Kaposi sarcoma pathological features

1. Dr Syeda Madiha
13/01/2024
Histopathological findings in the
diagnosis of the stages of kaposi
sarcoma; which are more
valuable?
Seda Gun, Deniz Baycelebi, Ozlem Terzi and Levent Yıldız.
Journal of Histology & Histopathology
Volume 8 | Article 4
October 2021

2. Introduction
• The human herpesvirus 8 (HHV-8) virus, a member of the gamma-herpesvirus
subfamily, plays an important role in the pathogenesis of Kaposi sarcoma (KS),
a type of tumor.
• The Hungarian dermatologist, Moritz Kaposi, first described it as an “idiopathic
multiple pigmented sarcoma of the skin” in 1872.
• KS is a locally aggressive tumor with a low malignancy potential and is
characterized by patch, plaque and nodular stages in its natural development.
• Different histopathological features are prominent in each of the stages; hence,
the stages present different difficulties in the histopathological diagnosis and the
differential diagnosis.

3. • These difficulties in the differential diagnosis include benign or reactive
lesions in the patch stage, or other vascular sarcomas or cutaneous spindle
cell tumors in the nodule stage.
• Therefore, it is important to define valid and reliable histopathological
diagnostic features for each stage of KS.
• The histopathological features used in the diagnosis of KS were evaluated in
this case series. The study aimed to determine the finding or a group of
findings which is prominent in each stage of KS and which can effectively
identify a specific stage of KS.

4. Methods
• The histopathological details of 121 diagnosed Kaposi sarcoma cases were
studied retrospectively and reevaluated.

5. • The histopathological sections were evaluated independently by pathologists
according to the presence, absence and frequency of the following features:
• Stage
• Hyperkeratosis
• Acanthosis
• Ulceration
• Presence of spindle cells
• Fascicle formation
• Cleft-like space
• Horizontally oriented vascular bundles
• Large vessels in the periphery
• “Promontory” sign.
• Nodule formation
• Hyaline globules
• Extravasated erythrocytes
• Hemosiderin-laden macrophages
• Nuclear atypia
• Mitotic activity/10 high-power fields
• Necrosis and inflammatory cells and their type
(lymphocyte, plasma cell or neutrophil).

6. • In the evaluation of the data, minimum, median and maximum values were
used for qualitative evaluations, and figures and percentages (%) were used
for quantitative evaluations.
• For comparative analyses, the Pearson Chi-square test and multivariate
regression analysis were used. A statistical significance was considered to be
p<0.05.

7. Results
• In the present study, the median age of the 121 cases at the time of diagnosis
was 68.14 years (range: 26-93 years).
• KS was more common in males (62%) and most commonly present on the
feet (53%).

10. Hyperkeratosis

11. Ulceration

12. Spindle cells, fascicles

13. Horizontally orientated vascular bundles

14. Promontory sign

15. Nodular development

16. Hyaline globules, extravased erythrocytes

17. Hemosiderin-laden macrophages

18. Nuclear atypia, Mitotic activity

19. Necrosis

20. Inflammatory infiltration
(presence of lymphocytes, plasma cells and neutrophils)

25. Discussion
• Kaposi sarcoma, which originates from endothelial cells, is a multicentric
angioproliferative spindle cell tumor with histopathological and clinical
heterogeneity
• It is encountered as multiple lesions in the lower extremity in men in their
6th-7th decades.
• Previous studies have reported a nodular stage incidence of 36-87.5% . In
this study, the nodular stage (67,8 %) was the most commonly encountered.

26. • Alternatively, some studies have reported the plaque stage to be the most
commonly observed stage in HIV Positive KS Patients.
• Although not specific, hyaline globules, which are repositories for
erythrocytic degradation products, are argued to have diagnostic significance
in Kaposi sarcoma.
• In this study, erythrocyte extravasation was the most commonly encountered
histological feature (98.3%), and hyaline globules were observed in the
cellular cytoplasm or extracellular matrix in 95% of cases.

27. • There were significant differences in the incidences of hyperkeratosis,
acanthosis, ulceration, spindle cell presence, fascicles, cleft-like space,
horizontally oriented vascular bundles, hemosiderin, large vessels at the
periphery of the tumor, nodule, globule, atypia, mitosis and necrosis among
the stages.
• The initial or patch stage of KS is characterized by small, thin-walled,
bulging, endothelium-lined vessels surrounded by large ectatic vessels and
skin appendices.
• The opening of the small vascular structures to the lumens of the more ec-
tatic neoplastic channels is called the ‘promontory sign’ and is a
characteristic of KS.

