ANSWERS
The diagnosis is endometriosis of the FT, where the tubal mucosa shows complete replacement by endometrial glands and stroma [Figures 1a and b]; the latter is highlighted by CD 10 immunohistochemical stain [Figure 1c]. Apart from the uterine wall (adenomyosis), several extra-uterine sites can be involved, typically the ovary or peritoneum and also the gut or vaginal–rectal septum, explained on the basis of ‘retrograde menstruation’, celomic metaplasia, or differentiation of the embryonic cell rests.[1]
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Figure 1: (a) Tubal mucosa showing complete replacement by endometrial glands and stroma (HE, ×100). (b) Endometrial glands and stroma lining the tube (HE, ×400). (c) CD 10 immunohistochemical stain highlighting the endometrial stroma (×100)
There is a wide variation in the incidence of tubal endometriosis (6.9% to 69%).[2] Usually associated with lesions at other sites, it can also occur in isolation with a greater frequency of occurrence on the left side (as seen in the present case, 4.3 to 55% versus 1.6 to 31% on the right side).[2] Three histological patterns have been described.[3] Serosal or sub-serosal endometriotic lesions in the distal FT are seen with peritoneal involvement, while some lesions develop in the proximal tubal segment after tubal ligation or salpingectomy. The case presented depicts the intra-luminal type that was present in the ampullary region of the left FT. It is to be noted that endometrial colonization (endometrialization) can also occur in the interstitial (25%) or isthmic (10%) portions of the FT as variation of normality. With this variant, cyclical hemorrhage can cause hematosalpinx, leading to infertility and ectopic gestation. None of these effects were seen in the index case.
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REFERENCES
1. Smolarz B, Szyłło K, Romanowicz H. Endometriosis:Epidemiology, classification, pathogenesis, treatment and genetics (Review of literature). Int J Mol Sci 2021;22:10554.
2. Prodromidou A, Kathopoulis N, Zacharakis D, Grigoriadis T, Chatzipapas I, Protopapas A. Tubal endometriosis:From bench to bedside, A scoping review. J Pers Med 2022;12:362.
3. Hill CJ, Fakhreldin M, Maclean A, Dobson L, Nancarrow L, Bradfield A, et al. Endometriosis and the fallopian tubes:Theories of origin and clinical implications. J Clin Med 2020;9:1905.
