Clinically, disorders belonging to this category show a chronic long-standing course, no spontaneous regression in most cases, and no extracutaneous spread with involvement of visceral organs. In some cases, clonality of the infiltrate can be demonstrated. However, in most cases, the neoplastic cell clone never overcomes host control mechanisms and cannot expand and therefore never converts into clinically aggressive and spreading lymphoma. This category includes, for example: large plaque parapsoriasis, lymphomatoid clonal dermatitis, pagetoid reticulosis of Woringer-Kolopp type, syringolymphoid hyperplasia with alopecia, pre-Sezary syndrome, actinic reticuloid, and lymphomatoid papulosis.
Definite Malignant Lymphoma
This category includes CL that show a slowly progressive course with systemic spread in later stages and have the potential for transformation into more aggressive high-grade malignant lymphomas.
This category of CTCL include mycosis fungoides, Sezary syndrome, granulomatous slack skin, juvenile granulomatous CTCL, primary cutaneous CD30+ large-cell anaplastic T-cell lymphoma (which shows an excellent prognosis in contrast to its nodal counterpart) and most cases of CBCL. Survival is often not affected by the lymphoma or is greater than at least 5 years.
Some cases of CBCL which result from persistent antigen stimulation due to Borrelia infections may show complete regression after therapy with antibiotics, aphenomenon better establish in mucosa-associated lymphoid tissue (MALT) lymphomas. A majority of those cases might rather be considered as pseudolym-phomas, or may be very low-grade malignant CBCL from their very beginning. They have also been referred as semimalignant pseudolymphomas (1).
These diseases are characterized by a more rapid course than the low-grade lymphomas and usually show a fatal outcome after months or years. This category includes: subcutaneous panniculitis-like T-cell lymphoma, most lymphomas with cytotoxic phenotype and some cases of diffuse large B-cell lymphoma, and secondary or disseminated forms of pleomorphic lymphomas. These lymphomas usually exhibit a bad prognosis with survival times less than 2-5 years.
This model is not a new clinicopathologic classification, but represents a new approach for peripheral lymphoproliferative processes. The categorization respects the specific biologic behavior of the various disease entities. It does not contradict, but supplements existing classifications. It is provisional but flexible and can been modified as new knowledge is obtained.
When diagnosing a cutaneous lymphoproliferative process, we suggest identifying both the clinicopathologic entity as given in the classification systems and the biologic category. As an example, a lymphoproliferative process composed predominantly of centroblast and centrocyte-like B cells, confined to the skin would be diagnosed as a "primary cutaneous follicle center cell lymphoma'' and "primary cutaneous follicular lymphoma'' according to WHO and EORTC classification, respectively, and in addition, categorized as "definite low-grade malignant lymphoma" (see Table 2). This declaration includes the information that the lesion is
Table 2 Prognostic Categories of Primary Cutaneous Lymphomas (CL) and their Relationship to the WHO Classification (2001)
Prognostic categories of primary CL
Definite malignant lymphoma
WHO classification (truncated)
Mature T-cell and NK-cell neoplasms Mycosis fungoides
Primary cutaneous anaplastic large cell lymphoma Lymphomatois papulosis Subcutaneous panniculitis-like T-cell lymphoma
Peripheral T-cell lymphoma, unspecified
Adult T-cell leukemia/lymphoma Extranodal NK/T-cell, nasal type
Pagetoid reticulosis Syringolymphoid hyperplasia (or syringotropic MF)
Mycosis fungoides (MF)
Sezary syndrome (SS) Primary cutaneous anaplastic large cell lymphoma
Subcutaneous panniculitis-like T-cell lymphoma—indolent form
Pleomorphic small-cell lymphoma Granulomatous slack skin Juvenile granulomatous CTCL Cytotoxic TCL (CD8+)
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