Follicular colonization in melanocytic nevi and melanoma: A literature review

The lentiginous spread of melanocytes into the hair follicle can be observed in a number of benign melanocytic neoplasms such as in nevi but also in sun-induced melanocytic hyperplasia and melanoma. The follicular colonization by melanocytes in melanoma is classified into three distinct patterns: primary follicular melanoma, melanoma with folliculotropism, and invasive melanoma arising from melanoma in situ with folliculotropism. The role of follicular colonization in melanoma pathologic staging is still a matter of debate though the description of the latter has been recommended by the International Collaboration on Cancer Reporting. In this review, we will discuss the role of follicular colonization in melanoma and melanocytic nevi as well as the facts and controversies regarding this topic.

Adult Nodal Burkitt Lymphoma Forming Nodular Architectures

In this report, we discuss a case of nodal Burkitt lymphoma seen in a 60-year-old Japanese male patient. Microscopic features of the biopsied 30 mm-sized cervical lymph node revealed nodular architectures with starry sky appearance surrounded by small mantle zone B-lymphocytes. Immunohistochemical and molecular studies demonstrated typical features of sporadic Burkitt lymphoma: the atypical cells were positive for CD20, CD79a, CD10, CD23, HLA-DR, bcl-6, PAX5, c-myc, and cytoplasmic IgM, but negative for CD3, CD5, CD15, CD30, CD34, TdT, bcl-2, and MUM1. The mantle zone B-cells were clearly positive for bcl-2 and IgD. In situhybridization (ISH) analysis for immunoglobulin light chains showed kappa-type monoclonality. A few nuclei were labeled for Epstein-Barr virus-encoded small nuclear RNA (EBER). Ki-67 labeling index was nearly 100%. Within the nodule, CD21, CD23, and CD35-positive follicular dendritic cells were scattered with a small number of CD3/CD5-positive small T-lymphocytes, indicating that the nodular architecture represented follicular colonization of Burkitt lymphoma cells. Karyotypic analysis revealed t(8;14)(q24;q32), and IGH-MYC fluorescence in situ hybridization (FISH) demonstrated IGH-MYC fusion signals. The presentation of follicular colonization was quite unique in Burkitt lymphoma in the present case. Differential diagnosis is also discussed.

Expression of germinal center cell markers by extranodal marginal zone lymphomas of MALT type within colonized follicles, a diagnostic pitfall with follicular lymphoma

We reviewed 341 consecutive cases of marginal zone lymphoma (MZL) (47) or follicular lymphoma (FL) (294) of which 7 were difficult to distinguish due to perceived coexpression of BCL6 and BCL2 by tumor cells in follicular foci. This stimulated us to develop dual BCL6/BCL2 immunohistochemistry, allowing us to assess coexpression among individual cells. Dual staining confirmed coexpression in 6 of 7 cases, all extranodal MZL (ENMZL) based on overall features and representing 13% of MZL in this series. These findings confirm that MZL cells have plasticity regarding protein expression within the germinal center (GC) microenvironment, an important diagnostic pitfall. Intriguingly, in all MZL expressing BCL6, non-neoplastic GC B cells within colonized follicles showed diminished or absent CD10 expression but preserved BCL6 and high ki67. This finding suggests plasticity of CD10 expression in non-neoplastic GC B cells in the context of colonization by MZL, possibly related to NF-kB dysregulation.

Follicular lymphoma (in situ) pattern in the bone marrow: does it indicate an early stage in disease evolution?

Bone marrow involvement by an isolated interstitial lymphoid aggregate exhibiting the pattern and phenotype described for follicular lymphoma in situ (FLIS) has not been reported before. The detection of clinically silent FL in this case highlights the necessity of complete staging workup when such lesions are encountered in biopsies.

Richter syndrome with follicular colonization of chronic lymphocytic leukemia/small lymphocytic lymphoma cells mimicking follicular lymphoma

Follicular colonization is occasionally observed in marginal zone lymphoma. In rare cases, it has also been associated with mantle cell lymphoma. Chronic lymphocytic leukemia typically involves nodal or extranodal tissues as diffuse proliferation by complete effacement of the normal architecture. The involvement of chronic lymphocytic leukemia may be less frequently limited to the interfollicular areas. Here, we report a case of Richter syndrome of the small intestine that was initially diagnosed as follicular lymphoma of the gastrointestinal tract because of a partial follicular growth pattern in addition to a mainly diffuse proliferation pattern. The follicular pattern mimicking follicular lymphoma was shown to be composed of reactive follicles with follicular colonization of the original chronic lymphocytic leukemia cells. As the prognoses of Richter syndrome and follicular lymphoma of gastrointestinal tract are quite different, clinicians must carefully diagnose these conditions to avoid a misdiagnosis.