Endosalpingiosis in axillary lymph nodes: a possible pitfall in the staging of patients with breast carcinoma

Our series includes 3 women who underwent SLN biopsy in the course of staging for ipsilateral breast carcinoma. Two of the 3 patients underwent surgical excision of the primary tumor together with SLN biopsy at our center. All SLNs were processed according to our routine protocol, which includes hematoxylin and eosin (H&E)-stained level sections and immunoperoxidase stains for cytokeratins. The third patient underwent staging for breast carcinoma at an outside hospital and we received standard H&E-stained slides of her primary tumor for review, together with all the slides of the SLN and of the subsequent axillary lymph node dissection (ALND); 5 unstained slides of the SLN with endosalpingiosis were also obtained for immunoperoxidase studies. We performed immunohistochemical stains for myoepithelial and müllerian markers on all cases, as well as for cytokeratin AE1:AE3, calretinin, CA125, and collagen IV on some, using conventional avidin-biotin peroxidase technique on an automated immunostainer (Ventana Medical System, Inc, Tucson, AZ) according to the manufacture's protocols (Ventana Medical System, Inc). Table 1 summarizes antigens, reagents, and immunoperoxidase staining protocols. Three pathologists (A.C., K.G., and E.B.) reviewed representative slides of the primary breast carcinomas, and all slides and immunoperoxidase stains of the SLNs of the 3 patients. Case Reports Patient 1 Clinical History: A 75-year-old woman presented to our center in 2003 for evaluation of mammographic calcifications in the upper outer quadrant of the right breast. The patient was otherwise in good health, with no significant personal medical or surgical history and no known family history of breast or ovarian cancer. Pathologic Findings: A right breast stereotactic core biopsy revealed ductal carcinoma in situ (DCIS), solid type, with high nuclear grade, extensive necrosis, and associated calcifications. The surgical excision specimen contained extensive DCIS, solid and cribriform types, with high nuclear grade, necrosis and associated calcifications. DCIS was adjacent to the biopsy site and close (<0.1 cm) to the inked margin at multiple foci. No definitive evidence of (micro)invasion or lymphovascular invasion was identified. At the time of the surgical excision, the patient also underwent SLN biopsy. Three SLNs and 2 non-SLNs were submitted for routine pathologic examination, without intraoperative evaluation. Few (at least 6) benign glandular inclusions with the typical morphology of endosalpingiosis were identified within the lymph node capsule and in the lymph node sinuses (at least 3 glands) (Fig. 1A). The remaining lymph nodes, including the 2 SLNs, did not contain carcinoma or endosalpingiosis. Clinical Follow-up: The patient underwent surgical re-excision for close margins and no additional carcinoma was found. After surgery, the patient received radiation. She is alive with no evidence of disease (NED) 80 months after surgery. Patient 2 Clinical History: A 65-year-old woman noticed a mass in her left breast in October 2007 and a mammogram demonstrated a suspicious lesion in the upper inner quadrant. The patient underwent lumpectomy with SLN biopsy at an outside institution and 1 SLN was identified and submitted for intraoperative evaluation; no metastatic carcinoma or other lesion was present in the frozen section slide. Pathologic Findings: According to the submitted gross description, the lumpectomy specimen contained a 1.8 cm solid tan-pink irregular mass, corresponding microscopically to a moderately differentiated invasive ductal carcinoma (Fig. 2A) associated with solid and cribriform DCIS, with intermediate nuclear grade. Per report, the invasive carcinoma was estrogen and progesterone receptor positive, and HER2 negative. Two subcapsular glands measuring 0.2 and 0.3 mm respectively were noted in the permanent H&E sections of the SLN and were interpreted as metastatic ductal carcinoma at the outside center. Three months later the patient underwent ALND at the same hospital, with removal of 19 lymph nodes, all of which were negative for malignancy. On the basis of the diagnosis of micrometastatic carcinoma, a local oncologist recommended adjuvant chemotherapy. At this point the patient presented to our center for a second opinion regarding management of her case. We reviewed the submitted H&E slides of the SLN and rendered the diagnosis of endosalpingiosis (Fig. 2B). Ancillary immunoperoxidase stains for WT1 and PAX8 performed on submitted unstained sections supported the latter morphologic diagnosis. The diagnosis of invasive and in