Residency Program - Case of the Month

Answer:

Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma)

Discussion:

MALT lymphoma is composed of heterogeneous small B-cells, comprises 7-8% of all B-cell lymphomas, has a male to female ratio of 1.2:1, and occurs at a mean age of 61. There is often a history of inflammation, as in the case of gastric MALT lymphoma where inflammation is caused by Helicobacter pylori. Autoimmune diseases, such as Hashimoto thyroiditis and Sjogren syndrome among others, have also been associated with MALT lymphomas. While the GI tract is the most common site of MALT lymphoma, especially the stomach, it is also seen in the salivary gland, lung, head and neck, ocular adnexa, skin, thyroid, and breast. MALT lymphoma involving the kidney has been previously reported but is extremely rare with less than 20 cases reported in the literature.

Although renal MALT does not appear to follow states of inflammation in previously reported cases, Garcia et al state that “MALT lymphomas share similarities with MALT lymphomas arising at other sites in that MALT lymphoma–associated translocations and NF-κBactivation occur in a subset of cases.”  Similarly, histologic and immunophenotypic features of MALT lymphomas include an invasive population of predominantly small lymphoid cells with mildly irregular nuclear contours and moderate cytoplasm with occasional plasmacytoid differentiation and an immunophenotypic signature that is positive for CD20 and negative for CD5, CD10, CD23, and cyclin D1.

Because MALT tumors of the kidney are often thought to be renal cell carcinoma on imaging, most patient have been treated with a radical nephrectomy. Most patients in the literature have not been followed long enough to determine the  success of such treatment treatment. Assuming renal MALT is not a separate entity, if it recurs it will generally be at other sites, which will develop like the other low grade lymphomas (Kato et al).

References:

1. Garcia M, Konoplev S, Morosan C, Abruzzo LV, Bueso-Ramos CE, Medeiros LJ. MALT lymphoma involving the kidney: a report of 10 cases and review of the literature. Am J Clin Pathol. 2007 Sep;128(3):464-73.
2. Kato, Y., Hasegawa, M., Numasato, S., Monma, N. and Fujioka, T. (2008), Primary mucosa-associated lymphoid tissue-type lymphoma arising in the kidney. International Journal of Urology, 15: 90–92. doi: 10.1111/j.1442-2042.2007.01923.x
3. Emre Tuzel, M.Ugur Mungan, Kutsal Yorukoglu, Alper Basakci, Ziya Kirkali, Primary renal lymphoma of mucosa-associated lymphoid tissue, Urology, Volume 61, Issue 2, February 2003, Page 463, ISSN 0090-4295, http://dx.doi.org/10.1016/S0090-4295(02)02267-7.

             (http://www.sciencedirect.com/science/article/pii/S0090429502022677)