Precision genotyping diagnosis of lung tumors with trophoblastic morphology in young women

Trophoblastic differentiation has been previously described in somatic carcinomas at different primary sites, including the lung. Lung carcinomas with trophoblastic morphology presenting in women during the reproductive years pose a unique diagnostic challenge due to their overlapping microscopical and immunophenotypical features with metastatic choriocarcinoma of gestational origin. Distinction between the two entities is paramount as they require different chemotherapeutic regimens and have a markedly different prognostic outlook. Here we report a series of three female patients (ages 37-48 years) presenting with lung masses. Two of the three patients were noted to have elevated serum beta-hCG levels at the time of their presentation, while serum beta-hCG was not evaluated preoperatively in the third patient. None of them had a clinical history of molar pregnancy or gestational trophoblastic neoplasia. Core biopsies of the lung masses were performed in two patients and one patient underwent a wedge resection, showing poorly differentiated carcinoma in all cases with scattered multinucleated giant cells, hemorrhage, and necrosis. Beta-hCG immunostain was performed in two cases and showed diffuse immunoreactivity. Clinical history and imaging studies were not conclusive in any of the cases to rule out a gestational origin. Short tandem repeat genotyping analysis was performed to compare the allelic patterns between tumor and normal tissues and revealed identical profiles in one case, consistent with somatic origin, and unique paternal alleles in two cases, confirming metastatic gestational choriocarcinoma. The patient with primary somatic lung carcinoma died of disease within 15 months despite chemotherapy, while both patients with gestational choriocarcinoma responded well to chemotherapy and are alive without evidence of disease. Our cases illustrate the diagnostic pitfalls of lung tumors with trophoblastic differentiation in young women. Genotyping analysis offers precise diagnostic distinction between primary lung carcinoma and gestational choriocarcinoma with major therapeutic and prognostic implications for the patients.