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🌱 created from: mycosis_fungoides

differential_diagnosis_of_mf

Other causes of erythroderma — Erythroderma is a less common cutaneous presentation of MF and is seen most commonly in patients with generalized atopic dermatitis, contact dermatitis, drug eruptions, or erythrodermic psoriasis. It can also be seen in patients with the idiopathic hypereosinophilic syndrome, some of whom have abnormal T cell clones [94]. The approach to patients with generalized erythroderma is presented separately. (See “Erythroderma in adults”.)

Other causes of pruritus — Pruritus is a frequent manifestation of MF, although it is typically not present in the absence of cutaneous findings [95]. The erythrodermic form of MF and Sézary syndrome are extremely pruritic and there are case reports of pruritus preceding the onset of skin findings by several years [96]. Pruritus is a common symptom that occurs in a diverse range of skin diseases and may appear as a prominent feature of extracutaneous disorders such as systemic, neurologic, and psychiatric diseases (table 2). The evaluation of the patient with pruritus is discussed separately. (See “Pruritus: Etiology and patient evaluation”.)

Sézary syndrome — As described above, patients with MF may have atypical lymphocytes with cerebriform nuclei (ie, Sézary cells) in their peripheral blood (picture 13). A diagnosis of Sézary syndrome is made when there is a particularly high number of these cells circulating in the peripheral blood in the presence of a cutaneous erythroderma occupying more than 80 percent of the body surface area. This is equivalent to the T4 and B2 designation in the TNMB classification system. The diagnosis of Sézary syndrome is presented in more detail separately. (See “Clinical presentation, pathologic features, and diagnosis of Sézary syndrome”.)

Adult T cell leukemia-lymphoma — Adult T cell leukemia-lymphoma (ATL) is a peripheral T cell lymphoma associated with infection by the human T-lymphotropic virus, type I (HTLV-I). Approximately 50 percent of patients with ATL will have skin lesions at diagnosis, often simulating those seen in MF. ATL, however, is much more likely to have disseminated extracutaneous disease with frequent lymphoma in the nodes, liver, bone, and central nervous system. A key differentiating feature is the presence of HTLV-I in the malignant cells of ATL, which can be determined by testing for the antibody in the blood. ATL is common in Japan and the Caribbean and is unusual in the mainland United States. (See “Clinical manifestations, pathologic features, and diagnosis of adult T cell leukemia-lymphoma”.)

Subcutaneous panniculitis-like T cell lymphoma — Subcutaneous panniculitis-like T cell lymphoma (SPTCL) is an uncommon peripheral T cell lymphoma that typically presents with one or more usually painless subcutaneous nodules or poorly circumscribed indurated plaques that may clinically resemble panniculitis. Similar to MF, SPTCL expresses CD3, does not express CD56 or demonstrate Epstein-Barr virus infection, and has clonally rearranged T cell receptor (TCR) genes. SPTCL differs from MF in that it is centered on the subcutaneous tissue rather than the dermis and epidermis, does not express CD4, and expresses CD8 and cytotoxic granule proteins (TIA-1, granzyme B, and/or perforin). Patients with symptoms and signs of hemophagocytic lymphohistiocytosis (HLH) often have a less favorable outcome [97]. (See “Clinical manifestations, pathologic features, and diagnosis of subcutaneous panniculitis-like T cell lymphoma”.)

Primary cutaneous anaplastic large cell lymphoma — Primary cutaneous anaplastic large cell lymphoma (PC-ALCL) is a peripheral T cell lymphoma characterized by the diffuse infiltration of the upper and deep dermis and the subcutaneous tissue by large lymphoid cells. Unlike MF, PC-ALCL expresses cytotoxic molecules (TIA-1, granzyme B, and/or perforin) and CD30. (See “Primary cutaneous anaplastic large cell lymphoma”.)

Cutaneous gamma/delta T cell lymphoma — Cutaneous gamma/delta T cell lymphoma (G/D TCL) is another cytotoxic T cell lymphoma that can present with HLH, thus it is important to consider evaluation for HLH whenever clinically indicated [98]. G/D TCL is usually an aggressive type of cutaneous T cell lymphoma [63,99]; however, a subset of patients can present indolently with patches and plaques that mimic clinical and pathologic features of MF. These patients can later develop the more typical features of the aggressive G/D TCL.

Cutaneous B cell lymphoma — The skin lesions of CTCL may not be easily distinguished clinically from those of B cell lymphomas. MF can be distinguished from cutaneous B cell lymphomas through their expression of T cell markers such as CD2, CD3, and CD5. In addition, MF can be identified by TCR gene rearrangement studies. The diagnosis of primary cutaneous B cell lymphomas is presented separately. (See “Primary cutaneous follicle center lymphoma” and “Primary cutaneous marginal zone lymphoma” and “Primary cutaneous diffuse large B cell lymphoma, leg type”.)