“In situ-like” mantle cell lymphoma: a report of two cases: Figure 1

Abstract

Mantle cell lymphoma (MCL) is a B cell neoplasm that most often shows a diffuse growth pattern. Two cases of MCL are reported here, both with a previous diagnosis of lymphoid hyperplasia. Morphologically, germinal centres are hyperplasic with a normal or discretely enlarged mantle zone, where foci of irregularly shaped small lymphocytes are seen. These are positive for CD20, CD5 and cyclin D1, confirming a diagnosis of in situ-like MCL. This type differs from the mantle zone pattern in that the neoplastic mantle zone is very thin and there is very little or no spread of tumour cells into interfollicular areas. To the best of our knowledge, this is the first report on such a pattern of MCL, which is important to recognise, as it can be confused with lymphoid hyperplasia.

Intrafollicular neoplasia/“in situ” lymphoma: A proposal for morphology and immunodiagnostic classification

“…Cases of ''in situ'' MCL are anedoctal [26,27] with some difficulties in distinguishing between MCL with a nodular pattern and real ''in situ'' MCL [26]. Although the problem of ''in situ'' lesions for MCL is increasingly recognized in the routine clinical practice, no clear guidelines for diagnosis of these patients have been defined so far.…”

The 2008 WHO classification of lymphoid neoplasms and beyond: evolving concepts and practical applications

“…79 Early involvement of lymph nodes by cells carrying the t(11;14) translocation and overexpressing cyclin D1 have been reported in several individual cases. 69,71,73,74,76 The cyclin D1-expressing cells are predominantly found in the inner area of the mantle zone of the follicles, but usually the rest of the mantle and the follicle have a For personal use only. on May 10, 2018. by guest www.bloodjournal.org From reactive appearance.…”

“…These have been designated as in situ FL or in situ MCL, referring to the fact that the clonal population is restricted in its distribution to its normal anatomic location, the germinal center or mantle zone, respectively (Table 3; Figure 2). [69][70][71][72][73][74][75][76] These lesions should be distinguished from partial involvement of the lymph node by overt lymphomas. Cases of in situ FL, or intrafollicular neoplasia, as alternatively termed in the WHO classification, represent expansions of CD10 and BCL2-positive lymphoid cells carrying the t(14;18) translocation found in germinal centers of an otherwise reactive lymph node.…”

Mantle cell lymphoma

“…Occasionally, the small lymphomatous elements can be almost exclusively restricted to the inner mantle zones or to narrow mantles, a pattern termed in situ MCL and thought to have a more indolent behavior. 15 Finally, the marginal zone-like subtype displays prominent foci of cells with abundant pale cytoplasm resembling marginal zone or monocytoid Belements. 7,12 Notably, these cases are at times characterized by splenomegaly, intrasinusoidal bone-marrow infiltration and a leukemic picture in the absence of lymph node involvement.…”