Primary cutaneous B‐cell lymphoma other than marginal zone: clinicopathologic analysis of 161 cases: Comparison with current classification and definition of prognostic markers

Abstract

Categorization of primary cutaneous B‐cell lymphomas (PCBCL) other than marginal zone (MZL) represents a diagnostic challenge with relevant prognostic implications. The 2008 WHO lymphoma classification recognizes only primary cutaneous follicular center cell lymphoma (PCFCCL) and primary cutaneous diffuse large B‐cell lymphoma, leg type (PCDLBCL‐LT), whereas the previous 2005 WHO/EORTC classification also included an intermediate form, namely PCDLBCL, other. We conducted a retrospective, multicentric, consensus‐based revision of the clinicopathologic characteristics of 161 cases of PCBCL other than MZL. Upon the histologic features that are listed in the WHO classification, 96 cases were classified as PCFCCL and 25 as PCDLBCL‐LT; 40 further cases did not fit in the former subgroups in terms of cytology and/or architecture, thus were classified as PCDLBCL, not otherwise specified (PCDLBCL‐NOS). We assigned all the cases a histogenetic profile, based on the immunohistochemical detection of CD10, BCL6, and MUM1, and a “double hit score” upon positivity for BCL2 and MYC. PCDLBCL‐NOS had a clinical presentation more similar to PCFCCL, whereas the histology was more consistent with the picture of a diffuse large B‐cell lymphoma, as predominantly composed of centroblasts but with intermixed a reactive infiltrate of small lymphocytes. Its behavior was intermediate between the other two forms, particularly when considering only cases with a “non‐germinal B‐cell” profile, whereas “germinal center” cases resembled PCFCCL. Our data confirmed the aggressive behavior of PCDLBC‐LT, which often coexpressed MYC and BCL2. The impact of single factors on 5‐year survival was documented, particularly histogenetic profile in PCDLBCL and BCL2 translocation in PCFCCL. Our study confirms that a further group—PCDLBCL‐NOS—exists, which can be recognized through a careful combination of histopathologic criteria coupled with adequate clinical information.

Primary cutaneous diffuse large B‐cell lymphoma, NOS and leg type: Clinical, morphologic and prognostic differences

“… as well as Lucioni et al. also found that PCLBCL/NOS patients were younger than PCLBCL/LT patients. In our series, women were significantly more commonly affected by PCLBCL/LT than men, whereas there was a male preponderance for PCLBCL/NOS.…”

Primary cutaneous large B‐cell lymphomas: relevance of the 2017 World Health Organization classification: clinicopathological and molecular analyses of 64 cases

“…Hans, and even more Hans modified, criteria have not played a role so far in the definition of PCLBCL categories, and have not been considered to be useful . We demonstrated that determining GC/NGC status by use of the Hans modified algorithm was a reliable diagnostic tool for PCLBCL diagnosis.…”

“…explained that categorisation of bcl‐2 negative patients as ‘PCLBCL, other’ was not justified, and proposed that this term should be used only for exceptional cases of PCBCL that do not fit the criteria for PCFCL or PCLBCL‐LT . In other series, including small‐cell and large‐cell PCBCLs, such ‘other’ cases represented 3.4–32.9% of cases . Discordance in the percentages highlights either the heterogeneity of this subgroup or the lack of reproducibility.…”

Multiple ulcerated nodules on the leg

“…The classification of PCDLBCL ‘other’ was used to describe all cutaneous cases of DLCBL that did not fit the criteria for follicle‐centre or leg type. However, the more recent WHO revision removed the nomenclature ‘other’ in favour of NOS . The pathogenesis of PCDLBCL‐NOS is unclear, but despite the limited number of case reports, it is thought to behave aggressively.…”