Follicular Lymphoma

General: Follicular lymphoma is the second most common NHL after diffuse large B-cell lymphoma and comprises approximately 22% of lymphomas.1 It occurs in older adults with a median age of 59 years and female predominance.1 Most patients have disseminated disease at presentation, with only 33% of patients having stage 1 or 2 disease. Bone marrow is involved in 40% of patients. This lymphoma generally has a long relapsing and remitting disease course with

Figure 52.5 Follicular lymphoma demonstrating a nodular architecture. The inset shows the cytologic features with predominantly small cleaved cells in this case

a 5 year overall survival of 72% but a failure-free survival of only 40%.1

Pathology: The hallmark of follicular lymphoma is the follicular architecture. The follicles are occupied by neoplastic cells recapitulating the normal lymphoid follicle. The lymphoma cells are neoplastic centrocytes (cleaved cells) and centroblasts (large noncleaved cells) in varying proportions, which determines the cytologic grade (Figure 52.5). Lymphoma cells are also seen between the neoplastic follicles when these areas are closely inspected and can also be a useful diagnostic feature. Cytologic grades are determined according to Mann and Berard (Table 52.2).12

The WHO classification suggests that overall and failure-free survival does correlate with cytologic grade, although conflicting data exists.1314 Evolution of treatment regimens will likely impact the importance of grading.

Diffuse areas can be seen in follicular lymphoma in varying proportions. The WHO recommends reporting the proportion of diffuse areas (see Table 52.1). The amount of diffuse component may indicate a worse prognosis, particularly with grade 3 lymphoma,15 and any diffuse component of sheets of large cells is best considered diffuse large B-cell lymphoma. A diffuse

Table 52.2

Cytologic grading of follicular lymphoma

Grade

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