situ ductal carcinoma was confirmed. Clinical Follow-up: The patient is currently followed at our center. Thirty months after the surgery, she has no evidence of disease, but she has developed moderate lymphedema with some limitation in the left arm movements and axillary pain syndrome. She takes letrozole under the care of one of our medical oncologists and reports no adverse side effects. Patient 3 Clinical History: In 2008, a routine mammogram demonstrated a spiculated density in the upper outer quadrant of the right breast of a 66-year-old woman. A follow-up ultrasound detected a 1.4 cm solid mass. The patient had chronic hypertension and no other significant personal or familial clinical history. Pathologic Findings: A right breast core needle biopsy of the mass demonstrated cribriform DCIS with low nuclear grade, focally involving a sclerosing intraductal papilloma. Excision of the lesion revealed a soft and tan nodule measuring 0.9×0.8×0.8 cm, adjacent to biopsy site changes. Microscopically, focal markedly atypical ductal hyperplasia was identified in association with a 0.9 cm intraductal papilloma. Three SLNs had been submitted for permanent sections and 1 contained endosalpingiosis. At least 10 benign appearing glands were distributed within the capsule (Fig. 1B) and a few more were present focally in the lymph node parenchyma. Clinical Follow-up: The patient is doing well with no evidence of recurrent disease 24 months after surgery. Morphologic and Immunohistochemical Findings In H&E-stained sections, the SLNs involved by endosalpingiosis contained 2 to 10 small glands lined by a monolayer of cuboidal to tall columnar epithelial cells. Few cells displayed terminal bars with cilia (Fig. 3A), others (intercalated cells) had abundant clear cytoplasm and were wedged in between the columnar cells (Fig. 1B). The nuclei were elongated to oval, and euchromatic with inconspicuous nucleoli. No periglandular endometrial-type stroma or myoepithelium was present around the glands. The cells showed no cytologic atypia and no mitotic activity, and did not morphologically resemble the primary tumors in any of the 3 cases. Lack of a myoepithelial layer around the endosalpingiotic glands was confirmed by negative immunoreactivity for myoepithelial markers, including calponin (all 3 patients), and 4A4/p63 (patients 2 and 3). We also demonstrated absence of basement membrane around the glands by negative immunoreactivity for collagen IV in 1 case (patient 3). Conversely, we documented strong nuclear positivity for WT1 and PAX8 in the glands of all 3 patients, consistent with müllerian origin (Figs. 3B, C). The glands were strongly immunoreactive for cytokeratin AE1:AE3 (patients 1 and 3) (Fig. 3D), and negative for CA125 and calretinin (patient 1). The clinicopathologic and immunohistochemical data of the 3 patients are summarized in Table 2.

Dissection of ALND results in limitations of arm movement, chronic pain, and paresthesia in about one-fourth of the patients, with consequent negative impact on quality of life. In the past decade, SLN biopsy has been established as a new standard of care for staging of breast cancer patients and its improved accuracy is associated with significantly reduced morbidity. Intraoperative pathologic examination of SLNs is performed at many centers. The best method for accurate intraoperative evaluation remains subject of debate, even though various techniques, recently including real time-polymerase chain reaction-based methods, seem to show similar overall efficacy and accuracy. Intraoperative identification of carcinoma in an SLN usually leads to immediate ALND. False-positive results are rare, but some report incidence in up to 3.7% of cases. A false-positive diagnosis, whether rendered intraoperatively or on review of permanent sections, will result in unnecessary ALND with increased morbidity and reduced quality of life. Benign inclusions commonly found in axillary lymph nodes are the most frequent cause of false-positive diagnosis. These include capsular nevi, epithelial cysts and, most common of all, heterotopic mammary glands. We report here 3 patients in whom endosalpingiosis simulated axillary lymph node metastasis of breast carcinoma, adding to the list of possible pitfalls. Endosalpingiosis in pelvic and retroperitoneal lymph nodes is a well-documented finding, and so is its potential to mimic metastatic carcinoma, but its presence in supradiaphragmatic lymph nodes is rare and usually restricted to the mediastinum. To the best of our knowledge, only 2 prior case reports have documented endosalpingiosis in lymph nodes obtained during staging of patients with mammary carcinoma. In 1 case, endosalpingiosis