ultrasonography is the first-line imaging modality for subcutaneous nodules, allowing characterization based on echogenicity patterns 3
- Tophi appear as heterogeneous masses, sometimes with calcifications
- Rheumatoid nodules appear more homogeneous with possible central hypoechoic areas
- Lipomas show well-demarcated capsules with variable echogenicity
- Synovial cysts demonstrate characteristic hypoechoic patterns 3
- For nodules suspicious for malignancy, CT scans with thin sections (≤1.5 mm) should be performed for accurate characterization 4
- For multiple nodules or suspected metastatic disease, follow a risk-stratified approach based on nodule size and characteristics 4
Diagnostic Procedures
Biopsy Considerations
- Perform tissue sampling for nodules of uncertain etiology, as biopsy results will alter management 4
- For suspected infectious etiologies like leishmaniasis, tissue aspirates or biopsy specimens should be collected for smears, histopathology, parasite culture, and molecular testing 1
- Consider fine-needle aspiration cytology (FNAC) as an initial, less invasive diagnostic approach 5
- For definitive diagnosis, excisional or incisional biopsy may be necessary 1
Management Based on Etiology
Infectious Causes
- For leishmaniasis with subcutaneous nodules:
- For gnathostomiasis:
- Ivermectin 200 μg/kg daily for 2 days is recommended with monitoring for relapse
- Alternative treatment is albendazole 400 mg twice daily for 21 days 1
Inflammatory/Autoimmune Causes
- For rheumatoid nodules:
- For sarcoidosis presenting with subcutaneous nodules:
- Steroid treatment has shown satisfactory response 7
Malignant Causes
- For nodules suspicious for malignancy:
- Low risk (<10% probability): surveillance is recommended
- Intermediate risk (10-70%): consider PET-CT for further assessment
- High risk (>70%): consider excision or non-surgical treatment 4
Special Considerations
Pain Management
- Nonsteroidal anti-inflammatory drugs (NSAIDs) can be used for pain control in inflammatory conditions like erythema nodosum 2
- For painful nodules due to leishmaniasis, local anesthesia should be given in advance of any intralesional treatment 1
Follow-up Recommendations
- Serial ultrasonography can be used to monitor changes in nodule size and characteristics over time 3
- For infectious causes, follow-up should continue until complete resolution of the nodules 1
- For nodules associated with systemic diseases, monitor for disease activity and treatment response 2
Pitfalls to Avoid
- Do not rely solely on clinical appearance for diagnosis, as various etiologies can present with similar-appearing nodules 3
- Avoid intralesional injections in certain anatomical locations (fingers, nose, ears, eyelids, near lips) where vascular compromise could occur 1
- The negative predictive value of a biopsy is greatest when the pre-test probability of malignancy is low; false negatives can occur 4
- Do not treat solely with physical methods (like cryotherapy) if there is evidence of potential dissemination of infection 1