In situ follicular neoplasia: a clinicopathologic spectrum

AIMS

In situ follicular neoplasia (ISFN) occurs in ≈2-3% of reactive lymph nodes and is currently set apart from "partial involvement by follicular lymphoma" (PFL). ISFN can progress to overt lymphoma, but precise parameters to assess this risk and its association with related diseases remain incompletely understood. This study proposes to explore these parameters.

METHODS AND RESULTS

We reviewed 11 cases of ISFN and 1 of PFL between 2003 and 2018. Ten patients had ISFN in lymph nodes, one in the spleen. H&E and immunohistochemical stains were reviewed. Involvement of follicles by ISFN was scored using a 3-tier scheme. Of 5 cases with low ISFN scores, one had chronic myelomonocytic leukemia, one mycosis fungoides and three were free of hematopoietic diseases. Among them, 4 are alive and one was lost to follow-up. Of the 6 ISFN cases with high scores, 2 had concurrent marginal zone lymphomas, 1 concurrent diffuse large B-cell lymphoma (DLBCL), 1 Castleman-like disease, another progressive transformation of germinal centers with IgG4-related disease, and 1 no hematopoietic disease; all are alive except one who died of concurrent DLBCL. The patient with PFL developed DLBCL 7 years after diagnosis.

CONCLUSIONS

Based on this limited series, we conclude that only cases with high scores are associated with an overt lymphoma or an abnormal lymphoid process, and that scoring may be a useful parameter to assess risk for associated lymphoma, deserving further study. We also carried out a comprehensive review of the literature.

Concurrent chronic lymphocytic leukemia/small lymphocytic lymphoma and hairy cell leukemia: clinical, pathologic and molecular features

Simultaneous occurrence of hairy cell leukemia (HCL) and chronic lymphocytic leukemia/small lymphocytic lymphoma (termed CLL) is very rare. Clinical characteristics, pathology and management of these cases have not been well described. We present six patients with CLL and HCL or HCL variant (HCL-v). Of six patients, three were initially diagnosed with CLL and later developed concurrent HCL. Two patients had concurrent HCL or HCL-v and CLL at initial diagnosis. One had HCL first, followed by concurrent CLL. Polymerase chain reaction analysis demonstrated B-cell clonality in all cases, with two distinct clonal populations in four cases, and three clonal populations in one case. Five patients were treated with a combination of a purine analog such as fludarabine, cladribine, and pentostastin with either rituximab or ibrutinib, while one received dabrefenib and trametinib. All patients achieved a durable response to either CLL or HCL-directed therapy with reduction or ablation of coexisting B-cell clones.

The broad landscape of follicular lymphoma: Part II

Follicular lymphoma is a neoplasm derived from follicle center B cells, typically both centrocytes and centroblasts, in variable proportions according to the lymphoma grading. The pattern of growth may be entirely follicular, follicular and diffuse and rarely completely diffuse. It represents the second most common non-Hodgkin lymphoma, after diffuse large B-cell lymphoma and it is the most common low-grade mature B-cell lymphoma in Western countries. In the majority of cases, follicular lymphoma is a nodal tumor, occurring in adults and is frequently associated with the translocation t(14;18)(q32;q21)/IGH-BCL2. However, in recent years the spectrum of follicular lymphoma has expanded and small subsets of follicular lymphoma, which differ from common follicular lymphoma, have been identified and included in the current 2017 WHO classification. The aim of our review is to describe the broad spectrum of follicular lymphoma, pointing out that the identification of distinct clinicopathological variants of follicular lymphoma is relevant for the patient outcomes and treatment.

Primary Cutaneous Composite Lymphomas

Composite lymphomas have been defined as 2 distinct subtypes of lymphoma occurring at a single anatomic site. Composite lymphomas limited to the skin are a rare occurrence and pose a unique challenge. Many reported cases within the skin are combined B-cell and T-cell lymphomas, typically mycosis fungoides and a low-grade B-cell lymphoma. These cases are challenging to recognize because lymphoid infiltrates within the skin often include a mixed population of B cells and T cells. In particular, reactive lymphoid proliferations (pseudolymphomas), primary cutaneous low-grade B-cell lymphomas, and primary cutaneous CD4+ T-cell lymphoproliferative disorder may show nearly equal numbers of B cells and T cells. In order to exclude these possibilities, overwhelming evidence in support of each lymphoma is helpful, including abnormal architecture, cytology, and immunophenotype, as well as molecular genetic evidence of clonality.