Intratubal Pseudopapillary Histiocytic Hyperplasia: A New Histologic Variant in the Spectrum of Histiocytic Lesions...

Although histiocytic lesions of the fallopian tube are relatively rare compared to their epithelial counterparts, there exists a spectrum of histiocytic lesions involving the fallopian tube that are described under different terminologies dependent on the involved compartment of the fallopian tube. A common histologic denominator of all the hitherto reported tubal histiocytic lesions is the presence of sheets and clusters of histiocytes without any supportive connective tissue. The current study describes three cases of a heretofore-undescribed papillary histiocytic lesion in the lumen of the fallopian tube. All 3 lesions were characterized by avascular, hyaline collagenous papillary cores surrounded by a monotonous population of epithelioid cells, morphologically resembling mesothelial cell hyperplasia, but displaying a histiocytic immunophenotype with diffuse immunopositivity for CD68. Since the papillary cores did not harbor any vasculature, the term intratubal pseudopapillary histiocytic hyperplasia was proposed for this histiocytic proliferation which expands the spectrum of histiocytic lesions of the fallopian tube. Although probably of no clinical significance, practicing pathologists should be aware of this peculiar histiocytic lesion of the fallopian tube to avoid misdiagnosis and unnecessary immunohistochemical testing.