Jennifer, 68, presents with a small itchy patch of scaly redness on the left lateral breast (pictured).
It has been present for years and she has intermittently used topical steroids prescribed by various doctors. It does tend to improve with this treatment, but never completely, and it recurs when the steroid is ceased.
Her medical history includes anxiety, chronic insomnia and osteoporosis for which she takes doxepin, lemborexant, periciazine and risedronate. None of these medications are new or coincide with development of the rash.
She has not changed any skincare or wash products and has no dermatological history of note.
Biopsy is performed which shows a moderate dermal infiltrate of lymphocytes, spongiosis and lymphocytic exocystosis into the epidermis. The lymphocytes are almost all T-cells, predominantly staining for CD3.
What is the most likely diagnosis?
Correct!
Mycosis fungoides is the most common type of cutaneous T-cell lymphoma. It is uncommon, but accounts for about 50% of primary cutaneous lymphomas.
Mycosis fungoides usually occurs in mid- to late-adulthood and is more common in males and Caucasian patients. It is generally an indolent disease with an estimated five-year survival of 87%. Patient age, skin stage, and presence of extracutaneous disease are the major predictors of survival.
Chronic itch is a common presenting feature, which may be evident before there are any other clinical signs of disease. Clinical signs, when they emerge, are usually very slowly progressive from patches to plaques, with potential eventual progression to form tumours. However, most patients are diagnosed early, prior to tumour formation.
Visible skin lesions usually begin as poorly defined erythematous, finely scaling patches in sun-protected areas, such as the lower trunk, breast and thighs.
Diagnosis can be difficult and may require multiple biopsies over time. Histopathology characteristically shows infiltrates of malignant T-lymphocytes.
Management options vary depending on patient preference and stage of disease. Options include a watch and wait approach, as individual lesions may spontaneously remit. Topical treatment options include steroids, chemotherapy and radiotherapy. Systemic therapy may involve oral retinoids, chemotherapy or immunotherapy.