RESUMO
Hydropic degeneration is a frequent degenerative change in otherwise typical uterine leiomyomas. Very rarely, however, a significant amount of edema fluid accumulates around the fascicles of neoplastic smooth muscle bundles and forms the characteristic multinodular growth pattern that is called perinodular hydropic degeneration of leiomyoma (PHDL). The gross findings, showing a vague worm-like appearance and very rarely having an extrauterine extension, and the microscopic features, showing perinodular retraction artifacts forming pseudovascular spaces, make it difficult to differentiate the tumor from intravenous leiomyomatosis or myxoid leiomyosarcoma. We described two cases of leiomyomas showing perinodular hydropic degeneration (PHD), a condition that has rarely been described in English literature, and discussed the mechanism of forming "extrauterine extension" or cotyledonoid features. One of our cases showed the typical features of cotyledonoid dissecting leiomyoma, the other showed those of intramural dissecting leiomyoma. An awareness of the gross and microscopic findings of PHDL is important not to overdiagnose a benign smooth muscle neoplasm as a more aggressive type of tumor. It is thought that intramural dissecting leiomyoma, cotyledonoid dissecting leiomyoma, and PHDL are not distinct, but closely related subtypes showing different phases of evolutionary changes.