title: Hobnail hemangioma: a pseudomalignant vascular lesion with a reappraisal of targetoid hemosiderotic hemangioma.
abstract: The clinicopathologic features of 15 cutanous hemangiomas having a distinctive and frequently pseudomalignant morphologic appearance are presented. There were 5 male and 9 female patients, whose ages at diagnosis ranged from 11 to 58 years (median 30.5). An angiomatous/pigmented, nontargetoid, flat, or exophytic lesion of variable duration was the main presenting sign. The tumor sizes ranged from 0.4 cm to 2 cm (median 1 cm). The locations included the lower limb, particularly the thigh (8); the trunk, including the shoulder area (4); the head (1); the gingiva (1); and the tongue (1). One patient had two lesions; none had a concomitant vascular anomaly or was suspected to have HIV infection. Treatment consisted of excisional biopsy in all cases. Follow-up information on 10 patients (range 4-66 months; median 13 months) showed no recurrence. On microscopic examination, the lesion showed a biphasic pattern characterized by the presence of well-formed, dilated, vascular channels in superficial dermis and a collagen-dissecting, pseudoangiosarcomatous pattern as the lesion infiltrated deeper into the dermis. The lining endothelium consistently showed distinctive hobnail cytomorphology; although there were endoluminal stromal papillae, there was no endothelial multilayering or tufting. Cytologic atypia was minimal or absent, and there were no mitoses. In 3 cases, the morphologic features were reminiscent of retiform hemangioendothelioma. Immunohistochemistry performed in 8 cases showed variable reactivity of endothelial cells with CD31, CD34, Factor VIII-related antigen, and Ulex europaeus agglutinin-1 in all cases; smooth muscle actin-positive pericytes were observed focally around some of the abnormal vascular spaces. The above-described hemangiomatous lesions share many features with so-called targetoid hemosiderotic hemangioma (a clinically descriptive term), but show a variable, often minimal, amount of hemosiderin deposition. The histologically descriptive term hobnail hemangioma is proposed to designate these lesions. Hobnail hemangioma should be distinguished from well-differentiated angiosarcoma, patch-stage Kaposi's sarcoma, and retiform hemangioendothelioma, with which it may be confused.
authors.affiliation: University Institute of Pathology, Lausanne, Switzerland.
authors.forename: L
authors.initials: L
authors.lastname: Guillou
authors.forename: E
authors.initials: E
authors.lastname: Calonje
authors.forename: P
authors.initials: P
authors.lastname: Speight
authors.forename: J
authors.initials: J
authors.lastname: Rosai
authors.forename: C D
authors.initials: CD
authors.lastname: Fletcher
mesh_terms: D000293:Adolescent; D000328:Adult; D014408:Biomarkers, Tumor / Q000378:metabolism; D002648:Child; D003937:Diagnosis, Differential; D005260:Female; D005887:Gingival Neoplasms / Q000378:metabolism / Q000473:pathology*; D018323:Hemangioendothelioma, Epithelioid / Q000378:metabolism / Q000473:pathology*; D006486:Hemosiderosis / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008875:Middle Aged; D012878:Skin Neoplasms / Q000378:metabolism / Q000473:pathology*; D014062:Tongue Neoplasms / Q000378:metabolism / Q000473:pathology*
chemical_list: D014408:Biomarkers, Tumor