Massive localized lymphedema: additional locations and association with hypothyroidism.

We report the second series of a new entity called "massive localized lymphedema in morbidly obese patients" (MLL), recently described in medical literature. Our 6 cases present additional locations as well as an association with hypothyroidism. Huge masses, of longstanding duration ranging from 9 months to 8 years, afflicted the thigh, popliteal fossa, scrotum, suprapubic and inguinal region, and abdomen of morbidly obese adults. Although clinical impressions were generally of a benign process, including lipoma and recurrent cellulitis, the possibility of a malignant neoplasm could not be eliminated. Poorly defined and non-encapsulated, these skin and subcutaneous lesions were most remarkable for their sheer size, measuring 50.6 cm in mean diameter (range, 38-75 cm) and weighing a mean of 6764.5 g (range, 2,060-12,000 g) The overlying skin exhibited the induration and peau d'orange characteristic of chronic lymphedema. Grossly and histologically, a prominent marbled appearance, rendered by fibrous bands intersecting lobules of adipose tissue, simulated sclerosing well differentiated liposarcoma. However, the absence of atypical stromal cells, atypical adipocytes, and lipoblasts precluded the diagnosis of well differentiated liposarcoma. Instead, reactive features, encompassing lymphatic vascular ectasia, mononuclear cell infiltrates, fibrosis, and edema between the collagen fibers, as well as ischemic changes including infarction and fat necrosis, established the diagnosis of MLL. Although the pathogenesis of MLL may be as simple as obstruction of efferent lymphatic flow by a massive abdominal pannus and/or prior surgery, the presence of hypothyroidism in 2 of our patients suggests an alternative pathogenesis. Recognition of this entity by both clinicians and pathologists should avert a misdiagnosis as a low-grade liposarcoma.