Minute meningothelial-like nodules (MMLNs), previously called chemodectomas, are common, tiny, incidental interstitial nodular proliferations. MMLNs have diameters up to 1 to 3 mm. They may appear as grayish-tan nodules in the lung, including subpleurally. Both monoclonality and polyclonality have been demonstrated in MMLNs. It is not certain whether they are reactive or neoplastic, although investigators favor the former. Simultaneous occurrence of primary meningioma of the lung (see Chapter 24, Part 4, Subpart 4.5) and multiple MMLNs has been reported, and a possible pathogenetic relationship has been suggested. Differential diagnosis includes carcinoid tumorlet, metastatic carcinoma, interstitial fibrosis, and granuloma.