Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is regarded as a precursor to the development of carcinoid tumorlets. It is confined to the neuroendocrine cell of the airway mucosa without penetration through the basement membrane and appears in a diffuse pattern, typically in association with obliterative bronchiolar fibrosis. DIPNECH belongs to the preinvasive lesions defined by the 1999 World Health Organization classification, along with atypical adematous hyperplasia and squamous dysplasia carcinoma in situ.
A 58-year-old lady, with a background of Dukes A Carcinoma Colon resected 14 years previously, was referred with symptomatic primary hyperparathyroidism and was subsequently found to have a two gland parathyroid hyperplasia on open neck exploration. She underwent subsequent imaging and biochemical tests to exclude Multiple Endocrine Neoplasia Type 1. These revealed a raised Somatostain level on fasting gut hormone profile and a 4.3 cm lesion in the right middle lobe of lung along with multiple lung nodularities on thoracoabominal CT scanning. A CT guided biopsy of the 4.3 cm lesion revealed the presence of neuroendocine cells suggestive of carcinoid with concordance of the large lesion on Octreotide and MIBG scanning. No evidence of metastasis was revealed on PETCT.
She subsequently underwent a middle and lower lobectomy and histology confirmed that the lesion to be a central thoracic carcinoid. The rest of the lung showed diffuse multiple foci of neurodendocrine tumourlets and multiple small carcinoids (DIPNECH) throughout with evidence of pulmonary thrombotic veno-occlusive phenomenon. It was felt that the central carcinoid was an independent finding with the surrounding DIPNECH being secondary to veno-occlusive disease.
A review of the literature suggests that DIPNECH is associated with peripheral sub-clinical carcinoid formation but does not lead to development of central bronchial carcinoids. DIPNECH neuroendocrine cells usually do not lead to clinically significant endocrinopathies and are in general an incidental finding. This case therefore highlights two seemingly unrelated rare pathologies.