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Splenic hamartoma and capillary hemangioma are distinct entities: Immunohistochemical analysis of CD8 expression by endothelial cells
Splenic Hamartoma and Capillary Hemangioma Are Distinct Entities: lmmunohistochemical by Endothelial Cells
Analysis of CD8 Expression
LAWRENCE R. ZUKERBERG, MD, BRUCE L. KAYNOR, BS, MARK L. SILVERMAN, MD, AND NANCY L. HARRIS, MD The histologic and immunohistologic features of two morphologically similar splenic tumors, a capillary hemangioma and a splenic hamartoma, are reported. The hemangioma was composed predominantly of small vascular channels lined by endothelium expressing factor VIII-related antigen and lacking T-subset antigen (CDS). In contrast, the splenic hamartoma was predominantly a spindle cell lesion with numerous vascular channels coursing through the tumor; these contained splenic-type endothelium expressing both CDS and factor VIII-related antigen. Our results justify the concept that the splenic hamartoma is a tumor of splenic origin or a true hamartoma and is distinct from the splenic capillary hemangioma. HUM PATHOI. 22:1258-1261. Copyright cc‘ 1991 by W.B. Saunders Company Primary nonlymphomatous tumors of the spleen are unusual. Most are splenic cysts or benign vascular tumors,’ mostly hemangiomas; cases of splenic hamartoma and angiosarcoma are encountered less commonly. I-” are of the cavernous type; Most splenic hemangiomas these are easily distinguished from splenic hamartomas by their gross and microscopic appearance. However, little information exists concerning small vessel hemangiomas and their relationship with splenic hamartomas. I which they may histologically resemble; some investigators have suggested that splenic hamartomas may be identical to capillary hemangiornas.‘,“.~,” Recently, splenic sinusoidal lining cells (splenic endothelium) have been shown to react with monoclonal antibodies to T-lymphocyte subsets as well as with the usual endothelial cell markers (such ;is factor VIII-related antigen).‘,* Specificall\:, the splenic cndothelium reacts with monoclonal antibodies to the T-subset antigen CD8 and, as reported by some, with CD3. but not with the pan T-cell antigens (1113 or (3.5. A vascular tumor of splenic origin. such as a splenic hamartoma. should contain splenic-type endothelium (CD8+, factor VIII+), in contrast to a tumor of vascular origin, which should contain vascular endotheliurn (GIN-, factor VIII+). We studied two splenic vascular tumors, a splenic hamartoma and a small vessel hemangioma, using
frozen tissue sections and antibodies against factor VIIIrelated antigen and CD8 in order to define the phenotype of the endothelial cells in these lesions and to determine their relationship to one another. METHODS Routine histologic sections were prepared from formalinfixed, paraffin-erribeclded tissue and were stained with hemzitoxylin-eosin. Immunoperoxidase stains were performed on frozen tissue sections as prc+ously described! with the avidin biotin complex technique (Vector Laboratories Inc, Burlingame, CA). Tissue sections were stained with antibodies to factor VIII-related antigen (DAKO. Carpinteria, CA). CD3 (Becton Dickinson, San Jose, CA). CD4 (Becton Dickinson). (:1X3 (
CASE REPORTS Case No. 1 (,'/i~lird Hitlory. A
70-year-old mzi with recently diagprostate carcinoma was found to have a splenic mass on abdominal computed tomography, which was done to evaldisease. The patient was otherwise healthy. with no history uttt’ disorders. He underwent explorator? of 11-;1u1na orhematologic and recovered uneventfully. I:iparotoniy arid splenectomy, ~wsctl
FIGURE 1. The splenic hemangioma has a central steltate white scarand does not bulge above the cut surface of the adjacent spleen.
1258
SPLENIC
FIGURE 2. Small vascular spaces and one larger vessel separated by fibroblasts and collagen give this capillary hemangioma a spindly appearance (top). (Hematoxylin-eosin stain: magnification . The negative for CD8 in contrast to the endothelium (right) spleen (bottom). (Immunoperoxidase
HAMARTOMA
(Zukerberg
et al)
.* I
f( br (11)X. Thr tndothclial cells in the ;rdj;c~(‘111norma splc~r~li
sp;lr5c. Vie diagnosis 0Pcapillarytype hemangioma was made. Iniiti~~noperosiclase stains on frozen tissue sections (Fig 2) revealed that the endothelial cells lining the ~~~scula~- thanIrcls tq)~~~sw~l f;ic.tor VIII-related antigen, but were negative
1259
HUMAN PATHOLOGY
Volume 22, No. 12 (December
1991)
revealed a well-circumscribed mass, 5 cm in diameter (Fig 3). The tumor was firm, brown-tan, and solid, with no areas of hemorrhage or necrosis. The tumor bulged above and focally compressed the adjacent unremarkable splenic parenchyma. Microscopic examination revealed a tumor composed of plump, bland spindle (stromal) cells with focal aggregates of small lymphocytes (Fig 4). Numerous small and medium-sized endothelial-lined spaces coursed through the tumor. Immunoperoxidase stains on frozen tissue sections (Fig 4) revealed that the vascular channels within the tumor stained for factor VIII-related antigen and that both the vascular endothelium and many small lymphocytes stained for CD8. With antibodies to CD3 and CD4 there was staining of numerous small lymphocytes (greater than with CD8), but no staining of the vascular channels or normal spleen. Immunostaining for type IV collagen showed abundant staining of the fibrous tissue and stromal cells between the vascular channels.
