Vasculitis in erythema induratum of Bazin: a histopathologic study of 101 biopsy specimens from 86 patients.

BACKGROUND Erythema induratum of Bazin is a mostly lobular panniculitis. There is considerable controversy in the literature about whether or not vasculitis is a histopathologic requirement to establish the diagnosis of erythema induratum of Bazin. Even accepting vasculitis as a histopathologic criterion, there is no agreement about the nature and size of the involved vessels. OBJECTIVE The main goal of our study was to investigate whether or not vasculitis was present in a large series of cases of erythema induratum of Bazin and, when vasculitis was found, to determine the nature and localization of the involved vessels. METHODS We studied 101 skin biopsy specimens from 86 patients with clinicopathologic diagnosis of erythema induratum of Bazin. Histopathologic criteria required in each case to be included in this study were: (1) a mostly lobular panniculitis with necrotic adipocytes at the center of the fat lobule; (2) inflammatory infiltrate within the fat lobule mostly composed of neutrophils in early lesions and granulomatous infiltrate in fully developed lesions; (3) significant fat necrosis; and (4) absence of other histopathologic findings that allow a specific diagnosis of other lobular panniculitis different from erythema induratum of Bazin. We also recorded the nature of the inflammatory cells involving the fat lobule, and the lesions were classified into two main categories: (1) early lesions, when the inflammatory infiltrate was mainly composed of neutrophils, with or without leukocytoclasis; and (2) fully developed lesions, when histiocytes and lipophages were the predominant inflammatory cells within the involved fat lobule. RESULTS Some type of vasculitis was evident in 91 cases (90.09%). A total of 47 biopsy specimens (46.5%) showed a mostly lobular panniculitis with necrotizing vasculitis involving the small vessels, probably venules, of the center of the fat lobule. Thirteen biopsy specimens (12.8%) showed a mostly lobular panniculitis with vasculitis involving both large septal veins and small vessels, probably venules, of the center of the fat lobule. Twelve biopsy specimens (11.8%) showed a mostly lobular panniculitis with vasculitis involving large septal veins, with no involvement or other septal or lobular vessels. Ten biopsy specimens (9.9%) showed a mostly lobular panniculitis with vasculitis involving large septal vessels, both arteries and veins, and necrotizing vasculitis involving the small vessels, probably venules, of the center of the fat lobule. Nine biopsy specimens (8.9%) showed a mostly lobular panniculitis with vasculitis involving large septal vessels, both arteries and veins, but with no involvement of the small blood vessels of the center of the fat lobule. Finally, 10 biopsy specimens (9.9%) showed a mostly lobular panniculitis without evidence of septal or lobular vasculitis in serial sections. Associated diseases included history of extracutaneous tuberculosis (including tuberculosis of the lung, lymph nodes, kidney, or bowel) in 12 cases (13.95%), previous episodes of superficial thrombophlebitis of the lower legs in 3 cases (3.72%), rheumatoid arthritis in one case (1.16%), Crohn disease in one case (1.16%), chronic lymphocytic leukemia in two cases (2.32%), hypothyroidism in two cases (2.32%), and positive serology for hepatitis B virus in 4 cases (4.65%) and for hepatitis C virus in 5 cases (5.81%). LIMITATIONS Serial sections were not performed in all cases. At least 10 sections were studied in each case. When vasculitis was evident in some of these first 10 sections, no further sections were cut, but when histopathologic features of vasculitis were not found in the first 10 sections, serial sections throughout the specimen were performed looking for vasculitis. Because some type of vasculitis was evident in the first 10 sections of 91 cases, serial sections were performed only in the remaining 10 cases and they failed to demonstrate clear-cut histopathologic features of vasculitis. On the other hand, this is a retrospective study that was performed from the histopathologic slides of our files, and only the clinical information contained in the report accompanying the biopsy specimen could be recorded. CONCLUSIONS In our experience, vasculitis is present in most lesions of erythema induratum of Bazin, and the nature, location, and size of the involved vessels is, from more to less frequent, as follows: (1) small venules of the fat lobule; (2) both veins of the connective tissue septa and venules of the fat lobule; (3) only veins of the connective tissue septa; (4) veins and arteries of the connective tissue septa and venules of the fat lobule; and (5) veins and arteries of the connective tissue septa. However, in some cases with all clinicopathologic features of erythema induratum of Bazin vasculitis could not be demonstrated with serial sections throughout the specimen and, therefore, the presence of vasculitis should be not considered as a criterion sine qua non for histopathologic diagnosis of erythema induratum of Bazin.