Nasal seromucinous hamartoma (microglandular adenosis of the nose): a morphological and molecular study of five cases.

Five cases of nasal seromucinous hamartoma were studied and their clinical, morphological, immunohistochemical and molecular data are reported. The patients, three females and two males, ranged in age from 49 to 66 years (mean 56 year, SD ± 7.91). All lesions were located in the nasal cavity. In four cases where follow-up was obtained, no recurrence was evident. In all cases, numerous small seromucinous tubules, embedded in a cellular stroma, were present in the lamina propria. Tubules were lined by one layer of cuboidal cells which displayed luminal phenotype positive for lysozyme and EMA in four, and S100 protein in all cases. Collagen IV and laminin positive basal lamina outlined the tubules which lacked basal cells. Stromal spindle cells present among tubules were immunoreactive for calponin in all cases and for alpha-smooth muscle actin in four cases. DNA mutation analysis of mitochondrial D-loop region was performed by direct sequencing in order to verify the mutation rate of these lesions. The tubules of the five seromucinous hamartomas showed a higher mutation rate especially in heteroplasmy (0.52% homoplasmy, 2.02% heteroplasmy) in comparison to normal seromucinous glands which exhibited a lower mutation frequency (0.83%). This is considered a sign of a low cellular proliferation rate consistent with a benign process. It is concluded that nasal seromucinous hamartomas are benign glandular proliferations that may resemble microglandular adenosis of the breast. Their distinction from benign and malignant mimics is discussed.