Sclerosing pneumocytoma: a host for a typical carcinoid with pleural metastasis – a wolf in sheep's clothing

Background:

A 57 year old female was diagnosed with a lesion in the left lower lobe in a rheumatoid arthritis screening CT scan. Further workup for the active smoker included a PET-scan which confirmed a 21 × 26 × 16 mm (SUV max 3.0) well-circumscribed round lesion with some calcification, suggesting a hamartoma. The excision of the lesion was scheduled.

Material and Methods:

In diagnostic thoracoscopy we surprisingly found polypoid, well-vascularized pleural lesions localized on the diaphragm and basal parietal pleura, suggesting a localized pleural carcinomatosis. Biopsies were taken, wedge resection of the lesion in the left lower lobe and lymph node sampling was performed. Histology showed a sclerosing pneumocytoma mixed with a typical carcinoid, metastatic lymph node station 9 and pleural carcinomatosis. Due to the good outcome of typical carcinoids and limited local involvement of the pleura we performed a radical resection despite the presentation of a stage IV disease. The patient underwent extended lower lobectomy with radical lymphadenectomy, subtotal parietal pleurectomy, partial pericardiectomy and subtotal diaphragmatic resection. The pericardium was reconstructed with xenopericardial patch (Supple Peri-Guard® 14 × 8 cm), the diaphragm was reconstructed with a PTFE Membrane (Gore® Dualmesh®, 2 mm, 10 × 15 cm).

Results:

Histology showed a sclerosing pneumocytoma with infiltration of a typical carcinoid, TNM-classification (version 8 UICC) pT3 pN2a (2/26) pM1a (pleural) L1, V0, Ki-67< 2%, stage IV. Absence of necrosis, 1 mitosis per visual field (2 mm²). No expression of somatostatin receptors, synaptophysin, chromogranin-A, CD56, CD34 and CK7. In the 21 months follow up the patient is asymptomatic with no evidence of local relapse or metastasis in regular CT-scans.

Conclusion:

Sclerosing pneumocytoma is a rare tumor of the lung and surgical resection is curative. 4 cases of sclerosing pneumocytoma mixed with a non-metastasized carcinoid tumor, first described by Kim et al. 2013, have been reported. According to the literature this is the first case of a sclerosing pneumocytoma hosting a nodal and pleural metastasized typical carcinoid. Despite the locally advanced disease the decision to perform a radical resection seems to be warranted. The patient is in remission after 21 months follow up.