Inflammatory myofibroblastic tumour of the rectum with a novel ALK fusion diagnosed on cytology: not just another submucosal GIST!

Inflammatory Myofibroblastic Tumor of the Anus: A Case Report

Inflammatory myofibroblastic tumors (IMTs) are neoplastic lesions characterized by the proliferation of spindle cells with myofibroblastic features and lymphocyte infiltration. Primary lesions can develop in several locations but rarely arise in the colon as described herein. The present case was that of a 69-year-old woman who visited our hospital with complaints of bloody bowel discharge and a prolapsed mass from the anus. A 20-mm tumor was identified on visual and digital examination. Lower gastrointestinal endoscopy revealed a pedunculated, elevated lesion above the dentate line, which showed contrast enhancement on abdominal computed tomography. The patient was preoperatively diagnosed with an anal polyp, which was resected transanally. During the procedure, a mobile tumor coated by anal epithelium was observed at the 11 o'clock position above the dentate line. Deeper parts of the tumor were contiguous with the internal anal sphincter (IAS) muscle. Suspecting a neoplastic lesion, we resected the mass en bloc with part of the IAS. Tumor histopathology after surgery led to a final diagnosis of an IMT of the anus. IMT is difficult to diagnose preoperatively. No adjuvant therapy has been formally established; thus, an adequate surgical margin and close monitoring are essential.

ALK-positive Large B-Cell Lymphoma With Multiple Epithelial Antigen Expression and PABPC1::ALK Fusion: A Novel Molecular Alteration

Anaplastic lymphoma kinase (ALK)-positive large B-cell lymphoma (LBCL) is a very rare type of LBCL with an aggressive clinical course and poor prognosis. This diagnosis can be challenging given the varied morphology (immunoblastic, plasmablastic, or anaplastic), frequent lack of B-cell antigens, and especially in cases with expression of epithelial antigens. Here, we report a case of ALK-positive LBCL with unusual expression of 4 epithelial-associated markers (AE1/AE3, CK8/18, EMA, and GATA3) and novel poly(A) binding protein cytoplasmic 1 (PABPC1)::ALK fusion which has not been previously reported in this entity. This case also emphasizes the use of comprehensive immunophenotyping that includes multiple lineage-specific antibodies when faced with a malignancy without a clear differentiation to avoid misdiagnosis. This case only achieved partial response to combination chemotherapy, radiation, and ALK inhibitor regimens, and furthers our understanding of this uncommon lymphoma.