Case: AP250
Contributor's Comment: Lymphangioleiomyomatosis (LAM) is a rare condition occurring in women of reproductive age characterized by a nodular, often widespread proliferation of myoid cells along lymphatic channels with involvement of lung and lymph nodes. Sites of affected lymph nodes include mediastinum, retroperitoneum, and pelvis, where enlarged masses forming lymphangiomas and lymphoangiomyomas may be seen. Occasionally uterine involvement is also present. LAM is usually sporadic but patients with tuberous sclerosis complex are often affected. The constituent cells are spindle and clear with epithelioid features. Immunoreactivity for desmin and actin, as well as HMB-45 is present. It must be distinguished from leiomyomatosis which express smooth muscle markers and not HMB-45. PEComa (Perivascular epithelioid cell tumors) is a subset of HMB-45 positive epithelioid mesenchymal tumors of the uterus with an uncertain relationship to pure smooth muscle tumors.
Folpe AL, Kwiatkowski DJ. Perivascular epitheliod cell neoplasms: pathology and pathogenesis. Human Pathol 2010, 41, 1-15.