Diagnosis
Malignant B cell characteristics
Normal B cells of a germinal center possess rearranged immunoglobulin heavy and light chain genes, and each isolated B cell possesses a unique IgH gene rearrangement. Since Burkitt lymphoma and other B-cell lymphomas are a clonal proliferative process, all tumor cells from one patient are supposed to possess identical IgH genes. When the DNA of tumor cells is analyzed using electrophoresis, a clonal band can be demonstrated, since identical IgH genes will move to the same position. On the contrary, when a normal or reactive lymph node is analyzed using the same technique, a smear rather than a distinct band will be seen. This technique is useful since sometimes benign reactive processes (e.g. infectious mononucleosis) and malignant lymphoma can be difficult to distinguish. Microscopy
The tumor consists of sheets of a monotonous (i.e., similar in size and morphology) population of medium-sized lymphoid cells with high proliferative and apoptotic activity. The "starry sky" appearance seen under low power is due to scattered tingible body-laden macrophages (macrophages containing dead apoptotic tumor cells). The old descriptive term of "small non-cleaved cell" is misleading. The tumor cells are mostly medium in size (i.e., tumor nuclei size similar to that of histiocytes or endothelial cells). "Small non-cleaved cells" are compared to "large non-cleaved cells" of normal germinal center lymphocytes. Tumor cells possess small amounts of basophilic cytoplasm with three to four small nucleoli. The cellular outline usually appears squared off.
These discolorations have led to the term "sun fungus". Pathophysiology
In cases of tinea versicolor caused by the fungus Malassezia furfur, lightening of the skin occurs due to the funguss production of azelaic acid, which has a slight bleaching effect. Diagnosis
Tinea versicolor may be diagnosed by a potassium hydroxide (KOH) preparation and lesions may fluoresce copper-orange when exposed to Woods lamp. The differential diagnosis for tinea versicolor infection includes:
Progressive macular hypomelanosis
Pityriasis alba
Pityriasis rosea
Seborrheic dermatitis
Erythrasma
Vitiligo
Leprosy
Syphilis
Post-inflammatory hypopigmentation

Treatment
Treatments for tinea versicolor include:

Topical antifungal medications containing selenium sulfide are often recommended. Ketoconazole (Nizoral ointment and shampoo) is another treatment. It is normally applied to dry skin and washed off after 10 minutes, repeated daily for two weeks. Ciclopirox (ciclopirox olamine) is an alternative treatment to ketoconazole, as it suppresses growth of the yeast Malassezia furfur. Initial results show similar efficacy to ketoconazole with a relative increase in subjective symptom relief due to its inherent anti-inflammatory properties. Other topical antifungal agents such as clotrimazole, miconazole, terbinafine, or zinc pyrithione can lessen symptoms in some patients. Additionally, hydrogen peroxide has been known to lessen symptoms and, on certain occasions, remove the problem, although permanent scarring has occurred with this treatment in some people. Clotrimazole is also used combined with selenium sulfide. Oral medications are viewed as a second-line of treatment for pityriasis versicolor in the event of widespread, severe, recalcitrant or recurrent cases.