October 2020 — Gastroenterology

The correct answer is Lymphangioma.

This lesion consists of variably sized vascular spaces lined by a single layer of endothelial cells which form anastamosing spaces occupied by eosinophilic proteinaceous debris, lymphocytes, and erythrocytes. Also present is an interstitial stroma with fibrosis and lymphoid infiltrate. Rare blood vessels are identified throughout the lesion. The endothelial lining is highlighted by vascular/lymphocytic markers and are HMB45, MelanA, and PAX-8 negative (not shown). These morphologic and immunophenotypic features are consistent with a lymphangioma. A hemangioma would likely contain more abundant smaller vascular spaces; they are also generally better circumscribed. While morphologically consistent with a lymphangiomyoma or angiomyolipoma, these lesions are generally both HMB45 positive.

Lymphangiomas often occur in young children, and the exact pathogenesis is not yet fully determined. They are traditionally classified into four separate categories (capillary, cavernous, cystic, and mixed). Frequently found in more superficial locations, they do rarely occur within the GI tract, most commonly within the small intestine, large intestine, and esophagus. A lymphangioma arising from the pancreas, such as with this lesion, is extremely rare.

References
1. Wiegand, S., Eivazi, B., Barth, P.J., Von Rautenfeld, D.B., Folz, B.J., Mandic, R., Werner, J.A., 2008. Pathogenesis of lymphangiomas. Virchows Archiv.. doi:10.1007/s00428-008-0611-z
2. Karajgikar, J., Deshmukh, S., 2019. Pancreatic Lymphangioma. Journal of Computer Assisted Tomography.. doi:10.1097/rct.0000000000000818
3. Fujii, M., Saito, H., Yoshioka, M., Shiode, J., 2018. Rare Case of Pancreatic Cystic Lymphangioma. Internal Medicine.. doi:10.2169/internalmedicine.9445-17
4. WHO Classification of Tumours of the Digestive System. International Agency for Research on Cancer, 2019.