DISCUSSION We report the histologic and immunohistologic features of two morphologically similar splenic tumors: a small vessel hemangioma and a splenic hamartoma. Our results indicate that these tumors contain different types of endothelial cells, justifying the concept that they represent distinct entities. The small vessel hemangioma of the spleen is a vascular tumor similar to hemangiomas elsewhere in the body, with vascular endothelium expressing factor VIII-related antigen and lacking CDS. In contrast, the splenic hamartoma is a splenic neoplasm or true hamartoma, with splenic-type endothelium expressing both CD8 and factor VIII-related antigen. Both patients described in this report were asymptomatic, and their tumors were detected by radiologic examination for evaluation of unrelated problems. Most hemangiomas and hamartomas are discovered incidently at autopsy or at splenectomy for another reason.4 Occasional cases are symptomatic, producing hypersplenism or, less often, spontaneous rupture, hemolytic anemia, or massive splenomegaly. “‘-‘s The clinical symptoms and radiologic appearances of splenic hemangiomas and FIGURE 4. The splenic hamartoma is composed of bland spindle cells with admixed lymphocytes and small vascular channels (top). (Hematoxylin-eosin stain; magnification x200.) The vascular channels are CD8 (bottom) and factor VIII-related antigenpositive. (Immunoperoxidase stain; magnification x200.)
FIGURE 3. The splenic hamartoma has a homogeneous appearance and bulges above the cut surface of the adjacent spleen.
1260
hamartomas overlap and are not useful in distinguishing these lesions from each other or from other splenic tumors. Macroscopically, both tumors were well-circumscribed lesions without infiltrative borders. However, the gross appearance of these lesions differed and may be useful in differential diagnosis: the splenic hemangioma was a flat lesion with a white, stellate central scar, while the splenic hamartoma was dark brown, homogeneous, and bulged above the cut surface of the spleen. While previous reports”’ vary as to the color of splenic hamartomas, they are usually described as bulging above the cut surface of the spleen, in contrast to the flat cut surface of splenic hemangiomas.
SPLENIC
HAMARTOMA
Histologically, the two lesions were also sin&u, hut cac.11 had distinctive features. The hemangioma was c~omposecl predominantly of small vascular channels separated th a small amount of fibrous tissue and collagen, whereas the hamartoma was a predominantly spindle cell lesion composed mostly of stromA cells, with smaller number-s of vascular channels or sinuses coursing through the turrlor. Other features that help to separate these lesions include the presence of scattered larger vcssrls in Ihe hemangioma but not in the hamartoma, alld the presence of numerous lymphocytes in the hamartoma but not in the hemangioma. These latter features prohabl) reflect the fact that lymphocytes are a normal component of the spleen and large vessels are ;III integra.1 component of hemangiomas, and may he useful diagnostic criteria in borderline cases. The presence of numerous small lymphocytes expressing CD8 in the splenic hamartoma but not in the hemangio,ma (Figs 2 and 4) highlights the usefulness of this featme in distinguishing between these two lesions. Buckley and Dickson’ postulated that since splenic sinusoidal lining cells and certain T lymphocytes share nlembrane antigens. functional relationships may exist among th’ese c,ell types. Therefore, the finding of nunlerous T cells in a tumor derived from normal splenic elements, sucll as a splenic hamartoma, would be expected. Antibodies that detect T cells in paraffin sections are 11ow ;\vailable (CD45RO. CD43); such stains will highlight the presence of T cells and may be useful for distinguishing between hamartoma and hemangioma in questionable cases. This is the first study to report the immunohistochemical findings in splenic vascular tumors, using monoclonal antibodies to T-cell subsets on frozen sections. 0~ results are complementary to those of Falk and Stutte.’ ’ who used histochemistry and paraffin section imr~~l.~~~ohistt,chemist~ to demonstrate that the endothelium of a splenic hamartoma resembled normal
1261
(Zukerberg
et al)
Analysis of CD8 Expression