28. • Mild inflammation characterized by plasma cells and lymphocytes,
extravasated erythrocytes and hemosiderin-laden macrophages can be
observed around the lesion.
• In the patch stage, the papillary dermis is generally intact.
• In this study, horizontally oriented vascular bundles, erythrocyte
extravasation and inflammation were the most common histological findings
in this stage. In contrast, necrosis was not observed.

29. • Among all the features used to confidently identify the plaque stage, the presence
of the promontory sign, erythrocyte extravasation, hemosiderin accumulation and
inflammation have been indicated as helpful findings in the literature.
• The study suggests that horizontal placement of vascular structures, erythrocyte
extravasation and the promontory findings are frequently observed and statistically
significant in the patch stage, and that searching for their comorbidity may help
support the diagnosis of that stage.
• In the plaque stage, the proliferating vascular structures infiltrate the dermis and
sometimes penetrate the subcutis.

30. • Spindle cells begin to concentrate and form bundles around the
proliferating vascular channels.
• In this study, the promontory sign, hyaline globules and hemosiderin were
the most frequently observed features in the plaque stage. Necrosis was not
observed.
• The promontory sign, which is a characteristic of the patch stage, was most
frequently detected in the plaque stage.
• When compared to the patch stage, the most significant histomorphological
finding was found to be the presence of hemosiderin in the plaque stage.”

31. • In the classical nodular stage of KS, intersecting, bundled spindle cells and
erythrocyte-containing clefts that separate vascular structures are observed.
• In the periphery of the nodular lesion, inflammatory cells (lymphocytes and
plasma cells), hemosiderin accumulations and dilated vessels are observed.
• Another characteristic, but non-specific, feature of this stage’s lesions is
hyaline globules.

32. • Dilated vascular spaces similar to a cavernous hemangioma may be
observed around some lesions.
• The large cutaneous nodules can ulcerate, and the tumor may exhibit cellular
pleomorphism, necrosis and mitotic figures in this stage.
• In this study, inflammation, globules, erythrocyte extravasation and spindle
cells were the most common histological findings in cases diagnosed in the
nodular stage.

33. • Compared to the plaque stage, the most valuable differentiating feature in
the nodular stage was the presence of mitosis.
• According to this study, it is believed that the combined detection of
ulceration, necrosis, atypia and mitosis is useful in distinguishing the
nodular stage from the other stages.

34. Conclusion
• The concomitance of hemosiderin, the horizontal placement of vascular
structures, erythrocyte extravasation and the promontory findings in the
patch stage; of promontory, globule and hemosiderin in the plaque stage;
and of an ulcer, necrosis, atypia and mitosis in the nodular stage are the most
effective histopathological parameters.
• In this retrospective study of KS, the demographic details and the
distribution of histopathological features by stage were similar to those
documented in the literature.

35. • The diagnosis of KS (which has different histopathological features at
different stages) can be more definitively made when the histopathological
finding that is most prominent at a given stage and best describes that stage
is evaluated.

36. Abstract
• Kaposi sarcoma (KS) is a local aggressive angioproliferative tumor with
various stages having different histopathological findings. Histopathological
findings have a diagnostic value depending on at what stage, how often, and
with what findings they are observed.
• The study aimed to determine the finding or a group of findings which is
prominent in different stages of KS and which can effectively identify that
stage.
• KS cases diagnosed were retrospectively reviewed. The relationship between
morphological parameters and disease stages was investigated. In comparative
analysis, Chi Square test and multivariate regression analysis were used.
Statistical significance level was accepted as p <0.05.

37. • When different stage groups and the frequency of parameters were
compared, there was statistical significance; the multivariate regression
analysis revealed that the presence of hemosiderin in the plaque stage was
OR: 25.7 (p: 0.02; CI 95%: 1.6-398.2) times higher than that of patch stage,
and the presence of mitosis in the nodule stage was OR: 3,7 (p: 0,002; CI
95%:3,8 - 489,7) higher than that of plaque stage. It was statistically
significant.
• The diagnosis of KS will be safer if evaluated with the most valid and best-
defining histopathological findings of the related stage.

38. Thank You