Tumorlets: Tumorlets are nodular proliferations of neuroendocrine cells that are normally present in the airways. In the neonate, neuroendocrine (Kulchitsky) cells are present frequently as single cells or clusters in the epithelium. They become less frequent with age. In certain lung diseases--cystic fibrosis, asthma, COPD, eosinophilic granuloma, and primary pulmonary hypertension--these cells sometimes become hyperplastic for unknown reasons. Tumorlets are nodular proliferations up to 4 mm in diameter in the airway wall. (Larger tumors are called carcinoids.) Tumorlets are common incidental findings in lungs scarred by chronic bronchitis or bronchiectasis [1,2], but they may also be found in otherwise normal lungs [1]. Often multiple, and usually peripheral, they are characterized by small nests of cells having neurosecretory granules. They lack mitoses and cellular atypia. Typically, they have a hyalinized, fibroelastic stroma [1]. Lymph node metastases have been noted in 4 or 5 cases. One case that was associated with Cushing's syndrome had tumor that metastasized widely [3]. In 36 cases, females predominated, 28 to 8, and the average age was 70 [1].

Figure: This lesion was an incidental postmortem finding in a 69-year-old man. A tumorlet fills or lines several air spaces. Note the fibrous response that was not present elsewhere in this man's lung. The lack of attachment of the tumor cells is a postmortem artifact. At higher magnification (below), peripheral palisading of cells is seen. The tumor cells have stippled chromatin, and mitoses are absent.

Authors of a recent report have proposed that in patients with innumerable tumorlets, they are the cause, rather than the result, of an obstructive/restrictive lung disease. Seven patients described have had complaints of chronic cough and dyspnea. Chest radiographs showed diffuse reticulonodular opacities [4,5].


1. Churg A, Warnock M. Pulmonary tumorlet. A form of peripheral carcinoid. Cancer 1976; 37:1469-1477.

2. Pelosi G, Zancanaro C, Sbabo L, Bresaola E, Martignoni G, Bontempini L. Development of innumerable neuroendocrine tumorlets in pulmonary lobe scarred by intralobar sequestration. Immunohistochemical and ultrastructural study of an unusual case. Arch Pathol Lab Med 1992; 116:1167-1174.

3. D'Agati V, Perzin K. Carcinoid tumorlets of the lung with metastasis to a peribronchial lymph node. Report of a case and review of the literature. Cancer 1985; 55:2472-2476.

4. Miller M, Mark G, Kanarek D. Multiple peripheral pulmonary carcinoids and tumorlets of carcinoid type, with restrictive and obstructive lung disease. Am J Med 1978; 65:373-378.

5. Aguayo S, Miller Y, Waldron J Jr, Bogin R, Sunday M, Staton G Jr, Beam W, et al. Idiopathic diffuse hyperplasia of pulmonary neuroendocrine cells and airways disease. N Engl J Med 1992; 327:1285-1288.


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