P2325 - A Rare Case of Extramedullary Plasmacytoma of the Anal Canal in a Patient With Multiple Myeloma

Thabuna Sivaprakasam, MBBS, Deepan Panneerselvam, MBBS, Rohit Sharma, MD, Rikesh Makanji, MD, Seth Felder, MD, Melissa Alsina, MD, Aamir Dam, MD, Luis Pena, MD, Jason Klapman, MD, Mark Friedman, MD
H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL

Introduction: Extramedullary plasmacytosis occurs in 18%-20% of the multiple myeloma cases. But gastrointestinal involvement is very rare and usually occurs in the small intestine. We present a case of multiple myeloma with extramedullary disease (EMD) of the anal canal, which is only the second case to be reported till now.

Case Description/Methods: This is a 60-year-old patient with relapsed, refractory Stage IIIB multiple myeloma (MM). He underwent an autologous stem cell transplantation, multiple courses of chemotherapy and radiotherapy for EMD of the iliac crest. He presented with one month of rectal pain and burning sensation with defecation. Physical examination showed an ulcerative mass on the left side of the anal verge. A colonoscopy was performed and showed a malignant ulcerated mass sized 3 x 4 cm on the left peri-anal area arising from below the dentate line. Pathology revealed sheets of necrotic plasma cells with some showing prominent nucleoli, that were CD 138 + and Lambda-ISH +. His PET-CT showed increased metabolic activity in the anus. These findings were consistent with plasmacytoma of the anal canal. The patient was started on palliative radiotherapy to the anal canal with markedly reduced pain and discomfort after completing two fractions of the treatment. His plasmacytoma will be followed up through the course of his treatment and he is scheduled to proceed with CAR-T immunotherapy.

Discussion: Very few cases of anal canal plasmacytomas have been reported in the literature. Though this patient’s anal mass initially gave the impression of a squamous cell carcinoma, this final diagnosis emphasizes the fact that the differential diagnosis in a multiple myeloma patient should include extramedullary spread when evaluating symptoms even in uncommon sites. The diagnosis of gastrointestinal EMD is crucial as it is associated with rapid progression, possibly a poor prognosis (median survival of 7 months) and therefore warrants more aggressive treatment. Though treatment recommendations are in place (such as Bortezomib-based regimens followed by autologous transplantation), reporting of such rare cases with a limited prognosis will facilitate the development of definitive therapeutic approaches. Finally, it has been suggested that allogeneic transplantation and novel drugs maybe associated with a higher incidence of EMD. A wider reporting of EMD cases as this patient would be helpful to analyze the validity of this proposed relationship in detail.


Figure: A -PET/CT demonstrates increased metabolic activity in the anus. While physiologic activity is not uncommonly visualized in the anus, given the history of extramedullary plasmacytoma of the anal canal, this finding would be concerning for neoplasm.
B - Plasma cells demonstrate lambda light chain restriction by in situ hybridization (ISH).
C - Neoplastic infiltrate is diffusely positive for plasma cell marker CD138.
D - High power view of the lesion demonstrates a neoplastic infiltrate with plasmacytoid morphology.
E - Colonoscopy showing the malignant, ulcerated mass arising from the anal canal.


Disclosures:
Thabuna Sivaprakasam indicated no relevant financial relationships.
Deepan Panneerselvam indicated no relevant financial relationships.
Rohit Sharma indicated no relevant financial relationships.
Rikesh Makanji indicated no relevant financial relationships.
Seth Felder indicated no relevant financial relationships.
Melissa Alsina indicated no relevant financial relationships.
Aamir Dam indicated no relevant financial relationships.
Luis Pena indicated no relevant financial relationships.
Jason Klapman indicated no relevant financial relationships.
Mark Friedman indicated no relevant financial relationships.


Thabuna Sivaprakasam, MBBS, Deepan Panneerselvam, MBBS, Rohit Sharma, MD, Rikesh Makanji, MD, Seth Felder, MD, Melissa Alsina, MD, Aamir Dam, MD, Luis Pena, MD, Jason Klapman, MD, Mark Friedman, MD. P2325 - A Rare Case of Extramedullary Plasmacytoma of the Anal Canal in a Patient With Multiple Myeloma, ACG 2021 Annual Scientific Meeting Abstracts. Las Vegas, Nevada: American College of Gastroenterology.