Lobular capillary hemangioma
(Ref. Pathology of the skin, PH McKee, 3rd Ed. Elsevier-Mosby)
Lobular capillary hemangioma (pyogenic granuloma) is a very common benign vascular lesion that was for many years regarded as a reactive or infective process. This assumption was based on the extensive secondary changes that are almost invariably present in these lesions. However, the underlying process is that of a lobular proliferation of capillaries, which is much more likely to be neoplastic, and therefore it bas been redesignated lobular capillary hemangioma. It may arise at any age in either sex and shows a predilection for the head and neck (especially the mucous membranes) and limbs (particularly the arms and hand). Typically the lesion evolves rapidly, reaching its maximum size (usually less than 2 cm in diameter) within a matter of months. It presents as a pedunculated red or bluish nodule, which is prone to ulceration or bleeding. Complete spontaneous regression does not occur and rare patients present with multiple lesions. Congenital lesions are exceptional. Lobular capillary hemangioma may occur within a port wine stain and more rarely in association with unilateral dermatomal superficial telangiectasia. Multiple pyogenic granuloma-like lesions have been documented in association with capecitabine, topical tretinoin and isotretinoin therapy.
Local recurrence after excision is relatively frequent and in a small proportion of cases there is a recurrence with multiple satellite lesions that may be clinically worrying.This latter phenomenon tends to occur in younger individuals who very often have primary lesions on the trunk.
- Granuloma gravidarum is a variant that presents on the gingivae of pregnant women and involutes after delivery. Pregnancy may also induce lesions elsewhere.
- Subcutaneous or deep dermal pyogenic granuloma has a predilection for the upper limb. Since it never becomes ulcerated it is not associated with secondary inflammatory changes.
- Intravenous pyogenic granuloma is uncommon, but tends to occur on the neck and upper extremity of young adults.
Pyogenic granuloma consists of a usually exophytic, lobated, dermal mass made up of numerous small capillaries, often radiating from larger, more central vessels set in a loose edematous collagenous matrix. Endothelial cells have variably bland to plump nuclei and may be focally epithelioid, especially in mucosal tumors. Mitoses are commonly present and may be numerous. Focal cytological atypia as a result of degeneration may be seen.
Superficial infiltration by acute and chronic inflammatory cells in large numbers is a common finding, but this is seen only in ulcerated lesions. In such instances, the adjacent epidermis is often acanthotic and tends to form a well-defined collarette. When inflammation is marked, the overall features show a close resemblance to granulation tissue, except for the presence of capillary lobules in the deeper dermis at the base of the lesion.
Those cases developing satellite lesions often show extension into the subcutaneous fat.
Intravenous pyogenic granuloma is histologically similar to the more conventional lesion except that it lacks a significant inflammatory component.
The most important differential diagnosis is bacillary angiomatosis, an infectious vascular proliferation caused by a rickettsial organism Bartonella henselae. The latter occurs mainly in patients with AIDS and rarely in other immunosuppressed hosts or exceptionally in normal individuals. Although both lesions are architecturally very similar, bacillary angiomatosis is composed of pale eosinophilic endothelial cells and shows polymorphs throughout the lesion, accentuated in the vicinity of basophilic granular aggregates. The latter when stained with Giemsa or Warthin‑Starry show clumps of short bacilli.
Pyogenic granuloma may sometimes need to be distinguished clinically from other types of capillary hemangioma. Mucosal lesions with very plump endothelial cells and a high mitotic rate may be readily distinguished from angiosarcoma by their lobular architecture.