What is the difference between Lymphomatoid Papulosus (LyP) and Primary Cutaneous Anaplastic Large Cell Lymphoma (pcALCL)?

It's a really matter of degree! Lyp, ALCL and nodal ALCL represent a disease spectrum. Lymphomatoid papulosus is a clone of activated T-cells presenting in the skin as a papule which may be ulcerated in the center. The histology of Lyp and ALCL is identical, with large cells and the expression of the activation marker, CD30. The major difference is that Lyp lesions are small, pink to red papules that come and go on their own (i.e., spontaneous regression is the key feature, although they may leave hyperpigmentation). There may be both T-cell receptor and immunoglobulin gene rearrangements present. There is an active immunity that causes spontaneous regression of the lesions. When a biopsy of Lyp comes back as large cell lymphoma, the patient may be over-treated with chemotherapy for lesions that will resolve on their own. Lyp lesions can be brought out by stress, viral infections, or in some cases, phototherapy. Lyp is associated with an increased incidence of ALCL, mycosis fungoides, and also Hodgkin's disease, but many patients never develop another lymphoma. 

ALCL lesions are by definition tumors (i.e., nodules larger than 1 cm that remain for long periods of time unless they are treated and they are often excised initially or treated with local radiation). They are commonly found on the extremities but may occur anywhere. The diagnosis of ALCL may be made on a lesion that would have regressed and would be otherwise classified as Lyp. Lyp is often responsive to topical therapies. ALCL may also regress spontaneously over time. Lyp lesions are often frequently seen in patients who also have either ALCL or patches and plaques of mycosis fungoides. In the latter case, Lyp may be over-interpreted as large cell transformation of mycosis fungoides although they usually regress or respond to therapy. It is not possible to cure Lyp with chemotherapy as the lesions recur. ALCL is also a chronic and indolent lymphoma that can be treated with local radiation or excision. 

We have seen several male patients who have developed extensive ALCL of the lower legs. This condition represents a very difficult treatment dilemma because chemo or radiation, if successful, may result in chronic leg ulcers and secondary infection leading to sepsis. Radiation of a limb may produce full thickness fibrosis in which more tumors may emerge. Click here to view figure of an elderly patient who developed recurrent tumors following treatment with CHOP which did not help. He then had local XRT leaving a large non-healing leg ulcer with new tumors forming above. He was not a good candidate for more chemotherapy with the opened leg ulcer. However, he is being treated with a monoclonal antibody to CD30 at a dose of 4 mg/kg and is doing well without symptoms. After two weeks, his lesions are beginning to flatten and his ulcer is showing signs of healing.

Madeleine Duvic, M.D.
Professor & Deputy Chairman, Dept of Dermatology
University of Texas, MD Anderson Cancer Center
Box 434; 1515 Holcombe Blvd.,
Houston, Texas 77030
Telephone: (713) 745-1113
Fax: (713) 745-3597
Contact: Donna Shotwell at (713) 745-4615