LAWRENCE R. ZUKERBERG, MD, BRUCE L. KAYNOR, BS, MARK L. SILVERMAN, MD, AND NANCY L. HARRIS, MD The histologic and immunohistologic features of two morphologically similar splenic tumors, a capillary hemangioma and a splenic hamartoma, are reported. The hemangioma was composed predominantly of small vascular channels lined by endothelium expressing factor VIII-related antigen and lacking T-subset antigen (CDS). In contrast, the splenic hamartoma was predominantly a spindle cell lesion with numerous vascular channels coursing through the tumor; these contained splenic-type endothelium expressing both CDS and factor VIII-related antigen. Our results justify the concept that the splenic hamartoma is a tumor of splenic origin or a true hamartoma and is distinct from the splenic capillary hemangioma. HUM PATHOI. 22:1258-1261. Copyright cc‘ 1991 by W.B. Saunders Company Primary nonlymphomatous tumors of the spleen are unusual. Most are splenic cysts or benign vascular tumors,’ mostly hemangiomas; cases of splenic hamartoma and angiosarcoma are encountered less commonly. I-” are of the cavernous type; Most splenic hemangiomas these are easily distinguished from splenic hamartomas by their gross and microscopic appearance. However, little information exists concerning small vessel hemangiomas and their relationship with splenic hamartomas. I which they may histologically resemble; some investigators have suggested that splenic hamartomas may be identical to capillary hemangiornas.‘,“.~,” Recently, splenic sinusoidal lining cells (splenic endothelium) have been shown to react with monoclonal antibodies to T-lymphocyte subsets as well as with the usual endothelial cell markers (such ;is factor VIII-related antigen).‘,* Specificall\:, the splenic cndothelium reacts with monoclonal antibodies to the T-subset antigen CD8 and, as reported by some, with CD3. but not with the pan T-cell antigens (1113 or (3.5. A vascular tumor of splenic origin. such as a splenic hamartoma. should contain splenic-type endothelium (CD8+, factor VIII+), in contrast to a tumor of vascular origin, which should contain vascular endotheliurn (GIN-, factor VIII+). We studied two splenic vascular tumors, a splenic hamartoma and a small vessel hemangioma, using
frozen tissue sections and antibodies against factor VIIIrelated antigen and CD8 in order to define the phenotype of the endothelial cells in these lesions and to determine their relationship to one another. METHODS Routine histologic sections were prepared from formalinfixed, paraffin-erribeclded tissue and were stained with hemzitoxylin-eosin. Immunoperoxidase stains were performed on frozen tissue sections as prc+ously described! with the avidin biotin complex technique (Vector Laboratories Inc, Burlingame, CA). Tissue sections were stained with antibodies to factor VIII-related antigen (DAKO. Carpinteria, CA). CD3 (Becton Dickinson, San Jose, CA). CD4 (Becton Dickinson). (:1X3 (
CASE REPORTS Case No. 1 (,'/i~lird Hitlory. A
70-year-old mzi with recently diagprostate carcinoma was found to have a splenic mass on abdominal computed tomography, which was done to evaldisease. The patient was otherwise healthy. with no history uttt’ disorders. He underwent explorator? of 11-;1u1na orhematologic and recovered uneventfully. I:iparotoniy arid splenectomy, ~wsctl
FIGURE 1. The splenic hemangioma has a central steltate white scarand does not bulge above the cut surface of the adjacent spleen.
1258
SPLENIC
FIGURE 2. Small vascular spaces and one larger vessel separated by fibroblasts and collagen give this capillary hemangioma a spindly appearance (top). (Hematoxylin-eosin stain: magnification . The negative for CD8 in contrast to the endothelium (right) spleen (bottom). (Immunoperoxidase
HAMARTOMA
(Zukerberg
et al)
.* I
f( br (11)X. Thr tndothclial cells in the ;rdj;c~(‘111norma splc~r~li
sp;lr5c. Vie diagnosis 0Pcapillarytype hemangioma was made. Iniiti~~noperosiclase stains on frozen tissue sections (Fig 2) revealed that the endothelial cells lining the ~~~scula~- thanIrcls tq)~~~sw~l f;ic.tor VIII-related antigen, but were negative
1259
HUMAN PATHOLOGY
Volume 22, No. 12 (December
1991)
revealed a well-circumscribed mass, 5 cm in diameter (Fig 3). The tumor was firm, brown-tan, and solid, with no areas of hemorrhage or necrosis. The tumor bulged above and focally compressed the adjacent unremarkable splenic parenchyma. Microscopic examination revealed a tumor composed of plump, bland spindle (stromal) cells with focal aggregates of small lymphocytes (Fig 4). Numerous small and medium-sized endothelial-lined spaces coursed through the tumor. Immunoperoxidase stains on frozen tissue sections (Fig 4) revealed that the vascular channels within the tumor stained for factor VIII-related antigen and that both the vascular endothelium and many small lymphocytes stained for CD8. With antibodies to CD3 and CD4 there was staining of numerous small lymphocytes (greater than with CD8), but no staining of the vascular channels or normal spleen. Immunostaining for type IV collagen showed abundant staining of the fibrous tissue and stromal cells between the vascular channels.
