Multifocal micronodular pneumocyte hyperplasia in a patient with undiagnosed tuberous sclerosis: next-generation sequencing of a lung biopsy reveals TSC1 mutation-a case report.

backgroundMultifocal micronodular pneumocyte hyperplasia as first manifestation of tuberous sclerosis complex has rarely been reported. CASE PRESENTATION: We report a case of a 50-year-old white, non-Hispanic or Latino, female with no prior history of tuberous sclerosis complex who presented with nonspecific symptoms. Chest computed tomography showed multiple bilateral ground-glass lung nodules, ranging from 4 to 7 mm. Wedge biopsies led to a histological differential diagnosis of atypical adenomatous hyperplasia and multifocal micronodular pneumocyte hyperplasia. Some of the lesions were then micro-dissected and molecular studies revealed a pathogenic TSC1 mutation and loss of heterozygosity of the TSC1 gene. In the absence of adenomatous hyperplasia driver mutations, these findings were consistent with the diagnosis of multifocal micronodular pneumocyte hyperplasia. Follow-up blood work revealed mosaicism for the TSC1 mutation, meeting diagnostic criteria for tuberous sclerosis complex.

conclusionOur report suggests that multifocal micronodular pneumocyte hyperplasia should be considered in the differential diagnosis of bilateral, small ground-glass nodules and molecular testing may be useful to confirm the diagnosis.