Answer: Metastatic prostatic adenocarcinoma

Histologic Description: This is a bland tubular proliferation which irregularly infiltrates the peribronchial soft tissue. The bland chromatin of the cells suggest the possibility of a neuroendocrine neoplasm, but the architecture is far more tubular than nested. The cytology is far blander than any typical adenocarcinoma of the lung. The glands permeate the fat irregularly, which would be unusual for peribronchial glands which are lobular in their configuration. On further inquiry, this patient had a history of prostatic adenocarcinoma, and the current glands labeled PSA and NKX3.1, supporting the diagnosis.

Differential Diagnosis: Peribronchial glands would be more lobular in their configuration, and typically centered in the bronchial wall submucosa. Adenocarcinoma of the lung demonstrates more cytologic atypia than the bland glands of the current case. Carcinoid tumor is a serious consideration, given the bland cytology of the cells. Carcinoid tumors may demonstrate predominant tubular architecture; however, they should label for neuroendocrine markers and have more salt and pepper type chromatin. The diffuse labeling for prostatic markers along with the history in this case supports the diagnosis of metastatic prostatic adenocarcinoma.