constituted an inconsequential finding in the axillary SLN of a 44-year-old woman, as metastatic carcinoma was also present in the same node. The other report concerned an 84-year-old woman with endosalpingiosis involving 1 out of 2 axillary SLNs. The benign glands were interpreted intraoperatively as metastatic carcinoma, and this diagnosis was followed by immediate ALND. Even though endosalpingiosis was correctly diagnosed on review of the permanent slides, the patient underwent unnecessary axillary surgery. Endosalpingiosis was misdiagnosed as metastatic carcinoma at an outside center also in 1 of the 3 women in our series (patient 2), and the patient had subsequent ALND with removal of 19 additional benign lymph nodes. Furthermore, because the patient carried a diagnosis of micrometastatic carcinoma, her treatment recommendations included adjuvant chemotherapy. Only upon review of the slides for a second opinion, endosalpingiosis was recognized and the patient was spared unnecessary chemotherapy. Taken together, these cases underscore the diagnostic challenges posed by endosalpingiosis when it involves the axillary lymph nodes of patients with breast carcinoma and the severe clinical implications of its misdiagnosis, ranging from potentially harmful surgery to inaccurate staging and overtreatment with adjuvant chemotherapy. Involvement of supradiaphragmatic lymph nodes by endosalpingiosis is rare. First used by Sampson in 1930, the term endosalpingiosis designates heterotopic glands lined by benign epithelium recapitulating the normal mucosa of the fallopian tube. The terms paramesonephric or müllerian inclusions with tubal-type epithelium are also used to refer to the same lesion. Histologically, the glands of endosalpingiosis are lined by ciliated, nonciliated, and intercalated “peg” cells arranged in a monolayer, just as in the normal fallopian tube. The epithelium can also form papillae of varied complexity, with or without associated psammoma bodies. The etiology of endosalpingiosis still remains unclear. According to the most commonly accepted view, pelvic peritoneal mesothelium and submesothelium (also known as secondary or extended müllerian system) can undergo müllerian metaplasia and form either benign glands (endosalpingiosis) or carcinomas histologically indistinguishable from those arising in the ovary and fallopian tube. Other theories put forward to explain the histogenesis of endosalpingiosis outside the fallopian tube include peritoneal implantation of sloughed tubal epithelium, surgical displacement, and lymphatic dissemination of tubal mucosa. None of these hypotheses necessarily excludes the others and more than 1 process could play a role in the pathogenesis of this benign lesion. Benign glandular inclusions in lymph nodes can usually be distinguished from metastatic carcinoma by morphologic comparison with the primary tumor. Even if no slides of the latter are available, lack of cytologic atypia is usually sufficient for correct classification. In particular, finding cells with terminal bars and cilia admixed with intercalated “peg” cells with ovoid shape and clear cytoplasm provides sufficient and distinctive evidence to support the morphologic diagnosis of endosalpingiosis. The work-up of SLNs includes immunoperoxidase stains for cytokeratins at many centers, and this could prompt misdiagnosis of endosalpingiosis as metastatic carcinoma, if the results of immunoperoxidase stains are interpreted without paying close attention to the morphology of the cytokeratin-positive cells. The results of immunoperoxidase stains performed to rule out benign mammary inclusions could also be misleading, because endosalpingiosis lacks myoepithelium as well as basement membrane. Immunoperoxidase stains useful to support the diagnosis of endosalpingiosis include PAX8, a transcription factor involved in the development of thyroid, kidney and müllerian system, and its downstream molecule WT1. In the appropriate setting, positive immunoreactivity for either one or both of these markers supports ovarian/müllerian origin. It is also worth noting that testing for estrogen or progesterone receptor expression will not assist in the differential diagnosis between mammary carcinoma and benign müllerian glands, as both are usually positive for these markers. Our experience demonstrates that the correct diagnosis of endosalpingiosis in axillary lymph nodes rests first and foremost on morphology and awareness of this lesion is critical for its correct classification. Although rare, endosalpingiosis needs to be included among the morphologic mimics of metastatic carcinoma to avoid its misdiagnosis and possible overstaging and overtreatment of patients.

