The histopathology of congenital hemangioma and its clinical correlations: a long-term follow-up study of 55 cases.

AIM: Congenital hemangiomas (CHs) can be subdivided into rapidly involuting, noninvoluting, and partially involuting subtypes (RICHs, NICHs and PICHs, respectively). During the first few days of life, RICHs may be associated with transient but sometimes marked thrombocytopenia. Given the rarity of CHs, the subtypes' histologic aspects and clinicopathological correlations have not been extensively characterized. METHODS AND RESULTS: We assessed the histopathological features of 10 RICHs, 25 NICHs and 20 PICHs, described the patients' long-term clinical outcomes, and assessed clinicopathological correlations. All CHs were located in the dermis and hypodermis, and comprised both capillary lobules (with three distinct histopathological patterns) and extralobular large vessels. Most of the extralobular vessels were abnormal veins and abnormal lymphatic vessels. We did not observe significant correlations between the CH subtype, the histopathological pattern, and the time of the histopathological assessment. Interestingly, unexpected intralobular expression of podoplanin was evidenced in neonatal biopsies of five RICHs and PICHs. Four of these five patients had concomitant thrombocytopenia. The podoplanin staining intensity decreased over time as the thrombopenia resolved and the tumor shrank. CONCLUSION: Histopathological features were similar in all three subtypes of CH, and were related to the time since disease onset; we consider that RICH, PICH and NICH form a single entity and differ only in their involuting potential. Along with the transient expression of intralobular podoplanin observed in some newborns' specimens, the lobular architecture might lead to misdiagnosis of tufted hemangioma or Kaposiform hemangioendothelioma.