A case of decidualized scar endometriosis with pronounced myxoid change including signet ring-like cells is presented and discussed in the light of relevant literature.
Macroscopically 3x2x2 cm circumscribed gray-white lesion with gelatinous areas was noted (Figure 1). Microscopically lobular pattern separated by fibrous septa was observed. Each lobule contained cystic spaces (Figure 2A) lined with single layer of atrophic cells with no cytoplasm, resembling endothelium of lymphatic vessels. Loosely cohesive, vacuolated signet ring-like cells embedded in myxoid stroma were also noted (Figure 2B). However, no mitotic activity or nuclear atypia was seen.
Figure 1: Macroscopic view of the gray-white gelatinous mass.
Histochemically, alcian blue test was positive in myxoid areas and vacuolated cells but PAS staining was negative. Immunohistochemically; vimentin (1/100,V9, Neomarkers, Fremont, CA, USA), S-100 (1/100, 4C4.9, Neomarkers, Fremont, CA, USA), keratin (1/100, AE1/ AE3, Neomarkers, Fremont, CA, USA) and CD 34 (1/100, QBEnd, Neomarkers, Fremont, CA, USA), CD 10 (1/30, Ab-2 clone 56C6, Neomarkers, Fremont, CA, USA) stainings were performed. Vimentin was strongly positive in vacuolated signet ring-like cells (decidual cells), CD10 was also focally positive in the cell membranes of the decidualized cells, but keratin, S-100 and CD 34 tests were negative. Atrophic lining cells of cystic spaces were positive for keratin (Figure 3A) and negative for CD 34 (Figure 3B). The histopathological diagnosis was decidualized scar endometriosis with myxoid change.
There are few reported cases with "myxoid change endometriosis” in the literature. Three of them were seen in nonpregnant[2,4,6] and two in pregnant patients[3,5]. In the present case patient was pregnant and had a history of cesarean section (Table 1).
Table 1: Clinico-pathological features of previous reported cases.
Myxoid change in endometriosis could be misinterpreted as a neoplasm, clinically and histologically, especially during frozen section.
Hameed et al.[6] and Clement et al.[2] reported endometriosis with myxoid change in a nonpregnant patient, whose frozen section examination caused confusion with mucinous adenocarcinoma and pseudomyxoma peritonei. Ying et al.[4] also described myxoid change associated with endometriosis in a nonpregnant patient who had cesarean section one year ago. Histological findings showed foci of large irregular endometrial glands embedded in myxoid stroma and acellular mucin pools, presenting as a pseudomalignancy.
Ying et al.[4] hypothesized these myxoid changes as a cyclic, hormone driven, predecidual stroma altered during the menstrual cycle. In case of pregnancy some authors related the changes as a form of altered decidua. When associated with a scar, the lesion arises as a result of iatrogenic mechanical implantation.
Mc Cluggage[5] and Nogales[3] reported cases of endometriosis with myxoid change in pregnant patients. The presenting features in our case were similar to the findings of Nogales et al.[3], because both of these patients developed a mass at the scar tissue of cesarean section. In case of Cluggage[5] although patient was pregnant, the site of endometriosis was unusually localized in the groin. Histological findings were similar being abundant myxoid change with marked decidualization and calcification. Suspicion for malignancies like soft tissue sarcoma, mucinous adenocarcinoma and variety of benign and malignant mesenchymal myxoid lesions were taken into consideration. The authors pointed out that myxoid change in this case may be degenerative in nature and related to pregnancy. In our case, there was no calcification.
Differential diagnosis is particulary important during intraoperative consultation. Myxoid stroma, vacuolated cells could cause misinterpretation[2]. In this situation, recognizing the absence of characteristic signs of malignancy such as nuclear atypia and mitosis prevents overdiagnosis. Histochemical and immunohistochemical studies can be helpful for routine interpretation. In signet ring cell carcinoma, PAS strongly stains the cytoplasmic vacuoles whereas the decidual cells are PASnegative. Immunohistochemically, decidual cells are strongly vimentin positive while mucinous carcinoma cells are not. Also keratin stains negatively in decidua but positively in carcinoma. In our case vimentin was strongly positive in vacuolated (decidual) cells. CD10, as an important marker for endometrial stroma, was also positive in the cell membranes of the decidualized cells, but keratin expression was negative.
As a result; although the histologic diagnosis of endometriosis is usually easy, diagnostic problems can occur as a result of alterations or absence of glandular or stromal components, or when secondary changes are present, especially myxoid change which is rarely seen and not very well known by pathologists. It can be confused with neoplasm clinically and histologically. A special care should be taken while taking patients' obstetrical and surgical history and examining their pathology specimens. Also immunohistochemical and conventional histochemical tests may also help in differential diagnosis.
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Endometriosis with myxoid change. A case simulating
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Myxoid Change in decidualized scar endometiosis
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