Primary cutaneous follicle center lymphomas with high Ki-67 indices arising on the arm and leg

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Primary cutaneous follicle center lymphomas with high Ki-67 indices arising on the arm and leg
Dear Editor, Primary cutaneous follicle center lymphomas (PCFCL) generally present as solitary lesions, and approximately 15% of cases present as multifocal skin lesions. 1,2 PCFCL exhibit a predilection for the head (39.4%) and trunk (39.2%), but they can occur on the legs (6.4%) or arms (2.3%) in rare cases. 2 They exhibit a follicular, follicular and diffuse, or diffuse growth pattern. 1 PCFCL cells express CD20 and BCL6 in all cases 3 and generally do not express BCL2. 3,4 CD10 is detected in some cases with a follicular growth pattern, but it is generally absent from cases that display a diffuse growth pattern. 1 We describe a case of diffuse-type PCFCL, involving an unusual presentation. Multiple cutaneous and subcutaneous tumors arose on the patient's left arm and leg, which expressed BCL2 and CD10 (as is seen in nodal follicular lymphoma) 1 and had high Ki-67 indices.
An 80-year-old man presented with a red tumor on his left forearm, which had been present for 2 months (Fig. 1a). A skin biopsy demonstrated the diffuse infiltration of medium to largesized atypical lymphoid cells into the dermis (Fig. 1b,c). Mitoses were observed. Immunohistochemistry revealed that the tumor cells expressed CD20, BCL2, BCL6 and CD10. MUM1, Myc, cyclin D1, CD5, CD56, TdT and Epstein-Barr encoding region staining were negative ( Fig. 1d-j). The Ki-67 proliferative index was 60% (Fig. 1k). Clonally rearranged IGH genes were present but no BCL2 rearrangement was detected. Diffuse-type PCFCL was diagnosed. Subsequently, another tumor appeared on the left elbow (Fig. 1l), and the patient noticed two subcutaneous tumors on his left leg (Fig. 1m,n). The tumors on his arm started to ulcerate. Positron emission tomography revealed 18 F-fluorodeoxyglucose uptake by the four tumors, but no other organ involvement was detected. Radiotherapy was administrated and the four tumors were completely cured. No recurrence has been observed after 2.5 years.
We diagnosed the present case as PCFCL because the tumor was predominantly composed of medium to large-sized tumor cells with cleaved nuclei. These findings were inconsistent with diffuse large B-cell lymphoma, which is composed of diffuse homogenous infiltrates of large tumor cells with noncleaved, round nuclei. Moreover, the negative MUM-1 and Myc staining were suggestive of PCFCL.
Koletsa et al. 5 reported a case of diffuse-type PCFCL with a high Ki-67 index (90%), which presented as an ulcerated tumor on the arm and evolved rapidly over a 2-month period. They suggested that a subgroup of PCFCL that displays rapid clinical changes, diffuse infiltration and high Ki-67 indices exists, and that such tumors should be treated as high-grade lymphomas. Our case also suggests that a high Ki-67 index leads to rapid evolution and ulceration, which are indicative of aggressive local behavior.
Primary cutaneous follicle center lymphoma has an excellent prognosis, and BCL2 expression, the growth pattern and the presence of multifocal skin lesions are not associated with a worse prognosis. 1,2,4 Although the tumors in the present case