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Case 72 - Discussion

Hematopathology Case

 

 

CD20

CD20

CD79a CD3
CD21 CD21
BCL6 BCL6
CD10 CD10
BCL2 Ki67

 

Other negative stains:

CD4

CD8

CD5

CD15

CD30

CD21

ALK

 
 
  • Diagnosis: Primary Cutaneous Follicle Center Lymphoma (PCFCL).

  • Microscopic description: The large and symmetrical cutaneous lesion has a "stuck-on" appearance and is localized with only focal deeper invasion into the mid dermis. There is no epidermotropism of the tumor cells. The tumor demonstrates mixed growth patterns with mostly diffuse growth and focal nodular growth. The  neoplastic cells are large and highly pleomorphic with irregular, folded or multilobated nuclei. One or more small nucleoli are present with occasional prominent nucleoli. The tumor cells are mostly embedded in an expended follicular dendritic cells meshwork that is highlighted by CD21 immunostain. The tumor cells are positive for B-cell markers (CD20 and CD79a) and germinal center B-cell markers (CD10 and BCL6), but are negative for BCL2 and CD5. There is no reaction in the tumor cells for T-cell markers (CD3, CD4 and CD8). Other negative stains include CD15, CD30 and ALK.

  • Differential Diagnosis:

    • ALCL: more pleomorphic with hallmark cells. T cell origin. Primary cutaneous ALCL usually CD30+ and ALK-.

    • DLBCL or DLBCL transformed from conventional follicular lymphoma: more aggressive. This case has a very "benign" architecture. The CD10+/BCL6+ DLBCL is GCB type and is usually also BCL2 positive.

    • Primary cutaneous DLBCL, leg type: 90% involving leg, lack of CD21+ FDC meshwork in tumor cell, mostly BCL2+, BCL6+/-, CD10-.

    • Lymphomatoid papulosis: self-healing, CD4 T-cell origin, highly pleomorphic cells in an inflammatory background, CD30+ in type B.

  • Personal Notes:

    • Need to differentiate the PCFCL from conventional DLBCL or DLBCL transformed from FL. The clinical management can be very different. PCFCL usually only requires local treatment.

    • Should we grade primary cutaneous FCL as we usually do for the nodal FL? I feel it is probably unnecessary. According to the WHO book, the prognosis is almost the same regardless of the growth patterns, number of blasts, solitary or multiple skin lesions.

    • Still need to rule out systemic disease.

 

 

Primary Cutaneous Follicle Center Lymphoma

The Key Features

  • Medium to large centrocytes in follicular and/or diffuse growth patterns, no epidermal involvement.

  • BCL6+, CD10+, BCL2-, no BCL2 rearrangement.

  • Excellent prognosis, rarely extracutaneous involvement.

CLINICAL FEATURES

  • Germinal center B-cell origin.

  • Most common primary cutaneous B-cell lymphoma, 60% of all cases.

  • Mean age 51 years, M:F=1.5:1.

  • Characteristically as solitary or localized skin lesions of the scalp, forehead and trunk.

  • Usually localized to the skin, only ~10% disseminate to extracutaneous sites.

GROSS FINDINGS

  • Firm erythematous to violaceous plaques, nodules of variable sizes.

  • The surface is smooth and rarely ulcerated.

MICROSCOPIC FINDINGS

  • Perivascular and periadnexal, follicular and/or diffuse growth patterns.

  • Almost always sparing the epidermis.

  • Predominantly medium to large centrocytes and variable centroblasts.

  • The advanced tumors may show monotonous large centrocytes and multilobated cells and rarely spindle cells.

DIFFERENTIAL DIAGNOSES

  • ALCL: more pleomorphic with hallmark cells. T cell origin. Primary cutaneous ALCL usually CD30+ and ALK-.

  • DLBCL or DLBCL transformed from conventional follicular lymphoma: more aggressive. This case has a very "benign" architecture. The CD10+/BCL6+ DLBCL is GCB type and is usually also BCL2 positive.

  • Primary cutaneous DLBCL, leg type: 90% involving leg, lack of CD21+ FDC meshwork in tumor cell, mostly BCL2+, BCL6+/-, CD10-.

  • Lymphomatoid papulosis: self-healing, CD4 T-cell origin, highly pleomorphic cells in an inflammatory background, CD30+ in type B.

IMMUNOHISTOCHEMISTRY AND SPECIAL STAINS

  • CD20+, CD79a+

  • BCL6 constantly positive, CD10 positive in follicular growth pattern and negative in diffuse pattern.

  • BCL2 mostly negative.

CYTOGENETIC STUDIES

  • No BCL2 rearrangement in most cases.

TREATMENT AND PROGNOSIS

  • Excellent prognosis, 5-year survival ~95%, regardless of growth patterns, number of blasts, t(14;18) status and localized or multifocal lesions.

REFERENCES

  • Swerdlow, S.H., Campo, E., Harris, N.L., Jaffe, E.S., Pileri, S.A., Stein, H., Thiele, J., Vardiman, J.W. WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues, Fourth Edition. 2008.

  • Rein Willemze, Elaine S. Jaffe, Guš nter Burg, Lorenzo Cerroni, Emilio Berti, Steven H. Swerdlow, Elisabeth Ralfkiaer, Sergio Chimenti, JoseŽ L. Diaz-Perez, Lyn M. Duncan, Florent Grange, Nancy Lee Harris, Werner Kempf, Helmut Kerl, Michael Kurrer, Robert Knobler, Nicola Pimpinelli, Christian Sander, Marco Santucci, Wolfram Sterry, Maarten H. Vermeer, Janine Wechsler, Sean Whittaker, and Chris J. L. M. Meijer. WHO-EORTC classification for cutaneous lymphomas. Blood. 2005;105:3768-3785.