Anaplastic lymphoma kinase positive inflammatory myofibroblastic tumor of the urachus: A rare neoplasm in an unusual location

Abstract

Inflammatory myofibroblastic tumors (IMTs) are uncommon benign neoplasms in the abdomen, and urachal involvement is very rare. IMT of the urachus is usually mistaken clinically and radiologically for a malignant tumor. The tumor has spindle cell proliferation with a prominent inflammatory infiltrate and myxoid degeneration favoring other designations such as inflammatory pseudotumor and fibromyxoid pseudotumor. Complete excision is the treatment of choice. The case documented here was in a 50-year-old male, with an abdominal mass diagnosed on computed tomography scan as adenocarcinoma of urachus infiltrating the bladder. Histopathology showed a benign spindle cell tumor invading bladder muscle. Immunohistochemistry aided in diagnosing an anaplastic lymphoma kinase (ALK)-1 positive IMT. Approximately, 50% of the IMTs show ALK positivity, and though when present, it indicates neoplastic nature of the spindle cells, the pathogenesis of IMT is still elusive. The urachal IMTs need documentation in literature for their rarity and diagnostic dilemma posed by them.

Keywords

• Anaplastic lymphoma kinase-1 positivity
• inflammatory myofibroblastic tumor
• urachus