Diffuse meningotheliomatosis of the lung

Definition

In most cases, meningothelial lesions are single and constitute incidental curiosities. Rarely they are multiple involving one or multiple lobes. Diffuse meningotheliomatosis is a rare condition in which patients develop diffuse bilateral pulmonary meningothelial nodules. The immunoprofile of these lesions resembles that of meningiomas.

Epidemiology

This condition is extremely rare and has been reported in adults in the sixth to eight decade of life. There is a marked female predominance.

Clinical features

Patients present with dyspnea, fatigue, cough or spontaneous pneumothorax. They have mildly restrictive pulmonary function tests.

Radiology

There is reticulonodular infiltrates or ground glass opacities with nodules generally up to 3 mm diameter, sometimes up to 8 mm, raising the differential diagnoses of interstitial lung disease or disseminated malignancy. There is no lymphadenopathy.

Macroscopic appearances

The cut surface of the lung shows multiple small grey-white nodules, most common in the subpleural zone.

Histopathology

The nodules are predominantly perivenular, sometimes along alveolar septa or associated with ectatic vascular spaces. They vary from well demarcated to ill-defined. The constituent cells are oval or spindled with copious eosinophilic cytoplasm. There are uniform oval nuclei and some cells show pseudonuclear inclusions. The cells may have a whorled configuration. Vessels walls may be hyalinised. There is no necrosis or mitotic activity. Apart from the presence of haemosiderin-laden intra-alveolar macrophages, the adjacent lung parenchyma is unremarkable.

Immunohistochemistry

	Vimentin	positive1
	EMA	positive1
	AE1/AE3	negative1
	Cam5.2	negative1
	S-100	negative1
	HHF35	negative1
	SMA	negative1
	Chromogranin	negative1
	Synaptophysin	negative1
	CD34	negative1

Ultrastructure

Cells have complex interdigitating processes with frequent desmosomes. The cytoplasm contains abundant intermediate filaments. There is absence of basement membrane, neurosecretory granules, mucin or zymogen granules or microvilli.

Differential diagnosis

Neuroendocrine tumourlets: have a higher nuclear/cytoplasmic ration with stippled chromatin; they are positive for cytokeratin, chromogranin and synaptophysin.
Metastatic chemodectoma: the cells are large and pleomorphic. They are positive for chromogranin and synaptophysin.
Metastatic carcinoma with lymphatic dissemination; cells are pleomorphic and positive for cytokeratins.
Pulmonary meningioma; this is a solitary lesion

Management

Prognosis

Follow up is inadequate to assess the prognosis.

References

1 Suster S,Moran CA Diffuse pulmonary meningotheliomatosis. Am J Surg Pathol 2007; 31:624-31

This page last revised 29.4.2007.