Skin nonmelanocytic tumor

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Contributed by Woo Cheal Cho, M.D.

• Primary cutaneous CD4+ small / medium T cell lymphoproliferative disorder:
  • Distinction from cutaneous lymphoid hyperplasia (particularly nodular T cell and mixed type) is challenging due to frequently overlapping histologic (i.e., dense lymphoid infiltrate composed of small to medium sized lymphocytes involving the dermis or subcutis), immunophenotypic (i.e., CD3+, CD4+, CD8-, CD30- phenotype) and clinical (i.e., solitary plaque or nodule on the head and neck region) features
  • Loss of 1 or more pan T cell markers (CD2, CD5 and CD7) more frequently seen in primary cutaneous CD4+ small / medium T cell lymphoproliferative disorder than in cutaneous lymphoid hyperplasia
  • Clonal T cell receptor gene rearrangements more commonly seen in primary cutaneous CD4+ small / medium T cell lymphoproliferative disorder than in cutaneous lymphoid hyperplasia
  • Presence of monoclonality, in the absence of identifiable triggering factors, favors primary cutaneous + small / medium T cell lymphoproliferative disorder over cutaneous lymphoid hyperplasia
• Primary cutaneous marginal zone B cell lymphoma:
  • Simulates Borrelia associated nodular B cell cutaneous lymphoid hyperplasia
  • Sheets of plasma cells and Dutcher bodies more frequently seen in primary cutaneous marginal zone B cell lymphoma than in cutaneous lymphoid hyperplasia
  • Neoplastic B cells express BCL2 while lacking immunoreactivity for CD5, CD10, BCL6 and cyclin D1
  • Neoplastic B cells may coexpress CD43
  • Monotypic plasma cells with light chain restriction (either kappa or lambda) more frequently seen in primary cutaneous marginal zone B cell lymphoma than in cutaneous lymphoid hyperplasia
  • Clonal immunoglobulin heavy chain gene rearrangements are more commonly seen in primary cutaneous marginal zone B cell lymphoma than in cutaneous lymphoid hyperplasia
• Mycosis fungoides:
  • Cutaneous lymphoid hyperplasia may histologically mimic mycosis fungoides, particularly if the infiltrate is T cell predominant and shows prominent lymphocytic exocytosis
  • Neoplastic cells of mycosis fungoides, however, typically exhibit cytologic atypia with hyperchromatic nuclei with irregular convoluted nuclear contours
  • Both mycosis fungoides and cutaneous lymphoid hyperplasia can show an increased CD4:CD8 ratio in the infiltrate
  • Presence of patches / plaques favors mycosis fungoides over cutaneous lymphoid hyperplasia
• Primary cutaneous follicular center lymphoma:
  • May simulate nodular B cell cutaneous lymphoid hyperplasia
  • Neoplastic follicles lack tingible body macrophages and have attenuated or absent mantle zones
  • Neoplastic B cells express BCL6, CD10 (variable; positive in follicular pattern but generally negative in diffuse pattern) while typically lacking immunoreactivity for BCL2

Which of the following features would most likely favor a diagnosis of cutaneous lymphoid hyperplasia over primary cutaneous CD4+ small / medium T cell lymphoproliferative disorder?

1. Dermal lymphoid infiltrate predominantly composed of small to medium sized pleomorphic T cells
2. Presence of B cells coexpressing CD43
3. Presence of T cell receptor beta (TCRB) and gamma (TCRG) gene rearrangements
4. Recent history of vaccination to the same site with an erythematous nodule
5. Presence of PD-1+ and CXCL13+ cells in the infiltrate

D. Recent history of vaccination to the same site with an erythematous nodule. Development of an erythematous nodule at the same site where vaccination was recently administered would favor a reactive process, such as cutaneous lymphoid hyperplasia (CLH). In the absence of identifiable triggering factors, however, distinguishing CLH from primary cutaneous CD4+ small / medium T cell lymphoproliferative disorder (CD4+ small / medium T cell lymphoproliferative disorder) is challenging on histologic grounds alone. Typically, the presence of clonality (choice C) detected by polymerase chain reaction would favor a diagnosis of primary cutaneous CD4+ small / medium T cell lymphoproliferative disorder over CLH, although clonality may also be seen in CLH occasionally. Histologic features of primary cutaneous CD4+ small / medium T cell lymphoproliferative disorder (choice A) are similar to those seen in CLH. Scattered to slightly increased follicular helper T cells (choice E) can be seen in both CLH and primary cutaneous CD4+ small / medium T cell lymphoproliferative disorder. The neoplastic B cells coexpressing CD43 (choice B) may be seen in primary cutaneous marginal zone B cell lymphoma, not in CLH or primary cutaneous CD4+ small / medium T cell lymphoproliferative disorder.

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Reference: Cutaneous lymphoid hyperplasia

Which of the following statements is true regarding cutaneous lymphoid hyperplasia?

1. Clonal T cell receptor beta (TCRB) and gamma (TCRG) gene rearrangements are never found in cutaneous lymphoid hyperplasia
2. Cutaneous lymphoid hyperplasia frequently progresses to a lymphoma
3. Diagnosis of cutaneous lymphoid hyperplasia requires clinical and pathologic correlation
4. Presence of monotypic plasma cells with kappa light chain restriction always favors a diagnosis of primary cutaneous marginal zone B cell lymphoma over cutaneous lymphoid hyperplasia
5. Triggering factors or etiologic agents are always identified in cutaneous lymphoid hyperplasia

C. Diagnosis of cutaneous lymphoid hyperplasia requires clinical and pathologic correlation. Accurate diagnosis of cutaneous lymphoid hyperplasia (CLH) requires clinical and pathologic correlation, including acquisition of appropriate clinical histories to determine the presence of a possible triggering factor. Albeit rare, monotypic plasma cells with a light chain restriction can also be seen in CLH (choice D). CLH is often idiopathic and definitive etiologic agents may not be found (choice E). Progression of CLH to a lymphoma is not a frequent finding (choice B). The presence of clonality in the infiltrate in the skin is not unique to malignancy (choice A) and can also be seen in various nonneoplastic conditions, including lichen sclerosus, lichen planus, pityriasis lichenoides chronica, pityriasis lichenoides et varioliformis acuta and CLH (J Invest Dermatol 2000;115:254, J Cutan Pathol 2002;29:447, Arch Dermatol Res 2000;292:568, Arch Dermatol 2001;137:305, Arch Dermatol 2000;136:1483).

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Reference: Cutaneous lymphoid hyperplasia