A 46-year-old woman underwent a laparotomy for an adnexal mass. At the time of surgery a nodular abnormality was noted in her spleen and a splenectomy was also performed. The adnexal mass was a benign ovarian cyst. The spleen contained a nodular grossly fibrotic mass measuring several cm in diameter. Sections from the splenic mass were sent for consultation. Representative microscopic images are seen below.
There are distinctly nodular proliferations of capillaries surrounded by variable concentric fibrosis. Entrapped blood vessels show perivascular hyalinized fibrosis. There is a scattered mixed inflammatory infiltrate consisting mainly of lymphocytes, plasma cells, and histiocytes within the fibrotic tissue and surrounding the vascular nodules.
What is your diagnosis?
This is an example of so-called sclerosing angiomatoid nodular transformation
(SANT) of the spleen. The angiomatous nodules are considered to represent altered, non-neoplastic red pulp entrapped by the surrounding fibrotic reaction. The cause of SANT is unclear, but similar nodular transformations have been noted in response to metastatic carcinomas.
At least some SANT have been considered to represent IgG4-related sclerosing lesions, though in the current case the total number of plasma cells was not overly high, and only a small number were of IgG4 type.
Most SANT are discovered as incidental findings, often in middle-aged women. No examples of this apparently reactive lesion have recurred or otherwise behaved in an aggressive fashion. SANT may be confused with other benign vascular lesions of the spleen including littoral cell hemangiomas and conventional hemangiomas. More importantly, it should not be mistaken for a borderline or overtly malignant vascular lesion such as "hemangioendothelioma," angiosarcoma, or Kaposi's sarcoma. The appearance of SANT is remarkably similar from case to case and awareness of this entity should avoid confusion.