- 1. Brogi E, Torres-Matundan E, Tan LK, et al. The results of frozen section, touch preparation, and cytological smear are comparable for intraoperative examination of sentinel lymph nodes: a study in 133 breast cancer patients. Ann Surg Oncol. 2005;12:173–180. - 2. Burmeister RE, Fechner RE, Franklin RR. Endosalpingiosis of the peritoneum. Obstet Gynecol. 1969;34:310–318. - 3. Cajigas A, Axiotis CA. Endosalpingiosis of the vermiform appendix. Int J Gynecol Pathol. 1990;9:291–295. - 4. Clement PB. Endometriosis, secondary mullerian lesions, and mesothelial proliferations. In: Kurman RJ, ed. Blaustein's Pathology of the Female Genital Tract. New York, NY: Springer-Verlag; 1987:516–559. - 5. Dore N, Landry M, Cadotte M, et al. Cutaneous Endosalpingiosis. Arch Dermatol. 1980;116:909–912. - 6. Edlow DW, Carter D. Heterotopic epithelium in axillary lymph nodes: report of a case and review of the literature. Am J Clin Pathol. 1973;59:666–673. - 7. Farhi DC, Silverberg SG. Pseudometastases in female genital cancer. Pathol Annu. 1982;17:47–76. - 8. Fisher CJ, Hill S, Millis RR. Benign lymph node inclusions mimicking metastatic carcinoma. J Clin Pathol. 1994;47:245–247. - 9. Fortunato L, Amini M, Farina M, et al. Intraoperative examination of sentinel nodes in breast cancer: is the glass half full or half empty? Ann Surg Oncol. 2004;11:1005–1010. - 10. Garret R, Ada AE. Epithelial inclusion cysts in an axillary lymph node; report of a case simulating metastatic adenocarcinoma. Cancer. 1957;10:173–178. - 11. Giuliano AE, Dale PS, Turner RR, et al. Improved axillary staging of breast cancer with sentinel lymphadenectomy. Ann Surg. 1995;222:394–399; discussion 399–401. - 12. Henley JD, Michael HB, English GW, et al. Benign mullerian lymph node inclusions. An unusual case with implications for pathogenesis and review of the literature. Arch Pathol Lab Med. 1995;119:841–844. - 13. Henry-Tillman RS, Korourian S, Rubio IT, et al. Intraoperative touch preparation for sentinel lymph node biopsy: a 4-year experience. Ann Surg Oncol. 2002;9:333–339. - 14. Holdsworth PJ, Hopkinson JM, Leveson SH. Benign axillary epithelial lymph node inclusions--a histological pitfall. Histopathology. 1988;13:226–228. - 15. Horn LC, Bilek K. Frequency and histogenesis of pelvic retroperitoneal lymph node inclusions of the female genital tract. An immunohistochemical study of 34 cases. Pathol Res Pract. 1995;191:991–996. - 16. Karp LA, Czernobilsky B. Glandular inclusions in pelvic and abdominal para-aortic lymph nodes. A study of autopsy and surgical material in males and females. Am J Clin Pathol. 1969;52:212–218. - 17. Lauchlan SC. The secondary Mullerian system. Obstet Gynecol Surv. 1972;27:133–146. - 18. Layfield LJ, Mooney E. Heterotopic Epithelium in an Intramammary Lymph Node. Breast J. 2000;6:63–67. - 19. Maiorano E, Mazzarol GM, Pruneri G, et al. Ectopic breast tissue as a possible cause of false-positive axillary sentinel lymph node biopsies. Am J Surg Pathol. 2003;27:513–518. - 20. Mitchell ML. Frozen section diagnosis for axillary sentinel lymph nodes: the first six years. Mod Pathol. 2005;18:58–61. - 21. Norton LE, Komenaka IK, Emerson RE, et al. Benign glandular inclusions a rare cause of a false positive sentinel node. J Surg Oncol. 2007;95:593–596. - 22. Osmond R, Kalinovsky P. Epithelial inclusion cysts in axillary nodes associated with malignant disease. Med J Aust. 1972;2:834–836. - 23. Piana S, Asioli S, Cavazza A. Benign Mullerian inclusions coexisting with breast metastatic carcinoma in an axillary lymph node. Virchows Arch. 2005;446:467–469. - 24. Pickartz H. Tumor-like lesions of the secondary mullerian system. Immunohistochemical investigations and differential diagnosis. APMIS Suppl. 1991;23:146–151. - 25. Resetkova E, Hoda SA, Clarke JL, et al. Benign heterotopic epithelial inclusions in axillary lymph nodes. Histological and immunohistochemical patterns. Arch Pathol Lab Med. 2003;127:e25–e27. - 26. Sampson JA. Postsalpingectomy endometriosis (endosalpingiosis). Am J Obstet Gynecol. 1930;20:443–480. - 27. Shousha S. An unusual breast cyst. Histopathology. 1989;14:423–425. - 28. Silton RM. More glandular inclusions. Am J Surg Pathol. 1979;3:285–286. - 29. Turner DR, Millis RR. Breast tissue inclusions in axillary lymph nodes. Histopathology. 1980;4:631–636. - 30. Veronesi U, Paganelli G, Viale G, et al. A randomized comparison of sentinel-node biopsy with routine axillary dissection in breast cancer. N Engl J Med. 2003;349:546–553. - 31. Veys I, Durbecq V, Majjaj S, et al. Eighteen months clinical experience with the GeneSearch breast lymph node assay. Am J Surg. 2009;198:203–209. - 32. Zynger DL, McCallum JC, Everton MJ, et al. Paracortical axillary sentinel lymph node ectopic breast tissue. Pathol Res Pract. 2009;205:427–432.