Hepatoid Adenocarcinoma of the Lung Accompanied with Multiple Systemic Metastases
Hepatoid adenocarcinoma of the lung (HAL) is an extraordinarily rare and aggressive malignancy characterized by its morphological resemblance to hepatocellular carcinoma (HCC) and frequent association with alpha-fetoprotein (AFP) production. This tumor variant, first described by Ishikura et al. in 1990, remains poorly understood due to its scarcity and diagnostic complexity. The following comprehensive review synthesizes the clinical, pathological, and therapeutic insights from a recent case study of HAL with systemic metastases, while contextualizing the findings within the broader medical literature.
Clinical Presentation and Diagnostic Evaluation
The case involved a 63-year-old male patient with no prior history of hepatitis, liver disease, or significant medical conditions. Initial symptoms included diffuse, migratory lumbar soreness and pain, exacerbated in the afternoon and temporarily alleviated by ibuprofen. Over one month, the patient developed 6–7 subcutaneous nodules measuring 1–2 cm in diameter across the lumbar, dorsal, abdominal, and precordial regions. These nodules were mobile, non-ulcerated, and partially tender, lacking signs of inflammation.
Laboratory investigations revealed marked abnormalities: leukocytosis (11.07 × 10⁹/L), anemia (hemoglobin 95 g/L), thrombocytosis (436 × 10⁹/L), and elevated liver enzymes (alanine aminotransferase: 68 U/L). Tumor marker profiling showed extreme elevations in carcinoembryonic antigen (CEA >100 ng/mL), carbohydrate antigen 72-4 (CA 72-4 >300 U/mL), and cytokeratin-19 fragment (Cyfra21-1: 31.8 ng/mL). Notably, AFP levels—a hallmark of hepatoid differentiation—were not explicitly reported, aligning with revised diagnostic criteria that no longer mandate AFP positivity for HAL diagnosis.
Histopathological examination of resected subcutaneous nodules revealed poorly differentiated adenocarcinoma with hepatoid features, including trabecular growth patterns and polygonal cells resembling hepatocytes (Figure 1A). Immunohistochemical staining further supported hepatoid differentiation, though specific markers were not detailed in the report. Positron emission tomography/computed tomography (PET/CT) identified a primary soft-tissue mass in the left lung apex, a right upper lobe nodule abutting the pleura, and widespread metastatic lesions in lymph nodes, soft tissues, and subcutaneous regions (Figure 1B).
Disease Progression and Outcome
Despite prompt diagnostic intervention, the patient’s condition deteriorated rapidly. Systemic metastases implicated multiple organs, consistent with the aggressive biology of HAL. No surgical resection of the primary lung tumor was attempted, likely due to advanced disease staging. The patient succumbed to multiple organ failure within four months of initial diagnosis, underscoring the dismal prognosis associated with advanced HAL.
Pathological and Diagnostic Considerations
HAL belongs to the broader category of hepatoid adenocarcinomas (HACs), which most frequently arise in the stomach (63% of cases) but may occur in extra-gastrointestinal sites, including the lungs. The diagnostic criteria for HAL have evolved since Ishikura’s original description. Haninger et al. (2014) refined these criteria to include AFP-negative cases, emphasizing morphological mimicry of HCC over obligate AFP expression. This shift acknowledges the biological heterogeneity of HAL and reduces diagnostic oversight of AFP-negative variants.
Key histological features include glandular or papillary structures coexisting with hepatoid components. Immunohistochemical markers such as HepPar-1, arginase-1, and AFP may aid differentiation from metastatic HCC, though overlap exists. In this case, the absence of hepatitis history and primary liver lesions helped exclude metastatic HCC, reinforcing the diagnosis of primary HAL.
Therapeutic Challenges and Prognostic Factors
Treatment strategies for HAL mirror those for non-small cell lung cancer (NSCLC), with surgical resection offering the best outcomes for localized disease (Stage I-II). However, most patients present with advanced-stage HAL (Stage III-IV), as seen in this case, where surgery is contraindicated. Palliative chemotherapy and radiotherapy provide limited benefit, with median survival often measured in months.
Prognostic determinants include tumor stage, AFP levels, and metastatic burden. Elevated CEA and CA 72-4, as observed here, correlate with aggressive behavior and poor survival. The rapid progression from symptom onset to death in this patient highlights the critical need for early detection and novel therapies.
Epidemiological and Etiological Insights
HAL predominantly affects elderly males, frequently with a smoking history, though the patient in this case had no reported tobacco use. The pathogenesis remains obscure, with no clear association with hepatitis viruses or cirrhosis. Molecular studies suggest genetic aberrations distinct from conventional NSCLC, but comprehensive genomic profiling of HAL is lacking.
Clinical Implications and Future Directions
This case illustrates the diagnostic challenges posed by HAL, particularly its mimicry of HCC and the potential for unusual metastatic patterns (e.g., subcutaneous nodules). Clinicians should consider HAL in patients with lung masses and hepatoid histology, even in the absence of AFP elevation.
Future research must prioritize molecular characterization of HAL to identify targetable pathways. Additionally, standardized reporting of cases and multicenter collaborations could enhance understanding of incidence, optimal treatment protocols, and prognostic markers.
Conclusion
Hepatoid adenocarcinoma of the lung represents a diagnostically and therapeutically challenging malignancy with a propensity for early systemic dissemination. This case underscores the importance of integrating clinical, histopathological, and imaging data to differentiate HAL from metastatic HCC and other mimics. While current therapeutic options remain inadequate, early recognition and radical resection may improve outcomes in localized disease. The relentless progression observed in advanced cases necessitates urgent exploration of novel treatment modalities.
DOI: 10.1097/CM9.0000000000000963
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