Glomangioma of the lungs: a rare differential diagnosis of a pulmonary tumour.

Glomangiomas (glomus tumours) are uncommon, and in most cases are benign perivascular tumours, usually located in the dermis of the extremities, especially in the subungual region of the fingers. They also occur in other organs and in other regions of the body. Histogenetically, they are derived from modified smooth muscle cells of the glomus apparatus, which is associated with temperature regulation. These tumours are composed of capillaries, sometimes of dilated endothelial bigger vessels surrounded by nests of uniform, cytoplasm-rich cells with isomorphic round or ovoid nuclei (glomus cells). They also contain a variable amount of smooth muscle tissue. Three different types of glomus tumours are described according to their different components. The common form is predominantly made up of glomus cells, with a smaller amount of vessels and smooth muscle cells. The second variant, called ‘‘glomangioma’’, contains more partly dilated vessels resembling cavernous haemangiomas and is less circumscribed than the common form. In the most rare type, the ‘‘glomangiomyoma’’, the glomus cells undergo a transition to elongated smooth muscle cells. Immunohistochemically, glomus tumours usually show a positivity for vimentin and smooth muscle actin and a negativity for cytokeratin, neuroendocrine markers (chromogranin and others), CD31, CD34 and S100. These tumours are very rare in the lungs, and, to our knowledge, only 14 cases have been described, including two malignant glomus tumours.