massive localized lymphedema

The etiology of MLL is not entirely clear, but lymphatic obstruction associated with morbid obesity (body mass index greater than 40 kg/m2) likely plays a role.

MLL presents as a progressively enlarging mass with overlying indurated peau d’orange skin, most commonly involving the thigh.

Histopathologically, there is papillomatosis and hyperkeratosis overlying alternating edema and fibrosis of the dermis, expansion of the fibrous septa of mature subcutaneous fat, dilated lymphatics and small vessels surrounded by a lymphoid infiltrate, and hyperchromatic and mildly pleomorphic spindle cells.

A subset of MLL cases show dystrophic calcifications that mimic atypical fibroblast nuclei; the former may be highlighted with von Kossa stain to avoid misdiagnosis of ALT/WDLS.

Differential diagnosis

 Atypical lipomatous tumor/well-differentiated liposarcoma
-* ALT/WDLS typically arises in deep soft tissues and consists of atypical fibroblasts, lipoblasts, and atypical adipocytes, which helps differentiate it from MLL.

 Lipoma
-* Lipomas present as asymptomatic, well-circumscribed soft tissue tumors that are composed of mature lipocytes within a thin capsule;

 Angiosarcoma

• Angiosarcomas may arise in the setting of lymphedematous extremities, and MLL is thought to be a risk factor for the development of angiosarcoma.
• Histopathology of an angiosarcoma shows atypical endothelial cells lining crack-like vascular spaces.
• Stains should be positive for CD31, CD34, ERG, and D2-40. MYC is amplified in post-radiation angiosarcoma.

 Post-traumatic pseudolipoma

• Post-traumatic pseudolipoma, also known as nodular-cystic fat necrosis or encapsulated fat necrosis, occurs after local trauma and consists of necrotic adipocytes often surrounded by a fibrous capsule.

Case records

 http://www.asdp.org/education/case-study-of-the-month/public-case-study/?caseID=73

References

 Kurt H, Arnold C, Payne J, et al. Massive Localized Lymphedema: a clinicopathologic study of 46 patients with an enrichment for multiplicity. Mod Path 2016;29:75-82.

- Chopra K, Tadisina K, Brewer M, et al. Massive Localized Lymphedema Revisited: A Quickly Rising Complication of the Obesity Epidemic. Ann Plast Surg 2015;126-32.
Wang N, Walters R, Warren S. Massive Localized Lymphedema: A Soft Tissue Process that May Present to Dermatopathologists. Am J Dermatopathol 2010;32:380-83.

 Shon W, Ida C, Boland-Froemming J, Rose P, Folpe A. Cutaneous angiosarcoma arising in massive localized lymphedema of the mordbidly obese: a report of five cases and review of the literature. J Cutan Pathol 2011;38:560-564.

 Paola Dal Cin. Soft tissue tumors: an overview. Atlas of Genetics and Cytogenetics in Oncology and Haematology. July 2013. Available at http://atlasgeneticsoncology.org/Tumors/softissuTumID5042.html. Accessed February 10, 2017.