DISCUSSION We report the histologic and immunohistologic features of two morphologically similar splenic tumors: a small vessel hemangioma and a splenic hamartoma. Our results indicate that these tumors contain different types of endothelial cells, justifying the concept that they represent distinct entities. The small vessel hemangioma of the spleen is a vascular tumor similar to hemangiomas elsewhere in the body, with vascular endothelium expressing factor VIII-related antigen and lacking CDS. In contrast, the splenic hamartoma is a splenic neoplasm or true hamartoma, with splenic-type endothelium expressing both CD8 and factor VIII-related antigen. Both patients described in this report were asymptomatic, and their tumors were detected by radiologic examination for evaluation of unrelated problems. Most hemangiomas and hamartomas are discovered incidently at autopsy or at splenectomy for another reason.4 Occasional cases are symptomatic, producing hypersplenism or, less often, spontaneous rupture, hemolytic anemia, or massive splenomegaly. “‘-‘s The clinical symptoms and radiologic appearances of splenic hemangiomas and FIGURE 4. The splenic hamartoma is composed of bland spindle cells with admixed lymphocytes and small vascular channels (top). (Hematoxylin-eosin stain; magnification x200.) The vascular channels are CD8 (bottom) and factor VIII-related antigenpositive. (Immunoperoxidase stain; magnification x200.)
FIGURE 3. The splenic hamartoma has a homogeneous appearance and bulges above the cut surface of the adjacent spleen.
1260
hamartomas overlap and are not useful in distinguishing these lesions from each other or from other splenic tumors. Macroscopically, both tumors were well-circumscribed lesions without infiltrative borders. However, the gross appearance of these lesions differed and may be useful in differential diagnosis: the splenic hemangioma was a flat lesion with a white, stellate central scar, while the splenic hamartoma was dark brown, homogeneous, and bulged above the cut surface of the spleen. While previous reports”’ vary as to the color of splenic hamartomas, they are usually described as bulging above the cut surface of the spleen, in contrast to the flat cut surface of splenic hemangiomas.
SPLENIC
HAMARTOMA
Histologically, the two lesions were also sin&u, hut cac.11 had distinctive features. The hemangioma was c~omposecl predominantly of small vascular channels separated th a small amount of fibrous tissue and collagen, whereas the hamartoma was a predominantly spindle cell lesion composed mostly of stromA cells, with smaller number-s of vascular channels or sinuses coursing through the turrlor. Other features that help to separate these lesions include the presence of scattered larger vcssrls in Ihe hemangioma but not in the hamartoma, alld the presence of numerous lymphocytes in the hamartoma but not in the hemangioma. These latter features prohabl) reflect the fact that lymphocytes are a normal component of the spleen and large vessels are ;III integra.1 component of hemangiomas, and may he useful diagnostic criteria in borderline cases. The presence of numerous small lymphocytes expressing CD8 in the splenic hamartoma but not in the hemangio,ma (Figs 2 and 4) highlights the usefulness of this featme in distinguishing between these two lesions. Buckley and Dickson’ postulated that since splenic sinusoidal lining cells and certain T lymphocytes share nlembrane antigens. functional relationships may exist among th’ese c,ell types. Therefore, the finding of nunlerous T cells in a tumor derived from normal splenic elements, sucll as a splenic hamartoma, would be expected. Antibodies that detect T cells in paraffin sections are 11ow ;\vailable (CD45RO. CD43); such stains will highlight the presence of T cells and may be useful for distinguishing between hamartoma and hemangioma in questionable cases. This is the first study to report the immunohistochemical findings in splenic vascular tumors, using monoclonal antibodies to T-cell subsets on frozen sections. 0~ results are complementary to those of Falk and Stutte.’ ’ who used histochemistry and paraffin section imr~~l.~~~ohistt,chemist~ to demonstrate that the endothelium of a splenic hamartoma resembled normal
1261
(Zukerberg
et al)