A rare case of pulmonary typical carcinoid with prominent acinic cell differentiation, resembling acinic cell carcinoma

Abstract

We herein describe a rare case of low‐grade endobronchial tumor that exhibited two distinct features of typical carcinoid and acinic cell carcinoma (ACC) by immunohistochemical and ultrastructure study. ACC was suspected on transbronchial biopsy. The resected specimen showed that the tumor surface comprised an acinic cell component (40% of the tumor), and the central area comprised typical carcinoid (60% of the tumor). The acinic cell component was positive for chromogranin A, synaptophysin and alpha‐1‐antichymotrypsin. Additionally, this component showed focal apical membranous staining for DOG1 and weak positivity for BCL10 and SOX10. Conversely, the carcinoid component was negative for all proteins except for chromogranin A and synaptophysin. Electron microscopy indicated zymogen‐type granules (600–800 nm in diameter) in the acinic cell component, whereas neuroendocrine‐type granules (200–300 nm in diameter) were observed in the carcinoid component. Nuclear NR4A3 immunostaining, which is highly specific for ACC of the salivary gland, was negative in this case. We conclude that the pulmonary carcinoid tumor with true zymogen‐type granules could be seen but showed superficial similarities to ACC based on negative nuclear staining for NR4A3. Pulmonary carcinoids encompass a wide morphological spectrum and may exhibit prominent acinic cell differentiation.

Recent developments in the pathology of primary pulmonary salivary gland‐type tumours

“…171 NR4A3 rearrangement was not identified by FISH in the one tested case of pulmonary AciCC. 16 NR4A3 immunohistochemistry was negative in a combined AciCC/carcinoid tumour, 178 and was not performed on any of the reported pure AciCC of the lung.…”

“…[16][17][18][19]179 A panel of immunostains for distinguishing AciCC from histologically similar entities in the lung may therefore include TTF-1 (to exclude lung adenocarcinoma), p63 (to exclude HCCC and MEC), and mammaglobin and S100 protein (to exclude secretory carcinoma). 18 Four cases of AciCC were reported to be combined with carcinoid tumour 178,[180][181][182] ; all showed neuroendocrine marker staining including in the AciCC component, 178,[180][181][182] in contrast to lack of expression of neuroendocrine markers in pure AciCCs of the lung. [16][17][18][19]47,[159][160][161]165,166,179 Pulmonary AciCC tends to behave less aggressively than other pulmonary carcinomas.…”

Prognostic factors and survival outcome of primary pulmonary acinar cell carcinoma

“… 2 PACC was first introduced in 1972 and has been widely recognized since then. 3 To diagnose the tumor, the pathologists investigate the carcinoma cells microscopically. Subtypes are indicated according to the observation of the primary pathological pattern of histology.…”