Classification Systems for Kaposi Sarcoma
There is no officially accepted system for staging Kaposi sarcoma. Provided below, however, are several commonly used classification systems, [1] including those developed by the AIDS Clinical Trials Group (ACTG), [2] Mitsuyasu, [3] and the authors [4] (with subsequent modifications). The ACTG system uses three variables: tumor extent (T), immune status (I), and systemic symptoms (S). Each variable is classed as good risk (0) or poor risk (1).
The ATCG criteria had not previously been systematically assessed in sub-Saharan African patients. In a study of Ugandan adults with HIV-associated Kaposi sarcoma, Okuku et al reported that systemic symptoms were strongly associated with death in the early period after Kaposi sarcoma diagnosis, while tumor status was most predictive of death in the 4-24 month period. [5]
Those staging schemes may or may not correlate well with the presentation and outcomes in the many HIV-infected children in sub-Saharan Africa who have Kaposi sarcoma. [6] Pediatric Kaposi sarcoma has distinctive features compared with Kaposi sarcoma in adults. [7, 8] Lymph node involvement is more common in children, with marked immunosuppression linked with the highest mortality risk. Hence, a pediatric-specific staging classification has been proposed. [9]
Reduction of immunosuppression remains a cornerstone of therapy, particularly with post-transplant Kaposi sarcoma. [10]
In addition, detection of gastrointestinal Kaposi sarcoma is important for staging. Endoscopic biopsy utilizing hematoxylin and eosin staining, lymphatic and blood vessel endothelial cell markers, and human herpesvirus 8 (HHV-8) staining has demonstrated high diagnostic accuracy (> 0.80), with its accuracy increasing with endoscopic tumor staging. [11] Likewise, involvement of the ocular adnexa can be noteworthy. Ocular Kaposi sarcoma may be evident in the conjunctiva, eyelid, and/or cornea. [12]
Kim et al studied the expression of programmed death–1 (PD-1) and programmed death ligand 1 (PD-L1) in 50 cases of Kaposi sarcoma that had been histopathologically diagnosed and classified as early or late stage. With progression of disease, PD-1 expression fell while PD-L1 expression rose: In early-stage cases, PD-1 was expressed in 72.2% (13/18) and PD-L1 in 11.1% (2/18), while in late-stage cases, PD-1 was expressed in 43.8% and PD-L1 in 28.1%. [13]
T staging is being utilized, as noted below. [14]
Table. ACTG Classification System (Open Table in a new window)
Tumor (T) |
Extent of tumor |
T0 (good risk) |
Kaposi sarcoma is confined to skin and/or lymph nodes and/or demonstrates minimal oral disease (roof of mouth); the Kaposi sarcoma lesions in the mouth are flat rather than raised |
T1 (poor risk) |
Kaposi sarcoma lesions are widespread; one or more of the following is present:
|
Immune system (I) |
Status of the immune system, as measured by CD4 cell levels |
I0 (good risk) |
CD4 cell count is ≥200/µL (normal range, 600-1500/µL); more recent studies have used counts of either 150 or 100/µL |
I1 (poor risk) |
CD4 cell count is < 200/µL; more recent studies have used counts of either 150 or 100/µL |
Systemic illness (S) |
Extent of involvement within the body or systemic illness |
S0 (good risk) |
No systemic illness present; all of the following are true:
|
S1 (poor risk) |
Systemic illness present; one or more of the following is true:
|
Mitsuyasu classification system
Stage I:
-
Localized nodular Kaposi sarcoma in elderly men in North America and Europe
Stage II:
-
Localized, invasive, and aggressive Kaposi sarcoma (mostly seen in Africa)
Stage III:
-
Disseminated mucocutaneous Kaposi sarcoma in African children and men who have sex with men
Stage IV:
-
Stage III with visceral involvement
Classification system proposed and currently preferred by the author (including new recommended modifications)
Stage I:
-
Represents localized nodular Kaposi sarcoma, with >15 cutaneous lesions or involvement restricted to one bilateral anatomic site and few, if any, gut nodules
Stage II:
-
Includes both exophytic destructive lesions and locally infiltrative cutaneous lesions as locally aggressive Kaposi sarcoma
Stage III:
-
Generalized lymphadenopathic Kaposi sarcoma has widespread lymph node involvement, with or without skin lesions, but with no visceral involvement
Stage IV:
-
Disseminated visceral Kaposi sarcoma has widespread Kaposi sarcoma, usually progressing from stage II or stage III, with involvement of multiple visceral organs
Tables
Tumor (T) |
Extent of tumor |
T0 (good risk) |
Kaposi sarcoma is confined to skin and/or lymph nodes and/or demonstrates minimal oral disease (roof of mouth); the Kaposi sarcoma lesions in the mouth are flat rather than raised |
T1 (poor risk) |
Kaposi sarcoma lesions are widespread; one or more of the following is present:
|
Immune system (I) |
Status of the immune system, as measured by CD4 cell levels |
I0 (good risk) |
CD4 cell count is ≥200/µL (normal range, 600-1500/µL); more recent studies have used counts of either 150 or 100/µL |
I1 (poor risk) |
CD4 cell count is < 200/µL; more recent studies have used counts of either 150 or 100/µL |
Systemic illness (S) |
Extent of involvement within the body or systemic illness |
S0 (good risk) |
No systemic illness present; all of the following are true:
|
S1 (poor risk) |
Systemic illness present; one or more of the following is true:
|
